ACDC MCQ

Question Bank in DC Circuits A. DC CIRCUITS: BASIC PRINCIPLES 1. REE Board Exam March 1998 The substation bus bar is made up of 2 inches round copper bars 20 ft long. What is the resistance of each bar if resistivity is 1.724 x 10-6 ohm-cm. A. 7.21 x 10-5 Ω C. 5.185 x 10-5 Ω B. 13.8 x 10-6 Ω D. 2.96 x 10-5 Ω 2.

3.

4.

REE October 1997 Determine the resistance of a busbar made of copper if the length is 10 meters long and the cross section is a 4 x 4 cm2. Use 1.7241 micro ohm-cm as the resistivity. A. 2.121 x 10-4 Ω C. 3.431 x 10-5 Ω B. 4.312 x 10-4 Ω D. 1.078 x 10-4 Ω EE Board Exam October 1991 One turn of a copper bar is produced by cutting copper washer along a radius and spreading the ends. The washer is cut from soft drawn copper having a resistivity at 20°C of 1.732 x 10-6 ohm-cm. The washer is 0.125 inch thick and has inside diameter and outside diameter of 1 inch and 9 inches respectively. Calculate the exact resistance between the two ends of the turn to direct current, taking into account the non-uniform current distribution. Assume the contact along the ends of the turn to be perfect over the entire cross section. A. 12.74 x 10-6 Ω C. 17.22 x 10-6 Ω -6 B. 15.53 x 10 Ω D. 14.83 x 10-6 Ω EE Board Exam October 1990 Determine the resistance of a conductor 0.10 m long, with a uniform diameter of 1.0 cm and having a resistivity which varies as a function of length L measured from the one end of the conductor according to ρ = 0.003 + 10-4 L2 ohm-cm. A. 0.0852 ohm C. 0.0806 ohm B. 0.0915 ohm D. 0.0902 ohm

5.

EE Board Exam April 1992 A coil has 6,000 turns of wire and a resistance of 380 ohms. The coil is rewound with the same quantity (weight) of wire, but has 13,400 turns. How many ohms will the new coil have? A. 1895 ohms C. 1792 ohms B. 1825 ohms D. 1905 ohms

6.

EE Board Exam April 1992 A copper wire of unknown length has a resistance of 0.80 ohm. By successive passes through drawing dies, the length of the wire is increased by 2 ½ times its original value. Assuming that resistivity remains unchanged during the drawing process, determine the new value of its resistance. A. 4 ohms C. 5 ohms B. 3 ohms D. 6 ohms

7.

REE Board Exam October 1998 A one-meter rod of 2-cm diameter is drawn until its resistance is 100 times the initial resistance. Its length afterwards is? A. 10 m C. 12.5 m B. 100 m D. 5 m

8.

EE Board Exam April 1993 A kilometer of wire having a diameter of 11.7 mm and a resistance of 0.031 ohm is drawn down so that its diameter is 5.0 mm. What does its resistance become? A. 0.85 ohm C. 0.93 ohm B. 0.78 ohm D. 0.81 ohm

9.

EE Board Exam April 1995 A certain wire has a resistance R. The resistance of another wire identical with the first except for having twice its diameter is A. 4R C. 2R B. R/2 D. R/4

10. REE Board Exam October 1996 What is the size in square millimeter (mm2) is the cable of 250 MCM size? A. 118.656 mm2 C. 112.565 mm2 2 B. 126.675 mm D. 132.348 mm2 11. REE Board Exam October 1998, September 2001 The resistance of a copper wire at 30°C is 50 ohms. If the temperature coefficient of copper at 0°C is 0.00427, what is the resistance at 100°C? A. 72.26 ohms C. 63.24 ohms B. 54.25 ohms D. 58.15 ohms 12. REE Board Exam March 1998 The resistance of a wire is 126.48 Ω at 100°C and 100 Ω at 30°C. Determine the temperature coefficient of copper at 0°C. A. 0.00427/°C C. 0.0256/°C B. 0.00615/°C D. 0.365/°C 13. EE Board Exam October 1991 Two heating elements which is 500 ohms and 250 ohms are connected in series with temperature coefficients of 0.001 and 0.003 ohms per °C, respectively at 20°C. Calculate the effective temperature coefficient of the combination. A. 0.00215 C. 0.00712 B. 0.00626 D. 0.00167 14. EE Board Exam October 1992 The insulation resistance of a kilometer of the cable having a diameter of 2 cm and an insulation thickness of 2 cm is 600 ohms. If the thickness of the insulation is increased to 3 cm, find the insulation resistance of the cable. A, 725 ohms C. 757 ohms B. 850 ohms D. 828 ohms 15. EE Board Exam April 1989 It is required that a loading of 3 kW be maintained in a heating element at an initial temperature of 20°C,

a voltage of 220 V is necessary for the purpose. After the element has settled down to steady state, it is found that a voltage of 240 volts is necessary to maintain the 3 kW loading. The element resistance temperature coefficient is 0.0006 per degree centigrade at 20°C. Calculate the final temperature of the heating element. A. 345.43°C C. 336.84°C B. 326.42°C D. 318.48°C 16. REE Board Exam October 1999 How long must a current of 5 A pass through a 10 ohm resistor until a charge of 12000 coulomb passes through? A. 1 min C. 3 min B. 2 min D. 4 min

B.

8.14 μΩ

D.

0.814 μΩ

24. REE Board Exam April 2001 The resistance of the field winding of a DC machine is 0.25 Ω at 25°C. When operating at full-load, the temperature of the winding is 75°C. The temperature coefficient of resistance of copper is 0.00427 per °C at 0°C. Find the resistance of the field winding at fullload. A. 0.298 Ω C. 0.512 Ω B. 0.315 Ω D. 0.271 Ω 25. REE Board Exam October 2000 A coil of copper has resistance of 5.46 Ω at 75°C. What will be its resistance at 25°C? A. 4.58 Ω C. 5.02 Ω B. 4.84 Ω D. 4.35 Ω

17. REE Board Exam October 1999 What is the power required to transfer 97,000 coulombs of charge through a potential rise of 50 volts in one hour? A. 0.5 kW C. 1.3 kW B. 0.9 kW D. 2.8 kW

26. REE Board Exam April 2001 A certain generator generates 1,500,000 joules per minute. What is the output in kW? A. 50 C. 25 B. 500 D. 125

18. REE Board Exam April 2001 A round wire has 250 MCM. Find its diameter in inches. A. ½ C. 0.16 B. ¼ D. 0.08

27. ECE BOARD NOV 2001 _____ is anything that has weight had occupies space. It may be solid, liquid or gas. A. Amalgam C. Matter B. Alloy D. Compound

19. REE Board Exam September 2003 In the American wire gauge, as the number of gauge increases, the diameter of wire ____ A. increases B. decreases C. does not change D. become twice

28. ECE Board Exam April 2000 It is defined as anything that occupies space and has weight. A. atom C. molecule B. compound D. matter

20. REE Board Exam September 2003 In cgs system, what is the unit of emf where I is in abampere and P is in erg per second? A. millivolt C. abvolt B. kilovolt D. volt 21. REE Board Exam September 2002 One (1) kW is equal to ____ hp. A. 0.746 C. 550 B. 1.34 D. 1.5 22. REE Board Exam October 1998 Two copper conductors have equal length. The cross-sectional area of one conductor is three times that of the other. If the resistance of the conductor having smaller cross-sectional area is 20 Ω, what is the resistance of the other? A. 20/3 Ω C. 180 Ω B. 60 Ω D. 20/9 Ω 23. REE Board Exam October 2000 A copper bar has a length of 20 ft., width of 4 inches and thickness of 0.5 inch. If the resistivity of copper is 10.37 Ω-CM/ft, what is the resistance of the bar? A. 81.4 μΩ C. 814 μΩ

29. ECE Board Exam November 1999 The lightest kind of atom or element A. hydrogen C. titanium B. helium D. oxygen 30. ECE Board Exam November 1998 In order to have a good conductor material, such material shall have _____ valence electrons. A. one C. more than ten B. five D. twenty one 31. ECE Board Exam November 1997 Electric power refers to _____ A. volt ampere C. volt coulomb B. watt second D. joule 32. ECE Board Exam November 1995 What composes all matter whether a liquid, solid or gas? A. electrons C. protons B. atoms D. neutrons 33. ECE Board Exam November 2001 What is a physical combination of compounds or elements NOT chemically combined that can be separated by physical means? A. substance C. mixture

B.

atom

D.

molecule

34. ECE Board Exam April 1998 Determine the equivalent work of 166 watt-second. A. 10 joules C. 16.6 joules B. 100 joules D. 166 joules 35. ECE Board Exam November 2001 One of the following is the best conductor of electricity. A. Air C. Carbon B. Copper D. Silicon 36. ECE Board Exam November 1999 What is the basic unit for measuring current flow? A. coulomb C. volt B. ampere D. atomic weight 37. ECE Board Exam November 1995 ______ has a unit of electron volt A. Energy C. Current B. Potential difference D. Charge 38. ECE Board Exam November 2001 The motion of charged particles especially colloidal particles through a relative stationary liquid under the influence of an applied electric provided. A. hysteresis C. electrophoresis B. electrolysis D. electro analysis 39. ECE Board Exam April 2001 What is a symbol that represents a quantity or a single object? A. unit C. item B. number D. base 40. ECE Board Exam April 2000 Determine which of the following has the least number of electrons found at the outer shell. A. semi-insulator C. semiconductor B. insulator D. conductor 41. ECE Board Exam April 2001 The term describes a material whose resistance remains relatively constant with changes in temperature A. positive temperature coefficient B. negative temperature coefficient C. neutral temperature coefficient D. zero temperature coefficient 42. ECE Board Exam November 1998 Resulting effect when electron is made to move A. dynamic electricity C. lines of force B. static electricity D. magnetic lines 43. ECE Board Exam November 1997 One of the following characteristics of a resistive material which do not change its resistive value with respect to time is its _____ A. fidelity C. stability B. sensitivity D. selectivity

44. ECE Board Exam November 2001 What do you call the element that conducts electricity very readily? A. semi-conductors C. insulators B. conductors D. dielectric 45. ECE Board Exam April 2001 Which of the following material is referred to as a medium whereby electrons can move easily from atom to atom? A. insulator C. mica B. dielectric D. conductor 46. ECE Board Exam November 2001 A chemical combination of elements can be separated by chemical means but not by physical means. It is created by chemically combining two or more elements. A. molecules C. matter B. compound D. mixture 47. ECE Board Exam April 2000 A substance which cannot be reduced to a simpler substance by chemical means A. atom C. matter B. molecule D. element 48. ECE Board Exam November 2001 Calculate the equivalent power in watt of 100 joules per second. A. 1.66 watts C. 16.66 watts B. 100 watts D. 1,000 watts 49. ECE Board Exam April 2001 It is a neutral particle that has no electrical charge. A. atom C. electron B. proton D. neutron 50. ECE Board Exam November 1999 Which material has more free electrons? A. mica C. conductor B. insulator D. dielectric 51. ECE Board Exam November 2001 The new and preferred term for conductance or mho A. Siemens C. Seaman B. She-man D. ROM 52. ECE Board Exam April 2001 Represents the current flow produced by one volt working across one ohm of resistance. A. resistance B. ampere C. voltage D. electromotive force 53. ECE Board Exam November 1995 When an atom gains an additional _____, it results to a negative ion. A. atom C. proton B. neutron D. electron 54. ECE Board Exam November 1999

The definite discrete amount of energy required to move an electron from a lower shell to higher shell. A. quantum B. positive energy C. negative energy D. quanta 55. ECE Board Exam November 1999 What will happen to an atom if an electron is either taken out or taken into the same atom? A. becomes a negative ion B. becomes an ion C. becomes a positive ion D. nothing will happen 56. ECE Board Exam April 1999 The energy in an electron that is called the energy of motion A. electromotive force B. kinematics C. kinetic energy D. potential energy 57. ECE Board Exam November 1996 Electric charge of neutron is the same as ______. A. atom C. current B. electron D. proton 58. ECE Board Exam April 1998 Ion is _____. A. free electron B. nucleus without protons C. proton D. an atom with unbalanced charges 59. ECE Board Exam November 1997 An insulating element or material has capability of _____. A. storing voltage B. preventing short circuit between two conducting wires C. conducting large current D. storing high current 60. ECE Board Exam April 1998 What is the value of a resistor with colors from left: Orange, Blue, Gold and Silver? A. 34 ohms + /-10% B. 36 ohms +/-10% C. 3.4 ohms +/-10% D. 3.6 0hms +/-10% 61. ECE Board Exam April 2001 A three-terminal resistor with one or more sliding contacts which functions as an adjustable voltage divider A. Rheostat C. Potentiometer B. Bleeder resistor D. Voltage divider 62. ECE Board Exam November 2000 A resistor which is used to draw a fixed amount of current A. potentiometer C. fixed resistor

B.

bleeder resistor

D.

rheostat

63. ECE Board Exam November 2001 Find the value of a resistor with the following color codes: Orange, Yellow, Red, Red A. 34 k ohms +/-5% B. 3.4 ohms +/-2% C. 3.4 k ohms +/-10% D. 34 k ohms +/-20% 64. ECE Board Exam November 1996 Electric energy refers to ______. A. Joules divided by time C. Watt B. Volt-ampere D. Volt-coulomb 65. ECE Board Exam April 2001 What is the resistance of an open fuse circuit? A. at least 1000 ohms B. infinity C. zero D. 100 ohms at standard temperature 66. ECE Board Exam April 1998 When should a fuse be replaced with a higher rated unit? A. when the fuse of the original value is small in size B. when the original is not available C. never D. if it blows 67. ECE Board Exam November 2000 The ability to do work A. energy C. potential B. kinetic D. voltage 68. ECE Board Exam November 2001 Which type of variable resistor should you use for controlling large amount of current? A. Potentiometer C. Variac B. Adjustable wirewound D. Rheostat 69. ECE Board Exam April 2000 What does the fourth loop of an electronic resistor color code represent? A. Multiplier B. Temperature C. First digit of the equivalent value D. Tolerance 70. ECE Board Exam November 2000 Ten micro-microfarads is equivalent to _____ A. 100 picofarads B. 100 nanofarad C. 1000 milli microfarad D. 10.0 picofarads 71. ECE Board Exam November 1995 How much is the resistance of a germanium slag 10 cm long and cross sectional area of 1 square cm? A. 55 k ohms C. 550 k ohms B. 5.5 k ohms D. 550 ohms

72. ECE Board Exam November 2001 A variable resistor normally used as a voltage divider A. Carbon film resistor B. Potentiometer C. Adjustable resistor D. Metal film resistor

What is the value of a resistor having the following colored bands: Yellow-Gray-Red-Silver? A. 4800 ohms ±10% B. 480 ohms ±10% C. 3800 ohms ±1% D. 4.8 ohms ±1%

73. ECE Board Exam April 2001 Determine the equivalent horse power of 2.611 kilowatts. A. 3.50 hp C. 2.25 hp B. 2.50 hp D. 1.50 hp

82. ECE Board Exam November 1997 Find the value of resistor with the following color codes; Brown, White, Orange, Red A. 190 ohms 10% B. 19 k ohms 2% C. 1.9 k ohms 10% D. 19 k ohms 20%

74. ECE Board Exam November 2000 Find the lowest resistance value of the following resistors. A. White, black, black B. Violet, gray, yellow, silver C. Red, black, gold D. Gray, gray, black 75. ECE Board Exam November 1998 If the bands on a resistor are yellow, violet, red and gold, what is the resistance value? A. 470 ohms 5% B. 470 ohms 10% C. 47000 ohms 5% D. 4700 ohms 5% 76. ECE Board Exam November 1997 Rust in electrical (wire) connections will result to _____ A. Conductance C. Voltage B. Resistance D. Inductance 77. ECE Board Exam November 1996 The area of a conductor whose diameter is 0.001 inch is equal to A. One micron C. One circular mil B. One angstrom D. One steradian 78. ECE Board Exam November 1995 _____ is the term used to express the amount of electrical energy in an electrostatic field. A. Joule C. Volt B. Coulomb D. Watt 79. ECE Board Exam November 1995 Which of the following statement is correct? A. Potentiometer has two terminals B. Transistor has two terminals C. Typical power rating of a carbon-composition resistor ranged from 0.125 W to 2 W D. Open resistor has small resistance 80. ECE Board Exam November 1996 _____ is one factor that does not affect resistance. A. Resistivity C. Length B. Cross sectional area D. Mass 81. ECE Board Exam November 1998

83. ECE Board Exam November 1998 Resistor with colored bands in the body A. Adjustable resistor B. Wire-wound resistor C. Variable resistor D. Carbon composition resistor 84. ECE Board Exam November 1998 If the bands on a resistor are red, red, orange and silver, what is the resistance value? A. 220 ohms 5% B. 223 0hms 10% C. 22,000 ohms 10% D. 2200 ohms 20% 85. ECE Board Exam November 1997 What does the second strip of an electronic resistor color code represent? A. Tolerance B. Second digit of the value C. Temperature D. Multiplier 86. ECE Board Exam November 2000 The energy in an electron that is called the energy of position A. Kinetic energy B. Kinematics C. Electromotive force D. Potential energy 87. ECE Board Exam April 1999 If an electronic resistor does not have the fourth color strip it means it has a tolerance of _____. A. 5% C. 10% B. 20% D. 1% 88. ECE Board Exam April 1998 What happens to the resistance of a conductor wire when its temperature is lowered? A. Decreased C. Zero B. Steady D. Increased 89. ECE Board Exam April 1998 Which of the following does not refer to electric energy? A. Joule C. Volt coulomb B. Watt second D. Volt ampere

90. ECE Board Exam March 1996 Which of the following statement is incorrect? A. open transistor has three (3) terminals B. transistors have three (3) terminals C. typical power rating of carbon-composition resistor ranged 0.001 W to 0.1 W D. potentiometer has three (3) terminals 91. ECE Board Exam November 1997 Term used in electronic measuring device when a metal increases resistance due to heat produced by current flowing through them. A. positive resistance coefficient B. positive temperature coefficient C. negative temperature coefficient D. negative resistance coefficient 92. A 1 km cable consists of 12 identical strands of aluminum each 3 mm in diameter. What is the resistance of the cable? A. 0.34 ohm C. 0.44 ohm B. 0.54 ohm D. 0.24 ohm 93. A piece of wire has a resistance of 0.5 ohm. The length is doubled and the area is increased four times. What is its resistance? A. 0.75 ohm C. 0.25 ohm B. 0.50 ohm D. 1 ohm 94. Copper wire of certain length and resistance is drawn out to four times its length without change in volume. What is the resistance of the bar? A. unchanged C. 16R B. R/16 D. 4R 95. Current is simply _____. A. Flow of electrons B. Flow of protons

C. D.

Radiation Emission

96. The resistance of a coil of wire is 1 kΩ at 20°C. If the coil is immersed into oil, the resistance falls to 880 Ω. If the wire has a temperature coefficient of 0.006 at 20°C, how much is the temperature of the liquid? A. 0°C B. -20°C

C. D.

17.6°C none of these

97. The copper field coils of a motor was measured at 21°C and found to have a resistance of 68 Ω. After the motor has run for a given time, the resistance is found to be 96 Ω. What is the hot temperature of the winding? A. 106.36°C C. 103.66°C B. 166.30°C D. none of these 98. A wire has a resistance of 30 Ω at 20°C. What will its resistance be at 60°C? Assume the temperature coefficient of resistance to be 0.000385 at 20°C. A. 34.26 Ω C. 32.46 Ω B. 36.42 Ω D. none of these

99. Determine the length of a copper wire (ρ = 10.37 ΩCM/ft) where diameter is 0.30 inch and resistance of 0.5 Ω at 20°C. A. 4,339 ft C. 6,125 ft B. 5.225 ft D. none of these 100. An electric water heater has a rating of 1 kW, 230 V. The coil used as the heating element is 10 m long and has a resistivity of 1.724 x 10 -6 ohm-cm. Determine the required diameter of the wire in mils. A. 2.43 mils C. 3.21 mils B. 2.52 mils D. 1.35 mils 101. A certain wire 20 ft long and 100 circular mil area has a resistance of 1.6 . What is its resistivity? A. 10.3 ohm-CM/ft B. 2.2 ohm-CM/ft C. 8 ohm-CM/ft D. 15.2 ohm-CM/ft 102. How many circular mils does a round copper rod of 0.25 inch diameter have? A. 196,000 C. 1,963,500 B. 62,500 D. 49,000 103. A substance whose molecules consist of the same kind of atoms is called ____. A. mixture B. element C. compound D. none of the above 104. The diameter of the atom is about ____. A. 10-10 m C. 10-2 m B. 10-8 m D. 10-15 m 105. The number of compounds available in nature is ____. A. 105 C. 1000 B. 300 D. unlimited 106. The mass of a proton is ____ the mass of an electron. A. equal to B. less than C. about 1837 times D. 200 times 107. The maximum number of electrons that can be accommodated in the last orbit is ____. A. 4 C. 18 B. 8 D. 2 108. The electrons in the last orbit of an atom are called ____ electrons. A. free C. valence B. bound D. thermionic 109. If the number of valence electrons of an atom is less than 4, the substance is usually ____. A. a conductor B. an insulator C. a semiconductor

D.

none of the above

110. If the number of valence electrons of an atom is more than 4, the substance is usually ____. A. a semiconductor B. a conductor C. an insulator D. none of the above 111. If the number of valence electrons of an atom is exactly 4, the substance is usually ____. A. a semiconductor B. an insulator C. a conductor D. a semiconductor 112. The number of valence electrons of an atom is less than 4. The substance will be probably ____. A. a metal B. a non-metal C. an insulator D. a semiconductor 113. One coulomb of charge is equal to the charge on ____ electrons. A. 628 x 1016 C. 62.8 x 1016 16 B. 6.28 x 10 D. 0.628 x 1016 114. One cc of copper has about ____ free electrons at room temperature. A. 200 C. 8.5 x 1022 10 B. 20 x 10 D. 3 x 105 115. Electric current in a wire is the flow of ____. A. free electrons B. bound electrons C. valence electrons D. atoms 116. EMF in a circuit is ____. A. cause current to flow B. maintains potential difference C. increases the circuit resistance D. none of these 117. EMF has the unit of _____. A. power B. energy

C. D.

charge none of these

120. If the length and area of cross-section of a wire are doubled up, then its resistance ____. A. becomes four times B. remains unchanged C. becomes sixteen times D. none of the above 121. A length of wire has a resistance of 6 ohms. The resistance of a wire of the same material three times as long and twice the cross-sectional area will be ____. A. 36 ohms C. 9 ohms B. 12 ohms D. 1 ohm 122. The SI unit of specific resistance is ____. A. mho C. ohm-m2 B. ohm-m D. ohm-cm 123. The specific resistance of a conductor ____ with rise in temperature. A. increases B. decreases C. remains unchanged D. none of the above 124. The SI unit of conductivity is ____. A. ohm-m C. mho-m B. ohm/m D. mho/m 125. The SI unit of conductance is ____. A. mho C. ohm-m B. ohm D. ohm-cm 126. The resistance of a material 2 m long and 2 m2 in cross-sectional area is 1.6 x 10-8 Ω. Its specific resistance will be ____. A. 3.2 x 10-8 ohm-m B. 6.4 x 10-8 ohm-m C. 1.6 x 10-8 ohm-m D. 0.16 x 10-8 ohm-m 127. Conductors have ____ temperature coefficient of resistance. A. positive B. negative C. zero D. none of the above

118. Potential difference has the unit of ____ . A. charge B. power C. energy D. none of the above

128. Semiconductors have ____ temperature coefficient of resistance. A. negative B. positive C. zero D. none of the above

119. The resistance of a material is ____ its area of crosssection. A. directly proportional to B. inversely proportional to C. independent of D. none of the above

129. The value of α (i.e. temperature coefficient of resistance) depends upon A. length of the material B. cross-sectional area of the material C. volume of the material D. nature of the material and temperature

Resistance (Ω)

130. The temperature coefficient of resistance of a conductor ____ with rise in temperature. A. increases B. decreases C. remains unchanged D. none of the above

45°

20 Ω

132. Eureka has ____ temperature resistance. A. positive B. negative C. almost zero D. none of the above

coefficient

of

A. B.

t 40°C Temperature Fig. 1.2 C. 35 ohms D. 50 ohms

70 ohms 40 ohms

137. Referring to Fig. 1.2, the value of α40 will be ____. Resistance (Ω)

131. Insulators have ____ temperature coefficient of resistance. A. zero B. positive C. negative D. none of the above

45°

20 Ω t 40°C Temperature Fig. 1.2

Resistance (Ω)

133. Fig. 1.1 shows the temperature/resistance graph of a conductor. The value of α0 is ____.

40 Ω

A. B.

0.005/°C 0.004/°C

A. B.

50 Ω t 50°C Temperature Fig. 1.1 C. 0.1/°C D. 0.4/°C

Resistance (Ω)

134. Referring to Fig. 1.1, the value of the α50 will be ____.

40 Ω

A. B.

0.005/°C 0.004/°C

50 Ω t 50°C Temperature Fig. 1.1 C. 0.1/°C D. 0.4/°C

135. Referring to Fig. 1.2, the value of α0 is ____. A. 1/30 per °C B. 1/40 per °C C. 1/1200 per °C D. none of the above 136. Referring to Fig. 1.2, the value of R40 will be ____.

1/30 per °C 1/70 per °C

C. D.

1/50 per °C 1/1200 per °C

138. The value of α0 of a conductor is 1/236 per °C. The value of α18 will be ____. A. 1/218 per °C B. 1/272 per °C C. 1/254 per °C D. none of the above 139. The value of α50 of a conductor is 1/230 per °C. The value of α0 will be ____. A. 1/180 per °C B. 1/280 per °C C. 1/250 per °C D. none of the above 140. A good electric conductor is one that A. has low conductance B. is always made of copper wire C. produces a minimum voltage drop D. has few free electrons 141. Two wires A and B have the same cross-section and are made of the same material, RA = 600 Ω and RB = 100 Ω. The number of times A is longer than B is A. 6 C. 4 B. 2 D. 5 142. A coil has a resistance of 100 Ω at 90°C. At 100°C, its resistance is 101 Ω. The temperature coefficient of wire at 90°C is A. 0.01 C. 0.0001 B. 0.1 D. 0.001 143. Which of the following material has nearly zero temperature-coefficient of resistance? A. carbon C. copper B. porcelain D. manganin

144. Which of the following material has a negative temperature coefficient of resistance? A. brass C. aluminum B. copper D. carbon 145. A cylindrical wire 1 m in length, has a resistance of 100 . What would be the resistance of a wire made from the same material both the length and the cross-sectional area are doubled? A. 200 C. 100 B. 400 D. 50 146. Carbon composition resistors are most popular because they A. cost the least B. are smaller C. can withstand overload D. do not produce electric noise 147. A unique feature of a wire-wound resistor is its A. lower power rating C. high stability B. low cost D. small size 148. A coil has a resistance of 100 ohms at 90 °C. At 100°C, its resistance is 101 ohms. What is the temperature coefficient of the wire at 90°C? A. 0.01 C. 0.0001 B. 0.1 D. 0.001 149. What is the unit for charge (Q)? A. Farad C. B. Joule D.

Siemens Coulomb

150. The charge delivered by a constant voltage source is shown. Determine the current supplied by the source at (a) t = 1 s (b) t = 3 s.

A. B.

5 ma, -3.33 ma 5 ma, 3.33 ma

C. D.

–3.33 ma, 5 ma 3.33 ma, 5 ma

Three resistors of 10, 15 and 20 connected in parallel. What is resistance? A. 45 ohms C. B. 17.2 ohms D.

ohms each are the equivalent 0.22 ohm 4.62 ohms

154. REE Board Exam March 1998 Three resistors of 10, 15 and 20 ohms each are connected in parallel. What is the total conductance? A. 0.217 siemens C. 4.52 siemens B. 3.41 siemens D. 0.562 siemens 155. REE Board Exam October 1997 A 5-ohm resistance is connected in parallel with a 10-ohm resistance. Another set, a 6-ohm and an 8ohm resistances are also connected in parallel. The two sets are connected in series. What is the equivalent resistance? A. 6.76 ohm C. 14.4 ohms B. 9.25 ohm D. 21.2 ohms 156. REE Board Exam March 1998 Two resistances of 10 and 15 ohms each respectively are connected in parallel. The two are then connected in series with a 5-ohm resistance. What is the equivalent resistance? A. 11 ohms C. 10 ohms B. 12 ohms D. 9 ohms 157. REE Board Exam October 1997 A 10-ohm and a 20-ohm resistance are connected in parallel. Another resistance of 5-ohm is connected in series with the two. If the supply voltage is 48 volts, what is the current through the 10-ohm resistor? A. 3.21 A C. 4.02 A B. 2.74 A D. 5.72 A 158. REE Board Exam March 1998 Two resistances of 10 and 15 ohms, each respectively are connected in parallel. The two are then connected in series with a 5-ohm resistance. It is then connected across a 12-V battery, what are the current and power? A. 1.2 A, 17.28 W C. 1.09 A, 13.1 W B. 0.96 A, 11.52 W D. 1.5 A, 20.25 W

B. OHM’S LAW AND ELECTRIC CIRCUITS 151. REE Board Exam October 1998 The resistance of 120 meters of wire is 12 ohms. What is its conductance? A. 0.0521 siemens C. 6 siemens B. 0.0833 siemens D. 12 siemens

159. REE Board Exam September 2001 Three resistors 10-Ω, 15-Ω and 20-Ω are connected in series across a 48-V source. What is the voltage across the 15-Ω resistor? A. 20 V C. 24 V B. 16 V D. 12 V

152. EE April 1981, October 1984 Two (2) 115-V incandescent lamps A and B are connected in series across a 230-V source. If lamp A is rated 75 watts and lamp B is rated 50 watts, determine the current drawn by the series connection. A. 0.52 A C. 0.48 A B. 0.64 A D. 0.57 A

160. REE Board Exam September 2001 Three resistors 10-Ω, 15-Ω and 20-Ω are connected in parallel. What is the total resistance? A. 3.56 Ω C. 0.217 Ω B. 4.62 Ω D. 45 Ω

153. REE Board Exam March 1998

161. REE Board Exam September 2000 Two 10-Ω resistances are connected in parallel. The two are then connected in series with a 5-Ω

resistance. It is then connected across a 24-volt battery; find the voltage across the 5-Ω resistor. A. 12 volts C. 9 volts B. 24 volts D. 15 volts 162. REE Board Exam April 1997 A circuit consists of three resistors rated 3-Ω, 4-Ω and 5-Ω connected in parallel. If the circuit is connected to a battery which has an internal resistance of 0.2-Ω, what would be the current through the 4-Ω resistor? A. 2.04 A C. 2.4 A B. 4.8 A D. 3.0 A 163. REE Board Exam September 2000 How many abvolts in 1 volt? A. 108 abvolts C. 1 abvolt B. 10-8 abvolts D. 10 abvolt 164. REE Board Exam September 2003 A total current of 60 A is divided among 3 parallel branches having resistances of 10 Ω, 6 Ω and 12 Ω, respectively. What is the current that flows through the branch with 10 Ω resistance? A. 17.1 A C. 14.3 A B. 28.6 A D. 42.9 A 165. REE Board Exam October 2000 Two 10-ohm parallel resistors are connected in series with a 5-ohm resistor. The combination is then connected across a 24 volts battery. Find the voltage drop across the 5-ohm resistor. A. 6 V C. 12 V B. 18 V D. 20 V 166. ECE Board Exam November 1998 The theory of Ohm’s law is applied in a _____ circuit. A. linear C. trivalent B. exponential D. unilateral 167. ECE Board Exam April 2000 Refers to the most important components in controlling flow of electrons A. voltage, electromotive force and current B. reactance, current and resistance C. conductance, resistance and reactance D. voltage, resistance and current 168. ECE Board Exam November 1999 Which of the following is not a valid expression of ohm’s law? A. E = IR C. R = E/I B. R = PI D. I = E/R 169. ECE Board Exam November 2000 A simple electronic equipment which takes a 2 amperes current from a power source has a total load resistance of 100 ohms. How much power does it use? A. 200 watts C. 400 watts B. 100 watts D. 50 watts 170. ECE Board Exam November 1996

What do you expect when you use the two 20 kohms, 1 watt resistor in parallel instead of one 10 kohms, 1 watt? A. Provide lighter current B. Provide wider tolerance C. Provide more power D. Provide less power 171. ECE Board Exam November 1999 The total resistance of a two similar wire conductors connected in parallel is ______ A. same resistance of one wire B. double the resistance of one wire C. one half the resistance of one wire D. resistance of one wire multiplied by 4 172. ECE Board Exam March 1996 When you increase the resistance in a circuit, the flow of electrons will ______. A. be constant C. be stopped B. flow faster D. be decreased 173. ECE Board Exam April 2001 Which of the following allows more current if applied to the same voltage? A. 0.002 siemen C. 0.004 siemen B. 25 ohms D. 2.5 ohms 174. ECE Board Exam April 1998 Ohm’s law refers to _____. A. power is directly proportional to both voltage squared and the resistance B. power is directly proportional to the resistance and inversely as the current squared C. current varies directly as the voltage and inversely as the resistance D. current is directly proportional to both voltage and resistance 175. ECE Board Exam November 2000 A circuit which a break exists in the complete conduction pathway A. Open circuit C. Close circuit B. Short circuit D. Circuit 176. ECE Board Exam November 1997 How much is the equivalent power in watts can a 3 horse power provide? A. 3000 watts C. 1492 watts B. 248.66 watts D. 2238 watts 177. ECE Board Exam March 1996 The current needed to operate a soldering iron which has a rating of 600 watts at 110 volts is A. 18,200 A C. 66,000 A B. 0.182 A D. 5.455 A

178. ECE Board Exam November 1997

Find the power across the resistor of 5 ohms delivered from a battery of an internal resistance of 3 ohms and a constant emf of 4 volts. A. 120 watts C. 60 watts B. 100 watts D. 1.25 watts 179. ECE Board Exam April 2000 A series circuit in which desired portions of the source voltage may be tapped off for use equipment. A. Voltage trap B. Voltage selector C. Voltage divider D. Dividing network 180. ECE Board Exam April 1998 An electronic device draws 300 watts from its 24 volt power source. Find effective resistance. A. 1.25 Ω C. 19.20 Ω B. 1.92 Ω D. 12.50 Ω 181. ECE Board Exam November 1997 How much power does an electronic equipment consume, assuming a 5.50 amperes current flowing and a 120 volts power source? A. 125.5 watts C. 660 watts B. 66 watts D. 60 watts

187. ECE Board Exam November 1999 A condition in which the heat in of around the circuit increases beyond or to a higher than normal level. A. Excessive heat condition B. Open condition C. Direct short D. Grounded 188. ECE Board Exam November 1999 A 33 kilo ohms resistor is connected in a series parallel combination made up of a 56 kilo ohm resistor and a 7.8 kilo ohm resistor. What is the total combined resistance of these three resistors? A. 39067 ohms C. 63769 ohms B. 49069 ohms D. 95800 ohms 189. ECE Board Exam April 2001 If 3,300 ohms resistor and a 22,000 ohms resistor are connected in series, what is the total resistance? A. 18,700 ohms C. 5,500 ohms B. 25,300 ohms D. 2,870 ohms 190. ECE Board Exam November 2000 A device that draws current A. Source C. Load B. No load D. Shunt

182. ECE Board Exam March 1996 What type of circuit whose parameters are constant which do not change with voltage or current? A. Tuned circuit C. Reactive circuit B. Linear circuit D. Lumped circuit

191. ECE Board Exam April 1998 With the same voltage applied which of the following allows more current? A. 25 ohms C. 2.5 ohms B. 250 ohms D. 0.25 ohms

183. ECE Board Exam April 2000 If three circuits, each with a value of 560 ohms are connected in parallel, what is the total resistance of the combination? A. 1680 ohms C. 18567 ohms B. 560 ohms D. 187 0hms

192. ECE Board Exam April 1998 If 12 V are applied to a circuit that consumes 78 W, what is the current flow through the circuits? A. 6.5 A C. 0.15 A B. 936 A D. 9.36 A

184. ECE Board Exam November 1997 Other factors remaining constant, what would be the effect on the current flow in a given circuit if the applied potential were doubled? A. It would double B. It would increase 4 times C. It would remain the same D. It would be decrease by ½ 185. ECE Board Exam April 1999 Find used power of a circuit whose power source supplies 20 volts and a load resistance of 200 ohms. A. 1 watt C. 10 watts B. 4 kilowatts D. 2 watts 186. ECE Board Exam April 1998 When resistors are connected in series, what happens? A. Nothing B. The tolerance is decreased C. The effective resistance is decreased D. The effective resistance is increased

193. ECE Board Exam April 1998 Find the current that flows through the filament of a 400 watt flat iron connected to a 220 volt power line. A. 50 mA C. 5 mA B. 500 mA D. 5 A 194. Four equal resistances are connected in parallel across a certain supply producing P power. How much power will be produced if the resistances are now connected in series across the same supply? A. 16P C. 4P B. P/16 D. P/4 195. A resistor R is connected across a 120 V supply. A voltmeter of 10,000 ohms resistance is connected between the center of the resistor and one side of the supply and reads 40 V. What is the value of the resistance R? A. 10,000  C. 30,000  B. 20,000  D. 15,000  196. A 240 V motor requiring 2,000 W is located 1 km from a power source. What diameter of copper wire is to be used if the power loss is to be kept 5%?

A. B.

0.49 cm 0.54 cm

C. D.

0.39 cm 0.35 cm

197. Three resistors of 10, 12 and “x” ohms, respectively are connected in parallel across a constant current source of 8 A. Determine “x” if this resistor draws 2.5 A. A. 10 Ω C. 13 Ω B. 12 Ω D. 11 Ω 198. An arc lamp takes 10 A at 50 volts. A resistance R is to be place in series so that the lamp my burn correctly from a 110 V supply. Find the power wasted in this resistor. A. 800 watts C. 700 watts B. 600 watts D. 900 watts 199. A 20  and 10  resistors are connected in parallel and a 5  resistor is connected in series with the parallel combination. The circuit is connected across a 48 V source with an internal resistance of 0.2 . Calculate the current through the 5  resistor. A. 5.57 amperes C. 3.58 amperes B. 4.04 amperes D. 7.63 amperes

A. B. C. D.

resistance inductance capacitance both inductance and capacitance

207. The purpose of load in an electric circuit is to ____. A. increase the circuit current B. utilize electrical energy C. decrease the circuit current D. none of the above 208. Electrical appliances are not connected in series because ____ A. series circuit is complicated B. appliances have different current rating C. power loss is more D. none of the above 209. Electrical appliances are connected in parallel because it ____ A. is a simple circuit B. draws less current C. results in reduce in power loss D. makes the operation of appliances independent of each other

200. A variable resistor R is connected in parallel with a fixed resistor of 1.25 ohms. The combination is then connected across a 12 V battery with internal resistance of 0.25 Ω. Solve for the maximum power that can delivered to R. A. 130.20 W C. 120.21 W B. 115.52 W D. 142.42 W

210. Inductance and capacitance are not relevant in a d.c. circuit because ____ A. frequency of d.c. is zero B. it is a simple circuit C. they do not exist in a d.c. circuit D. none of the above

201. The hot resistance of an incandescent lamp is 10 ohms and the rated voltage is 50 V. Find the series resistance required to operate the lamp from an 80 V supply. A. 8  C. 6  B. 4  D. 10 

211. The hot resistance of a 100 watt, 250 V incandescent lamp would be A. 2.5 ohms B. 625 ohms C. 25 ohms D. none of the above

202. Ohm’s law is not applicable to A. copper B. silver C. silicon carbide D. aluminum 203. The practical unit of electrical energy is A. watt B. kilowatt C. kilowatt-hour D. megawatt 204. A 100 watt lamp working for 20 hours will consume ____ units. A. 200 C. 2 B. 20 D. 5

212. The voltage drop across 14.5 ohm resistor in Fig. 2.1 is ____. 14.5 Ω +

200 V

60 Ω -

Fig. 2.1

A. B.

29 V 14 V

C. D.

30.5 V 18 V

213. The circuit shown in Fig. 2.1 is called a series circuit because ____ 14.5 Ω

205. The hot resistance of an incandescent lamp is about ____ its cold resistance. A. 10 times C. 100 times B. 2 times D. 50 times 206. A d.c. circuit usually has ____ as the load.

25.5 Ω

25.5 Ω +

200 V

60 Ω -

Fig. 2.1

A. B.

it contains a few resistances it carries the same current throughout the circuit

C. D.

it is a simple circuit none of the above

2.5 Ω 7A 4.5 Ω

214. Referring to Fig. 2.2, the total circuit resistance will be ____ 100 W, 200 V 40 W, 200 V

Fig. 2.4

A. B. Lamp A +

Lamp B -

200 V

3A 4.5 A

2.5 Ω 7A

1000 ohms 400 ohms

C. D.

215. In Fig. 2.2 ____ 100 W, 200 V

1400 ohms 135 ohms

40 W, 200 V

Lamp B 200 V

-

Fig. 2.2

A. B. C. D.

4.5 Ω Fig. 2.4

Lamp A +

the lamp A will be brighter than lamp B the lamp B will be brighter than lamp A the two lamps will be equally bright none of the above

216. When a number of resistances are connected in parallel, the total resistance is ____ A. less than the smaller resistance B. greater than the smaller resistance C. between the smaller and greatest resistance D. none of the above

A. B.

3.5 A 3A

218. The value of R that will give a total resistance of 1.5 ohms in Fig. 2.3 is ____ 3Ω

2A 2.5 A

222. Two incandescent lamps of 100 W, 200 V are in parallel across 200 V supply. The total resistance will be ____. A. 800 ohms C. 400 ohms B. 200 ohms D. 600 ohms 223. The resistance across the terminals AB of the circuit shown in Fig. 2.5 is ____

A 18 Ω

12 Ω 6Ω

B

C

Fig. 2.5 A. B.

36 ohms 18 ohms

C. D.

9 ohms 15 ohms

224. If a d.c. supply of 180 V is connected across terminals AB in Fig. 2.5, then current in 6 ohm resistor will be ____.

R

A

Fig. 2.3 4 ohms 6 ohms

C. D.

221. If 18 resistances, each of value 36 ohms, are connected in parallel, then the total resistance is ____ A. 2 ohms B. 54 ohms C. 36 ohms D. none of the above

217. Two resistances of 6 ohms and 3 ohms are connected in parallel. The total resistance is ____ A. 9 ohms C. 0.5 ohm B. 18 ohms D. 2 ohms

A. B.

2.5 A 2A

220. The current in 4.5 ohms resistor in Fig. 1.4 will be ____.

Fig. 2.2

A. B.

C. D.

C. D.

3 ohms 9 ohms

18 Ω

12 Ω 6Ω

B

219. The current in 2.5 ohm resistor in Fig. 2.4 will be ____

C

Fig. 2.5 A. B.

10 A 5A

C. D.

12 A 6A

225. The resistance across terminals AC in Fig. 2.5 is ____

230. If 10 ohms resistance is removed in Fig. 2.7, then total conductance of the circuit will be ____

A 18 Ω

12 Ω 6Ω

2Ω

1Ω

C

B

10 Ω

Fig. 2.5 A. B.

36 ohms 9 ohms

C. D.

18 ohms 8 ohms

226. The resistance across terminals AB of the circuit shown in Fig. 2.6 is ____ 5Ω 2Ω A

3 mhos 6 mhos

2 mhos 1.5 mhos

231. The voltage across the parallel circuit shown in Fig. 2.8 is ____

B

10 Ω

2.5 Ω

15 A

4Ω

6Ω

C. D.

2Ω

8Ω

Fig. 2.7

A. B.

Fig. 2.6

A. B.

4 ohms 18 ohms

C. D.

34 ohms 8 ohms

15 V 10 V

C. D.

30 V 12. 5 V

232. The current in 10 ohms resistor in Fig. 2.8 is ____

10 Ω

2.5 Ω

15 A

4Ω

6Ω

8Ω

A. B.

2Ω

227. If a battery of 24 V is applied across terminals AB of the circuit shown in Fig. 2.6, then current in 2 ohm resistor will be ____ 5Ω 2Ω A

Fig. 2.8

B Fig. 2.8

Fig. 2.6

A. B.

3A 6A

C. D.

2.5 A 1.5 A

228. If a battery of 24 V is applied across terminals AB in Fig. 2.6, then power loss in 5 ohms resistor will be ____ 5Ω 2Ω A

C. D.

90 W 24 W

229. The total conductance of the circuit shown in Fig. 2.7 is ____

2Ω

2Ω 1

4Ω

2

12 ohms 2.67 ohms

C. D.

2Ω

2 ohms 64 ohms

234. If a battery of 12 V is applied across terminals 1 and 2 of Fig. 1.9, then current through 4 ohms resistor will be ____ 2Ω

2Ω 1Ω

1.5 A 3.5 A

233. The total resistance between terminals 1 and 2 of the circuit shown in Fig. 2.9 is ____

A. B.

Fig. 2.6

180 W 45 W

C. D.

Fig. 2.9

B

A. B.

3A 2.5 A

4Ω

6Ω

8Ω

A. B.

1

10 Ω

4Ω

2

Fig. 1.9 Fig. 2.7

A. B.

13 mhos 1.6 mhos

C. D.

6 mhos 2.5 mhos

A. B.

1.5 A 3A

C. D.

2A 2.5 A

235. The resistance between terminals 1 and 2 of Fig. 1.10 is ____

2Ω

14

Fig. 1.10

A. B.

12 ohms 8 ohms

F

C. D.

16 ohms 3 ohms

236. The resistance between terminals 1 and 2 in Fig. 1.11 is ____ 1Ω

Ω

1

E

A. B. C. D.

9 ohms 18 ohms 10 ohms none of the above

1Ω

A

13 Ω

11 Ω

B

72

6Ω

14

Ω

44 V

C. D.

1 ohm 4 ohms

237. If a battery of 6 V is applied across terminals 1 and 2 in Fig. 1.11, then current in the horizontal 2 ohm resistor will be ____ 1Ω 2 Ω

1Ω

18 Ω

Ω

2 ohms 1.5 ohms

1

C

2

2Ω Fig. 1.11

A. B.

D

9Ω

Fig. 1.13

241. Referring to Fig. 1.13, the resistance across terminals AF is ____

2

1Ω

6Ω

Ω

44 V

C

18 Ω

Ω

2Ω 2

6Ω

11 Ω

B

72

2Ω 1

13 Ω

A

1Ω 2

2Ω

F

E

D

9Ω

Fig. 1.13

A. B. C. D.

20.5 ohms 18 ohms 11 ohms none of the above

242. Referring to Fig. 1.13, the current in 18 ohms resistor will be ___ A

13 Ω

11 Ω

B

C

Fig. 1.11

238. The resistance across terminals 1 and 2 in Fig. 1.12 is ____

6 ohms 12 ohms

Ω

A. B.

2

2Ω

C. D.

18 ohms 24 ohms

F

E

A. B. C. D.

2A 1.5 A 1A none of the above

243. Referring to Fig. 1.13, the power loss in 11 ohms will be ____ A

13 Ω

C

18 Ω

Ω

44 V

11 Ω

B

F

E Fig. 1.13

240. Referring to Fig. 1.13, the resistance across terminals BE is ____

D

9Ω

Fig. 1.13

72

239. Two equal resistances are connected in series across a certain supply. If the resistances are now connected in parallel across the same supply, the power produced will be ____ that of series connection. A. two times C. one-half B. four times D. one-fourth

6Ω

6Ω

14

2

1Ω 1

1Ω

18 Ω

Ω

44 V

14

3A 0.5 A

Ω

C. D.

Ω

1A 2A

72

A. B.

A. B. C. D.

11 W 24 W 16 W none of the above

9Ω

D

244. If in Fig. 1.14, switches S1 and S2 are closed, then total circuit resistance is ____ 100 W, 200 V L2

S1

40 W, 200 V L1

S2

Fig. 1.14

400 ohms 1200 ohms

C. D.

1000 ohms 2400 ohms

245. If switch S1 is open and switch S2 is closed in Fig. 1.14, then circuit resistance will be ____

S2

Fig. 1.14

A. B. C. D.

lamp L1 will burn out lamp L2 will burn out both lamps L2 and L3 will burn out all the lamps will be safe

249. If in Fig. 1.1, resistor R2 becomes open-circuited, the reading of the voltmeter will become V

L3

R1

R2

R3

R4

20 Ω

20 Ω

20 Ω

20 Ω

100 W, 200 V + 200 V -

200 V

Fig. 1.14

A. B.

1200 ohms 1000 ohms

C. D.

1400 ohms 2400 ohms

246. If in Fig. 1.14, both switches S1 and S2 are closed, then ____ 100 W, 200 V L2

S1

40 W, 200 V L1

L3

100 W, 200 V + 200 V -

100 W, 200 V L2

S1

40 W, 200 V L1

100 W, 200 V L2

S2

L3

100 W, 200 V + 200 V -

A. B.

S1

40 W, 200 V L1

Figure 1.1 A. B.

zero 150 V

C. D.

50 V 200 V

250. Whatever the battery voltage in Fig. 1.2, it is certain that smallest current will flow in the resistance of ____ ohm. 300 Ω

S2

L3

500 Ω 100 W, 200 V + 200 V -

100 Ω 200 Ω

Fig. 1.14

A. B. C. D.

L1 will be brighter than L2 or L3 L1 will be dimmer than L2 or L3 L1 will be as bright as L2 or L3 none of the above

247. If in Fig. 1.14 switches S1 and S2 are open, then lamp L1 will give output ____ 40 W, 200 V L1

S1

100 W, 200 V L2

S2

L3

100 W, 200 V + 200 V Fig. 1.14

A. B. C. D.

less than 40 W more than 40 W equal to 40 W none of the above

248. If in Fig. 1.14 switches S1 and S2 are closed and the supply voltage is increased to 400 V, then ____

Figure 1.2 A. B.

300 500

C. D.

200 100

251. Which of the following statement is TRUE both for a series and parallel d.c circuit? A. powers are additive B. voltages are additive C. current additive D. elements have individual currents 252. A 100-W, 110-V and a 50-W lamp are connected in series across a 220-V dc source. If the resistances of the two lamps are assumed to remain constant, the voltage across the 100-W lamp is ____ volt. A. 110 C. 146.7 B. 73.3 D. 220

253. In the parallel circuit of Fig.1.3, the value of V0 is ____ volt.

R3

R1

2Ω VO

E

R2

2Ω 12 V

A. B.

12 V

Figure 1.3

12 24

C. D.

A. B. C. D. 0 -12

254. In the series circuit of Fig 1.4, the value of V0 is ____ volt. 2Ω

Figure 1.7 E and R1 form a series circuit R1 is in series with R3 R1 is in series with R2 there is no series circuit

258. Which of the following statements is correct concerning the Fig. 1.8? R2

VO

R1 12 V

Figure 1.4 A. B.

R3

E

2Ω

12 -12

C. D.

0 6

255. In Fig 1.5, there is a drop of 20 V on each resistor. The potential of point A would be ____ volt. A

B

A. B. C. D.

Figure 1.8 R2 and R3 form a series of path E is in series with R1 R1 is in parallel in R3 R1, R2 and R3 form a series of circuit

259. What is the equivalent resistance in ohms between points A and B of Fig. 1.9? All resistances are in ohms A

80 V

12 Ω

G

6Ω

D

C

4Ω B

Figure 1.5 A. B.

+80 -40

C. D.

+40 -80

256. From the voltmeter reading of Fig. 1.6, is it obvious that 4Ω

24 V 3 Ω

A. B. C. D.

6Ω

Figure 1.6 the 3  resistor is short circuited the 6  resistor is short circuited nothing is wrong with the circuit the 3  resistor is open-circuited

257. With reference to Fig 1.7, which of the following statement is true?

A. B.

12 14.4

Figure 1.9

C. D.

22 2

260. What do you call a resistor that does not obey Ohm’s Law? A. Potentiometer B. Carbon-Film Resistor C. Wire-Wound Type D. Non-linear Resistor 261. A 100 W, 110 V and 50 W, 110 V lamps are connected in series across a 220 V DC source. If the resistances of the two lamps are assumed to remain constant, the voltage across the 100 W lamp is _____ volt? A. 110 V C. 146.7 V B. 73.3 V D. 220 V 262. A potential divider of resistance of 50 ohms is connected across a 100 V DC source. A load resistance of 10 ohms is connected across a tap in the potential divider and the negative terminal of the

source. If a current of 4 A flows towards the load, what is the current supplied by the source? A. 5.32 A C. 5.21 A B. 5.05 A D. 5.48 A 263. Two resistors A and B made of different materials have temperature coefficients of resistance at 20C of 0.004 and 0.006 respectively. When connected across a voltage source at 20C, they draw current equally. What percentage of the total current at 100C does resistor A carry? A. 47.14% C. 61.34% B. 52.86% D. 38.66% 264. A conductor has a resistance 20C, the resistance has Calculate the temperature conductor at 20C. A. 1/300 /°C B. 1/400 /°C

of 7 ohms at 0C. At become 7.5 ohms. coefficient of the C. D.

1/500 /°C 1/600 /°C

265. Which of the following is a non-linear element? A. diode B. heater coil C. transistor D. electric arc with unlike electrode C. ELECTRICAL AND HEAT ENERGY 266. EE Board Exam April 1992 An electric kettle was marked 500 W, 230 V found to take 15 minutes to bring 1 kilogram of water at 15°C to boiling point. Determine the heat efficiency of the kettle. A. 79.1% C. 72.4% B. 75.3% D. 74.8% 267. REE Board Exam October 1997 A process equipment contains 100 gallons of water at 25°C. It is required to bring it to boiling in 10 minutes. The heat loss is estimated to be 5%. What is the kW rating of the heater? A. 125 kW C. 50.5 kW B. 252 kW D. 207 kW 268. EE October 1989 A total of 0.8 kg of water at 20°C is placed in a 1-kW electric kettle. How long a time in minute is needed to raise the temperature of the water to 100°C? A. 4.46 min C. 5.34 min B. 5.32 min D. 4,.56 min 269. REE October 1998 How many calories does an electric heater of 100 watts generate per second? A. 10 C. 23.88 B. 1000 D. 42.25 270. REE Board Exam October 1997 The electric energy required to raise the temperature of water in a pool is 1000 kWh. If the heat losses are 25%, the heating energy required will be ____. A. 1111 kWh C. 1750 kWh B. 1266 kWh D. 1333 kWh

271. EE Board Exam April 1992 An electric heater carries 12 A at 110 V, is submerged in 22.5 lbs of water for 30 minutes. What will be the final temperature of the water if its initial temperature is 35°F? A. 135.43°F C. 133.56°F B. 125.42°F D. 128.33°F 272. EE Board Exam October 1990 In an electric heater the inlet temperature is 15°C. Water is flowing at the rate of 300 grams per minute. The voltmeter measuring voltage across the heating element reads 120 volts and an ammeter measuring current taken reads 10 amperes. When steady state is finally reached, what is the final reading of the outlet thermometer? A. 57.6°C C. 72.6°C B. 68.4°C D. 42.6°C 273. EE Board Exam October 1991 Four cubic meters of water is to be heated by means of four 1.5 kW, 230-V immersion heating elements. Assuming the efficiency of the heater as 90%, determine the time required in boiling the water if the initial temperature is 20°C and if all four elements are connected in parallel. A. 71 hrs C. 69 hrs B. 63 hrs D. 66 hrs 274. EE Board Exam October 1991 Four cubic meters of water is to be heated by means of four 1.5 kW, 230-V immersion heating elements. Assuming the efficiency of the heater as 90%, determine the time required in boiling the water if the initial temperature is 20°C and if the elements are connected two in series in parallel with two in series. A. 275.6 hrs C. 252.2 hrs B. 295.3 hrs D. 264.4 hrs 275. REE Board Exam September 2001 How many joules per second are then in 10 watts? A. 10 C. 20 B. 5 D. 24.5 276. REE Board Exam September 2001 1013 ergs/sec is equal to how many kilowatts? A. 1,000 C. 100 B. 250 D. 10 277. REE Board Exam September 2000 What is 1 kW-hr in BTU? A. 4,186 C. 746 B. 3,413 D. 1,000 278. REE Board Exam October 1998 What is the work in ergs needed to raise a 10 g weight 100 m up? A. 4.9 x 105 C. 98 x 107 B. 9.8 x 107 D. 1.96 x 107 279. REE Board Exam October 1999

The quantity of heat required to raise the temperature of water by 1°C. A. energy C. calorie B. specific heat D. BTU 280. REE Board Exam October 1999 When heat is transferred into any other form of energy or when other forms of energy are converted into heat, the total amount of energy is constant. This is known as A. First law of thermodynamics B. Boyle’s law C. Specific heat D. Isothermal expansion 281. REE Board Exam September 2002 What is 1012 ergs/sec in kW? A. 100 kW C. 10 kW B. 1,000 kW D. 10,000 kW 282. REE Board Exam October 2000 An electric heater is used to heat up 600 grams of water. It takes 14 minutes to raise the temperature of water by 40°C. If the supply voltage is 220 volts, what is the power rating of the heater neglecting heat losses? A. 180 W C. 200 W B. 120 W D. 60 W 283. REE Board Exam April 2001 A 100 liter of water is heated from 20°C to 40°C. How many kWHR of electricity is needed assuming no heat loss? A. 4.2 C. 5.6 B. 2.3 D. 3.7 284. REE Board Exam April 2002 Ten (10) kW is equal to ____ gram-cal/sec. A. 156 C. 2,388 B. 436 D. 425 285. ECE Board Exam November 1995 Two heaters A and B are in parallel across supply voltage V. Heater A produces 500 kcal in 20 minutes and B produces 1000 kcal in 10 minutes. The resistance of A is 10 ohms. What is the resistance of B, if the same heaters are connected in series voltage V? A. 4.5 ohms C. 4.5 ohms B. 2.5 ohms D. 0.14 ohm 286. In the SI system of units, the unit of force is A. kg-wt C. Joule B. Newton D. N-m 287. The basic unit of electric charge is A. ampere-hour C. coulomb B. watt-hour D. farad 288. The SI unit of energy is A. Joule B. kWh

C. D.

kcal m-kg

289. The SI unit of energy is A. Joule B. kWh

C. D.

kcal m-kg

290. Two heating elements, each of 230-V, 3.5 kW rating are first joined in parallel and then in series to heat same amount of water through the same range of temperature. The ratio of the time taken in the two cases would be A. 1:2 C. 1:4 B. 2:1 D. 4:1 291. If a 220 V heater is used on 110 V supply, heat produced by it will be ____ as much A. one-half C. one-fourth B. twice D. four times 292. For a given line voltage, four heating coils will produce maximum heat when connected A. all in parallel B. all in series C. with two parallel pairs in series D. one pair in parallel with the other two in series 293. The electric energy required to raise the temperature of a given amount of water is 1000 kWh. If heat losses are 25%, the total heating energy required is ____ kWh. A. 1500 C. 1333 B. 1250 D. 1000 294. One kWh of energy equals nearly A. 1000 W C. B. 860 kcal D.

4186 J 735.5 W

295. A force of 10,000 N accelerates a body to velocity 0.1 km/s. The power developed is ____ kW. A. 1,000,000 C. 3600 B. 36,000 D. 1000 296. A 100 W light bulb burns on an average of 10 hours a day for one week. The weekly consumption of energy will be ____ unit/s. A. 7 C. 0.7 B. 70 D. 0.07 297. Two heaters, rated at 1000 W, 250 volts each, are connected in series across a 250 volt, 50 Hz A.C. mains. The total power drawn from the supply would be ____ watt. A. 1000 C. 250 B. 500 D. 2000 298. One watt is equal to ____. A. 4.19 cal/sec B. 778 BTU/sec

C. D.

107 ergs/sec 10-7 ergs/sec

299. The current in an electric lamp is 5 amperes. What quantity of electricity flows toward the filament in 6 minutes? A. 30 C C. 72 C B. 3600 C D. 1800 C

300. An electric heater is rated at 120 volts, 1000 watts and is used to boil water. Calculate the time in minutes to raise the temperature of 1 liter of water from 15°C to boiling. The heater has an over-all efficiency of 92%. A. 6.4 minutes C. 4.4 minutes B. 5.4 minutes D. 3.4 minutes 301. For a given line voltage, four heating coils will produce maximum heat when connected A. all in parallel B. all in series C. with two parallel pairs in series D. one pair in parallel with the other two in series 302. Four heaters having the same voltage rating will produce maximum heat if connected in A. Series C. Series-Parallel B. Parallel D. Parallel-Series 303. 1000 kW is equal to how many is ergs/sec. A. 2 x 1013 C. 1 x 1013 16 B. 1 x 10 D. 2 x 1010 304. When current flows through heater coil, it glows but supply wiring does not glow because A. supply wiring is covered with insulation wiring B. current through supply line flows at slower speed C. supply wires are made of superior material D. resistance of heater coil is more than that of supply wire D. ELECTRIC CELLS 305. REE Board Exam October 1997 A load of 10 ohms was connected to a 12-volt battery. The current drawn was 1.18 amperes. What is the internal resistance of the battery? A. 0.35 ohm C. 0.25 ohm B. 0.20 ohm D. 0.30 ohm 306. REE Board Exam April 1997 The electromotive force of a standard cell is measured with a potentiometer that gives a reading of 1.3562 V. When a 1.0 megaohm resistor is connected across the standard cell terminals, the potentiometer reading drops to 1.3560 V, what is the internal resistance of the standard cell? A. 174.5 ohms C. 147.5 ohms B. 145.7 ohms D. 157.4 ohms 307. REE Board Exam April 1997 If a resistor rated at 5 watts and 6 volts are connected across a battery with an open circuit voltage of 6 volts. What is the internal resistance of the battery if the resulting current is 0.8 A? A. 0.30 ohm C. 0.23 ohm B. 0.26 ohm D. 0.03 ohm 308. REE Board Exam October 1998 A 12 V battery of 0.05-ohm resistance and another battery of 12 V and 0.075 ohm resistance supply

power to a 2-ohm resistor. What is the current through the load? A. 5.85 A C. 5.72 A B. 5.63 A D. 5.91 A 309. REE Board Exam October 1996 The lead batteries “A” and “B” are connected in parallel. “A” has an open circuit voltage of 12 V and an internal resistance of 0.2 ohm. Battery “B” has an open circuit voltage of 12.2 V and an internal resistance of 0.3 ohm. The two batteries together deliver power to a 0.5 ohm power resistor. Neglecting effects of temperature, how much current is contributed by battery “A”? A. 29.62 A C. 12.85 A B. 16.00 A D. 25.24 A 310. EE Board Exam October 1981 A charger, a battery and a load are connected in parallel. The voltage across the charger is 12.5 volts and the battery has an emf of 12 volts and internal resistance of 0.1 ohm. The load consists of a 2 ohms resistor. Find the current through the charger. A. 6.61 A C. 6.42 A B. 6.25 A D. 6.50 A 311. REE Board Exam October 1996 A lead storage battery is rated at 12 volts. If the internal resistance is 0.01 ohm, what is the maximum power that can be delivered to the load? A. 1,200 W C. 7,200 W B. 3,600 W D. 1,800 W 312. EE Board Exam April 1995 A 120-V battery having an internal resistance of 0.5 ohm is connected through a line resistance of 0.5 ohms to a variable load resistor. What maximum power will the battery deliver to the load resistor? A. 36 watts C. 630 watts B. 63 watts D. 360 watts 313. REE Board Exam April 2002 A 12 volts battery has a 50 ampere-hour capacity. The internal resistance is 0.1 ohm. A 5 ohm load is connected for 5 hours. How many ampere-hours are still left? A. 28.51 C. 38.23 B. 41.24 D. 35.92 314. REE Board Exam April 2002 Two-24 volt battery supply power to a 20 ohm load. One battery has 0.2 ohm internal resistance while the other has 0.4 ohm. What power does the load draws? A. 28.4 W C. 30.8 W B. 22.2 W D. 18.6 W 315. ECE Board Exam March 1996 Which statement is not true? A. Secondary cell can be recharged B. The internal resistance of a cell limits the amount of output current

C.

The negative terminal of a chemical cell has a charge of excess electrons Two electrodes of the same metal provide the highest voltage output

_____ is the specific gravity reading for a good lead acid cell. A. 1170 C. 1070 B. 1270 D. 1370

316. ECE Board Exam November 2001 In the operation of dry cell we normally refer to the supply of current load resistance where its current neutralizes the separated charges at the electrodes. A. Aligning the cells B. Charging the cells C. Discharging the cells D. Polarizing the cells

325. ECE Board Exam November 1998 Refers to a power source or cell that is not rechargeable? A. Secondary C. Storage B. Primary D. Battery

D.

317. ECE Board Exam November 2000 Refers to a power source or cell which can be rechargeable A. Battery C. Primary B. Secondary D. Storage 318. ECE Board Exam November 2001 In the operation of dry cell we normally refer to the supply of current load resistance where its current neutralizes the separated charge s at the electrodes. A. Aligning the cells B. Charging the cells C. Discharging the cells D. Polarizing the cells 319. ECE Board Exam November 2000 The part of the cell of the solution that acts upon the electrodes providing a path for electron flow A. Container C. Sealing way B. Electrolyte D. Electrolysis 320. ECE Board Exam April 1999 Type of cell used mostly for emergency equipment. It is light, small, and has a large capacity of power for its size. A. Ni-Cd cell C. Silver-zinc cell B. Silver-cadmium cell D. Mercury cell 321. ECE Board Exam March 1996 The purpose of cells connected in parallel is to_____. A. increase internal resistance B. increase in voltage output C. decrease current capacity D. increase in current capacity 322. ECE Board Exam November 1995 Find the output of a four (4) lead acid cells. A. 3.2 V C. 5.8 V B. 8.4 V D. 1.6 V 323. ECE Board Exam November 1997 How many silver zinc cells in series are needed for a 9V battery? A. 9 C. 3 B. 6 D. 7 324. ECE Board Exam November 1995

326. ECE Board Exam April 1998 Which of the following is not a primary type cell? A. Zinc-chloride C. Silver oxide B. Silver-zinc D. Carbon zinc 327. ECE Board Exam November 1997 A battery should not be charged or discharged at a high current in order to avoid this defect. A. Corrosion C. Buckling B. Sedimentation D. Sulphation 328. ECE Board Exam April 2001 It is a cell in which the chemical action finally destroys one of the electrons electrodes, usually the negative and cannot be recharged. A. Dry cell C. Wet cell B. Secondary cell D. Primary cell 329. ECE Board Exam November 2001 Which of the following statements is not true? A. Output of solar cell is normally 0.5 V B. Edison cell is storage type C. The Ni-Cd cell is primary type D. Primary cells can be charged 330. ECE Board Exam April 2001 Which of the following statements is not true? A. A primary cell has irreversible chemical reaction B. A carbon zinc cell has unlimited shelf life C. A storage cell has irreversible chemical reaction D. A lead acid cell can be recharged 331. ECE Board Exam November 1999 A device that transforms chemical energy into electrical energy A. Battery B. Cell C. Primary battery D. Secondary battery 332. ECE Board Exam April 1999 What is the effect of connecting battery cells in parallel? A. Current decreases B. Voltage increases C. Voltage decreases D. Current increases 333. ECE Board Exam November 1997 Determine how long a battery will last whose rating is 100 Ah, 24 volts and will run a 300 watts electronic equipment and a 50 watts light.

A. B.

6.85 hours 50.05 hours

C. D.

26.65 hours 12.00 hours

334. ECE Board Exam April 2001 The process of reversing the current flow through the battery to store the battery to its original condition A. Electrolysis C. Reverse flow B. Ionization D. Battery charge 335. ECE Board Exam November 2000 The type of cell commonly referred to as “flashlight battery” A. Nickel-cadmium battery C. Dry cell B. Mercury cell D. Lead acid cell 336. ECE Board Exam November 1998 How does a battery behave whose cells are connected in series? A. Increase current supply B. Reduces total voltage C. Increases voltage supply D. Reduces internal resistance 337. ECE Board Exam April 1998 Another very useful cell to solar cells however the junction is bombarded by beta particles from radioactive materials A. Alkaline cells C. Selenium cells B. Nucleus cells D. Lithium cells 338. ECE Board Exam November 2001 The continuation of current flow within the cell there is no external load A. Local action C. Self-discharge B. Polarization D. Electrolysis 339. ECE Board Exam November 1998 Type of power source in electronics that cannot be recharged after it has delivered its rated capacity A. Cells B. Primary cells C. Battery D. Secondary cells

340. ECE Board Exam November 1995 Which has the largest diameter of the following dry cells? A. Type C C. Type AAA B. Type AA D. Type D 341. ECE Board Exam April 1998 How many nickel-cadmium cells are needed in series for a 10 V battery? A. 8 C. 5 B. 12 D. 10 342. ECE Board Exam March 1996 Current in a chemical cell refers to the movement of _____. A. Negative ions only B. Negative and positive ions

C. D.

Positive ions only Negative hole charge

343. ECE Board Exam November 1998 Find the output of a two (2) lead acid cells. A. 0.952 V C. 3.2 V B. 2.1 V D. 4.2 V 344. ECE Board Exam November 2000 The liquid solution that forms ion charges in a lead acid battery A. Electrolyte C. Sulfuric acid B. Hydrochloric acid D. Nitric acid 345. ECE Board Exam April 1998 Single device that converts chemical energy into electrical energy is called A. Battery C. Solar B. Generator D. Cell 346. ECE Board Exam November 1995 There are _____ identical cells in parallel needed to double the current reading of each cells. A. 3 C. 2 B. 4 D. 1 347. ECE Board Exam April 2001 What is the effect of connecting battery cells in series? A. Voltage increases B. Current increases C. Voltage decreases D. Current decreases 348. ECE Board Exam November 2000 How long can a battery last with capacity of 50 ampere-hour running equipment of 5 amperes? A. 250 hours C. 100 hours B. 25 hours D. 10 hours 349. ECE Board Exam April 1998 How long will a battery need to operate a 240-watt equipment, whose capacity is 100 Ah and 24 volts rating? A. 10 hours C. 1 hour B. 5 hours D. 0.10 hour 350. ECE Board Exam November 2001 What is affected when a lead battery is overcharged? A. Carbon C. Plates B. Grid D. Electrolytes 351. ECE Board Exam November 1995 When the cells are in series voltages add, while current capacity is _____. A. The same as one cell B. Zero C. Infinite D. The sum of each cell 352. ECE Board Exam April 1999

Refers to an action in the operation of secondary cells reforming the electrodes in a chemical reaction where dc voltage is supplied externally. A. Polarizing cells B. Charging cells C. Aligning cells D. Discharging cells 353. ECE Board Exam November 1999 What type of cell that cannot be recharged which cannot restore chemical reaction? A. Primary cell B. Secondary cell C. Lead-acid wet cell D. Nickel-cadmium cell 354. ECE Board Exam November 2000 An ordinary flashlight battery is which of the following? A. A load C. A storage cell B. A dry cell D. A wet cell 355. ECE Board Exam April 1998 Refers to dry storage cell carbon zinc. A. cell B. Edison cell C. Mercury cell D. Nickel cadmium cell 356. ECE Board Exam April 1998 What is the other term of the secondary cells considering its capability to accept recharging? A. Reaction cell C. Storage cell B. Primary cell D. Dry cell 357. ECE Board Exam November 1996 Find the required battery capacity needed to operate an equipment of 30 amperes at 5 hours. A. 6 C. 3 B. 30 D. 150 358. ECE Board Exam March 1996 When batteries have cells connected in series the effect is A. Reduced output voltage B. Increased current supply C. Increased voltage supply D. Reduced internal resistance 359. ECE Board Exam November 2000 Find the required battery capacity needed to operate on electronic equipment with power rating of 200 watts and 10 volts at 6 hours. A. 60 C. 20 B. 1200 D. 120 360. ECE Board Exam November 2000 A cell(s) that can be operated or used in a horizontal, vertical or any position where its electrolyte cannot be spilled in any position A. Primary cells C. Dry cells B. Secondary cells D. Battery

361. ECE Board Exam April 1999 It is an indication of the current supplying capability of the battery for a specific period of time, e.g. 400 ampere-hour. A. Rating C. Capability B. Capacity D. Current load 362. ECE Board Exam March 1996 Which of the following is not a secondary type cell? A. Lithium C. Silver cadmium B. Lead-acid D. Silver-zinc 363. ECE Board Exam March 1996 How many lithium cells in series are needed for a 12 V battery? A. 12 cells C. 8 cells B. 4 cells D. 10 cells 364. ECE Board Exam November 1996 Component of solar battery which uses light energy to produce electromagnetic force A. Alkaline cell C. Lithium cell B. Polymer cell D. Selenium cell 365. ECE Board Exam March 1996 If a dry cell has an internal resistance of 0.50 ohm and emf of 2 volts, find power delivered in a one ohm resistor. A. 1.33 watts C. 3.66 watts B. 1.66 watts D. 1.77 watts 366. ECE Board Exam March 1996 Parallel cells have the same voltage as one cell but have _____. A. Unstable resistance B. Less current capability C. Fluctuating power output D. More current capacity 367. ECE Board Exam April 1999 A battery with capacity of 100 Ah and 12 volts rating will run an electronic equipment at exactly 20 hours, how much power is needed? A. 60 watts C. 10 watts B. 20 watts D. 30 watts 368. ECE Board Exam March 1996 It is the output voltage of a carbon-zinc cell. A. 3.5 V C. 1.5 V B. 2.5 V D. 0.5 V 369. ECE Board Exam March 1996 What is the reason why more cells can be stored in a given area with dynamic cells? A. They consume less power B. They are smaller C. They are larger D. They travel faster 370. ECE Board Exam November 1997 A radio equipment will be used at 70% at 50 amperes rating for 5 hours. How much capacity of dry battery is needed?

A. B.

35 17.5

C. D.

250 175

371. The potential at the terminals of the battery falls from 9 V on open circuit to 6 volts when a resistor of 10 ohms is connected across its terminals. What is the internal resistance of the battery? A. 5 Ω C. 3 Ω B. 4 Ω D. 2 Ω 372. A battery is formed of five cells joined in series. When the external resistance is 4 ohms, the current is 1.5 A and when the external resistance is 9 ohms, the current falls to 0.75 A. Find the internal resistance of each cell. A. 0.5 ohm C. 0.2 ohm B. 1.0 ohm D. 0.3 ohm 373. A 12 V source with 0.05  resistance is connected in series with another 12 volt with 0.075 Ω resistance with a load of 2 . Calculate the power dissipated in the load. A. 365 watts C. 105 watts B. 127 watts D. 255 watts 374. A 24 V source with 0.05  resistance is connected in parallel with another 24 V with 0.075  resistance to a load of 2 . Calculate the current delivered by the source with a 0.05  resistor. A. 7 amperes C. 5 amperes B. 10 amperes D. 12 amperes 375. A battery can deliver 10 joules of energy to move 5 coulombs of charge. What is the potential difference between the terminals of the battery? A. 2 V C. 0.5 V B. 50 V D. 5 V 376. An ordinary dry cell can deliver about ____ continuously. A. 3 A B. 2 A C. 1/8 A D. none of the above 377. Cells are connected in series when ____ is required. A. high voltage B. high current C. high voltage as well as high current D. none of the above 378. Cells are connected in series–parallel when ____ is required. A. high current B. high voltage C. high current as well a high voltage D. none of the above 379. Four cells, each of internal resistance 1 ohm, are connected in parallel. The battery resistance will be ____ A. 4 ohms C. 2 ohms B. 0.25 ohm D. 1 ohm

380. The e.m.f. of a cell depends upon ____ A. nature of electrodes and electrolyte B. size of electrodes C. spacing between electrodes D. none of the above 381. In order to get maximum current in series – parallel grouping, the external resistance should be ____ the total internal resistance of the battery. A. less than B. more than C. equal to D. none of the above 382. The positive terminal of a 6-V battery is connected to the negative terminal of a 12-V battery whose positive terminal is grounded. The potential at the negative terminal of the 6V battery is ____ volt. A. +18 C. -6 B. –12 D. -18 383. The positive terminal of a 6-V battery is connected to the negative terminal of a 12-V battery whose positive terminal is grounded. The potential at the positive terminal of the 6-V battery is ____ volt. A. +6 C. -12 B. -6 D. +12 384. Active materials of a lead-acid cell are A. lead peroxide B. sponge lead C. dilute sulfuric acid D. all of the above 385. During the charging of lead-acid cell A. its cathode becomes dark chocolate brown in colour B. its voltage increases C. it gives out energy D. specific gravity of H2SO4 is decreased 386. The ratio of Ah efficiency to Wh efficiency of a leadacid cell is A. always less than one B. just one C. always greater than one D. either A or B 387. The capacity of a cell is measured in A. watt-hours C. amperes B. watts D. ampere-hours 388. The capacity of a lead-acid cell does NOT depend on its A. rate of charge B. rate of discharge C. temperature D. quantity of active materials 389. As compared to constant-current system, the constant-voltage system of charging a lead-acid cell has the advantage of

A. B. C. D.

avoiding excessive gassing reducing time of charging increasing cell capacity both B and C

390. Sulphation in a lead-acid battery occurs due to A. trickle charging B. incomplete charging C. heavy discharging D. fast charging 391. The active materials of a nickel-iron battery are A. nickel hydroxide B. powdered iron and its oxides C. 21% solution of caustic potash D. all of the above 392. During charging and discharging of a nickel-iron cell A. its e.m.f. remains constant B. water is neither formed nor absorbed C. corrosive fumes are produced D. nickel hydroxide remains unsplit 393. As compared to a lead-acid cell, the efficiency of a nickel-iron cell is less due to its A. lower e.m.f. B. smaller quantity of electrolyte used C. higher internal resistance D. compactness 394. Trickle charging of a storage battery helps to A. prevent sulphation B. keep it fresh and fully charged C. maintain proper electrolyte level D. increase its reserve capacity 395. A dead storage battery can be revived by A. a dose of H2SO4 B. adding so-called battery restorer C. adding distilled water D. none of the above 396. The sediment which accumulates at the bottom of a lead-acid battery consist largely of A. lead-peroxide B. lead-sulphate C. antimony-lead alloy D. graphite 397. The reduction of battery capacity at high rates of discharge is primarily due to A. increase in its internal resistance B. decrease in its terminal voltage C. rapid formation of PbSO4 on the plates D. non-diffusion of acid to the inside active materials 398. Floating battery system are widely used for A. power stations B. emergency lighting C. telephone exchange installation D. all of the above

399. Any charge given to the battery when taken off the vehicle is called A. bench charge C. float charge B. step charge D. trickle charge 400. Storage battery electrolyte is formed by the dissolving of ____ acid in water. A. hydrochloric C. acetic B. sulfuric D. atric 401. The central terminal of a dry cell is said to be A. positive C. neutral B. negative D. charged 402. A 24 V battery of internal resistance r = 4 Ω is connected to a variable resistance R, the rate of heat dissipation in the resistor is maximum when the current drawn from the battery is I. Current drawn from the battery will be I/2 when R is equal to A. 8 Ω C. 16 Ω B. 12 Ω D. 20 Ω 403. What is the other term used for rechargeable battery? A. primary B. lead-acid C. storage D. nickel-cadmium E. NETWORK THEOREMS 404. REE Board Exam April 1997 A circuit consisting of three resistors rated: 10 ohms, 15 ohms and 20 ohms are connected in delta. What would be the resistance of the equivalent wye connected load? A. 0.30, 0.23 & 0.15 ohm B. 3.0, 4.0 & 5.0 ohms C. 3.33, 4.44 & 6.66 ohms D. 5.77, 8.66 & 11.55 ohms 405. EE Board Exam October 1994 The equivalent wye element of a 3 equal resistors each equal to R and connected in delta is A. R C. R/3 B. 3R/2 D. 3R 406. EE Board Exam April 1988 A Barangay power station supplies 60 kW to a load over 2,500 ft, 100 mm2, two-conductor copper feeder, the resistance of which is 0.078 ohm per 1000 ft. The bus bar voltage is maintained constant at 600 V. Determine the load current. A. 105 A C. 110 A B. 108 A D. 102 A 407. EE Board Exam October 1986 An LRT car, 5 km distance from the Tayuman station, takes 100 A over a 100 mm hard drawn copper trolley wire having a resistance of 0.270 ohm per km. The rail and ground return has a resistance of 0.06 ohm per km. If the station voltage is 750 V, what is the voltage of the car? A. 585 V C. 595 V

B.

590 V

D.

580 V

408. EE Board Exam April 1989 The LRT trolley system 10 miles long is fed by two substations that generate 600 volts and 560 volts, respectively. The resistance of the trolley wire and rail return is 0.3 ohm per mile. If the car is located 4 miles from the 600 volt station draws 200 A from the line. How much is the current supplied by each station? A. 133.33 A, 66.67 A B. 123.67 A, 76.33 A C. 117.44 A, 82.56 A D. 125.54 A, 63.05 A 409. EE Board Exam April 1992 In Manila, the LRT runs between Gil Puyat Station and Tayuman Station, which is 4 km apart and maintains voltages of 420 volts and 410 volts respectively. The resistance of go and return is 0.05 ohm per km. The train draws a constant current of 300 A while in motion. What are the currents supplied by the two stations if the train is at the distance of minimum potential? A. 175 A, 125 A C. 164 A, 136 A B. 183 A, 117 A D. 172 A, 123 A 410. EE Board Exam October 1986 An LRT car, 5 km distance from the Tayuman station, takes 100 A over a 100 mm hard drawn copper trolley wire having a resistance of 0.270 ohm per km. The rail and ground return has a resistance of 0.06 ohm per km. If the station voltage is 750 V, what is the efficiency of transmission? A. 78% C. 74% B. 81% D. 79% 411. EE Board Exam April 1988 A barangay power station supplies 60 kW to a load over 2,500 ft of 0002-conductor copper feeder the resistance of which is 0.078 ohm per 1,000 ft. The bus bar voltage is maintained constant at 600 volts. Determine the maximum power which can be transmitted. A. 220.35 kW C. 242.73 kW B. 230.77 kW D. 223.94 kW 412. EE Board Exam April 1991 Twelve similar wires each of resistance 2 ohms are connected so as to form a cube. Find the resistance between the two diagonally opposite corners. A. 1.45 ohms C. 2.01 ohms B. 1.66 ohms D. 1.28 ohms 413. EE Board Exam April 1991 Twelve similar wires each of resistance 2 ohms are connected so as to form a cube. Find the resistance between the two corners of the same edge. A. 1.133 ohms C. 1.125 ohms B. 1.102 ohms D. 1.167 ohms 414. EE Board Exam October 1991

Twelve identical wires each of resistance 6 ohms are arranged to form the edge of a cube. A current of 40 mA is led into the cube at one corner and out at the other diagonally opposite corners. Calculate the potential difference developed between these corners. A. 0.20 V C. 0.22 V B. 0.28 V D. 0.24 V 415. EE Board Exam August 1976 Find the value of the voltage V. 1Ω

0.1 Ω

24 V

Lamp 60 W 12 V

4Ω

V

+

12 V

G

-

A. B.

12.34 V 11.24 V

C. D.

12.19 V 11.66 V

416. EE Board Exam April 1982 Referring to the circuit diagram below, if the charger voltage is 130 volts and the battery voltage is 120 volts, solve for the current Ib. 3Ω +

Battery Charger

A. B.

Ib

2Ω

40 Ω Battery

-

-0.215 A 0.215 A

C. D.

-0.306 A 0.306 A

417. EE Board Exam August 1977 In the figure below R1 = 1 ohm, R2 = 1 ohm, R3 = 3 ohms, I2 = 2 A and VB = 120 V. Find Eg. R1

R2

I2 R3

+ Eg

G

VB

-

A. B.

182.41 V 153.32 V

C. D.

164.67 V 157.22 V

418. EE Board Exam October 1980, April 1984 In the dc circuit as shown, the high resistance voltmeter gives a reading of 0.435 volt. What is the value of the resistance R?

12 V

+

10 Ω

R +

20 Ω

V

-

50 Ω

A. B.

4 ohms 5 ohms

C. D.

3 ohms 2 ohms

419. EE Board Exam April 1980 Determine I in the figure. 20 Ω

D.

10 Ω 50 Ω

12 V 40 Ω

A. B.

0.028 A 0.010 A

I

B. C.

30 Ω

C. D.

0.025 A 0.014 A

420. ECE Board Exam April 1999 In Kirchhoff’s current law, which terminal of a resistance element is assumed to be at a higher potential (more positive) than the other? A. The terminal where the current exits the resistance elements B. The terminal where the current enters the resistance elements C. Either A or B can be arbitrarily selected D. The terminal closest to the node being analyzed 421. ECE Board Exam April 2000 According to Kichhoff’s current law, what is the algebraic sum of all currents entering and exiting a node. A. zero B. a negative value C. the algebraic sum of all currents D. a positive value 422. ECE Board Exam November 1997 Find the Thevenin’s impedance equivalent across R2 of a linear close circuit having 10 volts supply in series with the resistors (R1 = 100 ohms and R2 = 200 ohms). A. 6.66 ohms C. 66.6 ohms B. 6.666 kohms D. 666 ohms 423. ECE Board Exam April 1999 What is a node? A. A terminal point for a loop current B. A connection point between two or more conductors C. A formula D. A mathematical fiction 424. ECE Board Exam November 1998 If a resistance element is part of two loops, how many voltage drops must be calculated for that component? A. Two C. One B. Three D. None 425. ECE Board Exam April 1998 How many nodes are needed to completely analyze a circuit according to Kirchhoff’s current law? A. One

Two One less than the total number of nodes in the circuit All nodes in the circuit

426. ECE Board Exam November 1996 Find the Thevenin’s impedance equivalent across R 2 of a linear close circuit having 10 volt supply in series with two resistors (R1=50 ohms and R2 = 200 ohms). A. 400 ohms C. 4 ohms B. 40 ohms D. 4 kohms 427. ECE Board Exam November 1995 In order to match the load to the generator means making load resistance ______. A. lower than generator’s internal resistance B. increased to more generator’s internal resistance C. decreased D. equal to generator’s internal resistance 428. A circuit contains a 5 A current source in parallel with an 8 ohm resistor. What is the Thevenin’s voltage and Thevenin’s resistance of the circuit? A. 40 V, 8  C. 5 V, 8  B. 5/8 V, 40  D. 5/8 V, 8  429. In the Norton’s equivalent circuit, the source is a A. constant voltage source B. constant current source C. constant voltage, constant current D. none of these 430. The superposition theorem requires as many circuits to be solved as there are A. meshes B. source C. nodes D. all of the above 431. Three resistors of 6-ohm resistance are connected in delta. Inside the delta another 6-ohm resistors are connected in wye. Find its resistance between any two corners. A. 2 ohms C. 4 ohms B. 3 ohms D. 1 ohm 432. A 2-wire dc distribution line has sending end voltage of 240 V and total line resistance of 0.4 ohm. The maximum kW that can be transmitted by the line is ____. A. 108 C. 36 B. 72 D. 144 433. An active element in a circuit is one which ____. A. receives energy B. supplies energy C. both receives and supplies energy D. none of the above 434. An passive element in a circuit is one which ____. A. supplies energy

B. receives energy C. both receives and supplies energy D. none of the above

A. B. C. D.

E1

E2

one two

C. D.

R1

E1

A. B. C. D.

E2

Fig. 3.1 A. B. C. D.

R3

E1

R2 D

I2

one equation two equations

35 V

C E2

Fig. 3.1 A. B. C. D.

2Ω

40 V

Fig. 3.2 A. B.

439. The circuit shown in Fig. 3.1 has ____ branches.

R1

I1 I3

C. D.

three equations four equations

443. To solve the circuit shown in Fig. 3.2 by nodal analysis, we require ____ 3Ω 4Ω

three four two none of the above

A

E2

R2 D

two three four none of the above

35 V

C

R2 D

C

442. To solve the circuit shown in Fig. 3.2 by Kirchhoff’s laws, we require ____ 3Ω 4Ω

three four

R3

R3

E1

438. In the circuit shown in Fig. 3.1, there are ____ junctions.

A

R1

A

Fig. 3.1

Fig. 3.1 A. B.

two four three none of the above

C

R2 D

E2

R2 D

441. In the circuit shown in Fig. 3.1, there are ___ meshes.

437. In the circuit shown in Fig. 3.1, the number of nodes is ____

R3

C

Fig. 3.1

436. A linear circuit is one whose parameters (e.g. resistances etc.) ____. A. change with change in current B. change with change in voltage C. do not change with change in voltage and current D. none of the above

R1

R3

E1

435. An electric circuit contains ____. A. active elements only B. passive element only C. both active and passive elements D. none of the above

A

R1

A

two four three none of the above

440. The circuit shown in Fig. 3.1 has ____ loops.

A. B. C. D.

I1 I3

2Ω

I2

40 V

Fig. 3.2 one equation two equation three equations none of the above

444. To solve the circuit shown in Fig. 3.2 by superposition theorem, we require ____ 3Ω 4Ω

35 V

I1 I3

2Ω Fig. 3.2

I2

40 V

A. B. C. D.

one circuit two circuits three circuits none of the above

445. To solve the circuit shown in Fig. 3.2 by Maxwell’s mesh current equation, we require 3Ω 4Ω

35 V

I1 I3

2Ω

I2

40 V

449. The superposition theorem is used when the circuit contains A. a single voltage source B. a number of passive source C. passive elements only D. none of the above 450. Fig. 3.4(b) shows the Thevenin’s equivalent circuit of Fig. 3.4(a). The value of Thevenin’s voltage Vth is ____. 4Ω 40 V

Fig. 3.2 A. B. C. D.

5Ω

A. B.

2Ω D

I2

20 V 24 V

C. D.

451. The value of Rth in Fig. 3.4(b) is ____. 4Ω

5Ω

A. B.

I2

(b)

15 Ω 3.5 Ω

C. D.

6.4 Ω 7.4 Ω

4Ω

Fig. 3.3

40 V

20 V

C. D.

2Ω D

5Ω

Rth

A RL

6Ω

A

Vth

RL B

(a)

(b) Fig. 3.4

10 A 5A

one equation two equation three equations none of the above

RL B

B

2A 2.5 A

448. In order to solve the circuit shown in Fig. 3.3 by nodal analysis, we require 3Ω B 2Ω

A. B. C. D.

Vth

Fig. 3.4

Fig. 3.3

30 V

RL

6Ω

A

452. The open-circuited voltage at terminals AB in Fig. 3.4(a) is

2Ω D

I1 I3

Rth

A

B

447. The current in 2 Ω horizontal resistor in Fig. 3.3 is ____. 3Ω B 2Ω

A. B.

12 V 36 V

(a)

2A 5A 2.5 A none of the above

I1 I3

(b)

20 V

Fig. 3.3

30 V

RL B

Fig. 3.4

40 V

A. B. C. D.

A

Vth

(a)

446. In the circuit shown in Fig. 3.3, the voltage at node B wrt D is calculated to be 15 V. The current in the 3 Ω resistor will be 3Ω B 2Ω 30 V

RL

6Ω B

one equation three equations two equations none of the above

I1 I3

Rth

A

I2

A. B.

12 V 20 V

C. D.

24 V 40 V

453. For transfer of maximum power in the circuit shown in Fig. 3.4(a), the value of RL should be ____. 4Ω

5Ω

40 V

Rth

A RL

6Ω

Vth

RL B

B

20 V

A

(a)

(b) Fig. 3.4

A. B.

3.5 Ω 6.4 Ω

C. D.

7.4 Ω 15 Ω

454. Fig. 3.5(b) shows Norton’s equivalent circuit of Fig. 3.5(a). The value of RN is ____.

12 V

RL

6Ω

Rth

A

A IN

RN

RL

B

B (a)

RN = 3 Ω

3Ω

IN = 2 A

2Ω

A. B.

3V 6V

462. The value of Rth in Fig. 3.6(b) is ____.

RL

6Ω

IN = 2 A

A

A IN

RN

(a)

RL

Fig. 3.5

3A 1A 2A none of the above

458. In the analysis of a vacuum tube circuit, we generally use ____. A. superposition C. Thevenin’s B. Norton’s D. reciprocity 459. Norton’s theorem is ____ form of an equivalent circuit A. voltage B. current C. both voltage and current D. none of the above 460. In the analysis of a transistor circuit, we generally use ____. A. Norton’s C. reciprocity B. Thevenin’s D. superposition 461. Fig. 3.6(a) shows Norton’s equivalent circuit of a network whereas Fig. 3.6(b) shows its Thevenin’s equivalent circuit. The value of Vth is ____.

A

Vth B

B (b)

Fig. 3.6

A. B.

3Ω 2Ω

C. D.

1.5 Ω 6Ω

463. If in Fig. 3.6(a), the value of IN is 3 A, then value of Vth in Fig. 3.6(b) will be ____. Rth IN = 2 A

456. Thevenin’s theorem is ____ form on an equivalent circuit. A. voltage B. current C. both voltage and current D. none of the above 457. Norton’s theorem is ____ Thevenin’s theorem. A. the same as B. converse of C. equal to D. none of the above

A

(a)

B (b)

RN = 3 Ω

Rth

B

A. B. C. D.

C. D.

RN = 3 Ω

12 V

B (b)

1.5 V 0.866 V

455. The value of IN in Fig. 3.5(b) is ____. 3Ω

B Fig. 3.6

5Ω 4.5 Ω 10.5 Ω none of the above 2Ω

A

Vth

(a)

(b) Fig. 3.5

A. B. C. D.

A

A

A

Vth B

(a)

B (b)

Fig. 3.6

A. B. C. D.

1V 9V 5V none of the above

464. For maximum power transfer, the relation between load resistance RL and internal resistance Ri of the voltage source is ____. A. RL = 2Ri C. RL = 1.5Ri B. RL = 0.5Ri D. RL = Ri 465. Under the conditions of maximum power transfer, the efficiency is ____. A. 75% C. 50% B. 100% D. 25% 466. The open-circuited voltage at terminals of load RL is 30 V Under the conditions of maximum power transfer, the load voltage would be ____. A. 30 V C. 5 V B. 10 V D. 15 V 467. The maximum power transfer theorem is used in ____. A. electronic circuits B. power system C. home lighting circuits D. none of the above

468. Under the conditions of maximum power transfer, a voltage source is delivering a power of 30 W to the load. The power generated by the source is ____. A. 45 W C. 60 W B. 30 W D. 90 W 469. For the circuit shown in Fig. 3.7, the power transferred will be maximum when RL is equal to ____. 3Ω 4Ω A 18 V

RL

6Ω B

4.5 Ω 6Ω 3Ω none of the above

470. The open-circuited voltage at terminals AB in Fig. 3.7 is ____. 3Ω 4Ω A 18 V

RL

6Ω B Fig. 3.7

A. B.

12 V 6V

C. D.

15 V 9.5 V

471. If in Fig. 3.7, the value of RL = 6 Ω, then current through RL is ____. 3Ω 4Ω A 18 V

RL

6Ω B Fig. 3.7

A. B.

2A 1.5 A

C. D.

1.75 A 1A

472. Under the conditions of maximum power transfer, the voltage across RL in Fig. 3.7 is ____. 3Ω 4Ω A 18 V

RL

6Ω B Fig. 3.7

A. B.

6V 4V

C. D.

475. Kirchhoff’s current law is applicable to only A. closed loops in a network B. electronic circuits C. conjunctions in a network D. electric circuits 476. Kirchhoff’s voltage law is concerned with A. IR drops B. battery e.m.f.s. C. junction voltages D. both A and B

Fig. 3.7

A. B. C. D.

474. Delta/star of star/delta transformation technique is applied to ___. A. one terminal B. two terminal C. three terminal D. none of the above

9V 12 V

473. The output resistance of a voltage source is 4 Ω. Its internal resistance will be ____. A. 4 Ω C. 1 Ω B. 2 Ω D. infinite

477. According to KVL, the algebraic sum of all IR drops and e.m.f.s in any closed loop of a network is always A. B. C. D.

zero positive negative determined by the battery e.m.f.s

478. The algebraic sign of an IR drop is primarily dependent upon the A. amount of current flowing through it B. value of R C. direction of current flow D. battery connection 479. Maxwell’s loop current method of solving electrical networks A. uses branch currents B. utilizes Kirchhoff’s voltage law C. is confined to single-loop circuits D. is a network reduction method 480. Point out the WRONG statement. In the nodevoltage technique of solving networks, choice of a reference node does not A. affect the operation of the circuit B. change the voltage across any element C. alter the p.d. between any pair of nodes D. affect the voltages of various nodes 481. The nodal analysis is primarily based on the application of A. KVL C. Ohm’s Law B. KCL D. both B and C 482. Superposition theorem is can be applied only to circuits having ____ elements. A. non-linear C. linear bilateral B. passive D. resistive 483. The Superposition theorem is essentially based on the concept of A. duality C. reciprocity

B.

linearity

D.

non-linearity

B.

3 A, 2 Ω

D.

3 A, 9 Ω

484. While Thevenizing a circuit between two terminals, Vth equals A. short-circuit terminal voltage B. open circuit terminal voltage C. EMF of the battery nearest to the terminal D. net voltage available in the circuit

490. The Norton equivalent of a circuit consists of a 2 A current source in parallel with a 4  resistor. Thevenin equivalent of this circuit is a ____ volt source in series with a 4  resistor. A. 2 C. 6 B. 0.5 D. 8

485. Thevenin resistance Rth is found A. between any two “open” terminals B. by short-circuiting the given two terminals C. by removing voltage sources along with their internal resistance D. between same open terminals as for Vth

491. If two identical 3 A, 4  Norton equivalent circuits are connected in parallel with like polarity to like, the combined Norton equivalent circuit is A. 6 A, 4  C. 3 A, 2 Ω B. 6 A, 2  D. 6 A, 8 Ω

486. While calculating Rth, constant-current sources in the circuit are A. replaced by “opens” B. replaced by “shorts” C. treated in parallel with other voltage sources D. converted into equivalent voltage sources 487. Thevenin resistance of the circuit of Fig. 2.1 across its terminals A and B is ____ ohm. 3Ω A 12 V

3Ω

B

A. B.

Fig. 2.1

6 3

C. D.

9 2

492. Two 6 V, 2  batteries are connected in series aiding. This combination can be replaced by a single equivalent current generator of ____ with a parallel resistance of ____ ohm. A. 3 A, 4  C. 3 A, 1 Ω B. 3 A, 2  D. 5 A, 2 Ω 493. Two identical 3 A, 1  batteries are connected in parallel with like polarity with like polarity to like. The Norton equivalent circuit of the combination is A. 3 A, 0.5  C. 3 A, 1 Ω B. 6 A, 1  D. 6 A, 0.5 Ω 494. Thevenin equivalent circuit of the network shown in Fig. 2.3 is required. The value of the open-circuit voltage across terminals a and b of this circuit is ____ volt. 5Ω a

488. The load resistance needed to extract maximum power from the circuit of Fig. 2.2 is ____ ohm.

+ -

A

10 Ω

2i

b

6Ω 3Ω

Fig. 2.3 A. B.

18 V

B

Fig. 2.2 A. B.

2 9

C. D.

6 18

489. The Norton equivalent circuit for the network of Fig. 2.2 between A and B is ____ current source with parallel resistance of ____. A

6Ω

18 V

B

Fig. 2.2 2 A, 6 Ω

C.

C. D.

2i/5 2i/15

495. For a linear network containing generators and impedance, the ratio of the voltage to the current produced in other loop is the same as the ratio of voltage and current obtained when the positions of the voltage source and the ammeter measuring the current are interchanged. This network theorem is known as ____ theorem. A. Millman’s C. Tellegen’s B. Norton’s D. Reciprocity 496. A 12 volt source with an internal resistance of 1.2 ohms is connected across a wire-wound resistor. Maximum power will be dissipated in the resistor when its resistance is equal to A. zero C. 12 ohms B. 1.2 ohm D. infinity

3Ω

A.

zero 2i/10

2 A, 3 Ω

497. Three 3.33  resistors are connected in wye. What is the value of the equivalent resistors connected in delta? A. 3.33  C. 6.67  B. 10  D. 20  498. Find the equivalent resistance between terminals a & b of the circuit shown. Each resistance has a value of 1 ohm.

A. B.

10.0 ohms 3.875 ohms

C. D.

0.968 ohms 1.60 ohms

503. Determine the value VO in the ideal op-amp circuit below.

A. B.

5/6 ohms 5/11 ohms

C. D.

5/14 ohms 5/21 ohms

499. What do you call the head to tail connection of two or more op-amp circuits wherein the output of one opamp is the input of another op-amp? A. Parallel Op-Amps B. Follow-Thru Connection C. Cascade Connection D. Series Op-Amps

A. B.

-8 V -6 V

C. D.

-4 V -3 V

504. Determine the value VO in the op-amp circuit below.

500. Find the power dissipation in the 6 ohms resistor in the next figure.

A. B. A. B.

54 W 216 W

C. D.

121.5 W 150 W

501. Determine the value of node voltage V2. All resistances are in ohms.

A. B.

14 V 12 V

C. D.

0V 1V

502. What should be the value of R so the resistor will receive the maximum power? All resistances are in ohms.

-4 V -8 V

C. D.

-2 V -3 V

505. If the voltage source (dependent or independent) is connected between two non-reference nodes, the two non-reference nodes form a ______ A. Common Node B. Supernode C. Complex Node D. Reference node 506. The theorem that states that “the voltage across or current through an element in a linear circuit is the algebraic sum of the voltages across or current through that element due to each independent source acting alone”. A. Superposition Theorem B. Thevenin’s Theorem C. Norton’s Theorem D. Reciprocity Theorem 507. Kirchhoff’s Current Law states that A. the algebraic sum of the currents flowing into any point in a circuit must equal zero B. the algebraic sum of the currents entering and leaving any point in a circuit must equal zero C. the algebraic sum of the currents flowing away from any point in a circuit must equal zero

D.

the algebraic sum of the currents around any closed path must equal zero

508. When applying Kirchhoff’s Current Law, A. consider all the currents flowing into a branch point positive and all currents directed away from that point negative B. consider all the currents flowing into a branch point negative and all currents directed away from that point positive C. remember that the total of all the currents entering a branch point must always be greater than the sum of the currents leaving that point D. the algebraic sum of the currents entering and leaving a branch point does not necessarily have to be zero 509. When applying Kirchhoff’s Voltage Law, a closed path is commonly referred to as a A. node C. loop B. principal node D. branch point 510. Kirchhoff’s Voltage Law states that A. the algebraic sum of the voltage sources and IR voltage drops in any closed path must total zero B. the algebraic sum of the voltage sources and IR voltage drops around any closed path can never equal zero C. the algebraic sum of all the currents flowing around any closed path must equal zero D. none of the above 511. When applying Kirchhoff’s Voltage Law A. consider any voltage whose positive terminal is reached first as negative and any voltage whose negative terminal is reached first as positive B. C. D.

always consider all voltage sources as positive and all resistor voltage drops as negative consider any voltage whose negative terminal is reached first as negative and any voltage whose positive terminal is reached first as positive always consider all resistor voltage drops as positive and all voltage sources as negative

512. The algebraic sum of +40 V and -30 V is A. -10 V C. +70 V B. +10 V D. -70 V 513. A principal node is A. a closed path or loop where the algebraic sum of the voltages must equal zero B. the simplest possible closed path around a circuit C. a junction where branch current can combine or divide D. none of the above 514. How many equations are necessary to solve a circuit with two principal nodes? A. 3 C. 4 B. 2 D. 1

515. The difference between a mesh current and a branch current is A. a mesh current is an assumed current and a branch current is an actual current B. the direction of the current themselves C. a mesh current does not divide at a branch point D. both A and B above 516. Using the method of mesh currents, any resistance common to two meshes has A. two opposing mesh currents B. one common mesh current C. zero current D. none of the above 517. The fact that the sum of the resistor voltage drops equals the applied voltage in a series circuit is the basis for A. Kirchhoff’s Current Law B. node voltage analysis C. Kirchhoff’s Voltage Law D. the method of mesh currents 518. The fact that the sum of the individual branch currents equals the total current in a parallel circuit is the basis for A. Kirchhoff’s Current Law B. node voltage analysis C. Kirchhoff’s Voltage Law D. the method of mesh currents 519. If you do not go completely around the loop when applying Kirchhoff’s Voltage Law, then A. the algebraic sum of the voltages will always be positive B. the algebraic sum is the voltage between the start and finish points C. the algebraic sum of the voltages will always be negative D. the algebraic sum of the voltages cannot be determined 520. A resistor is an example of a(n) A. bilateral component B. active component C. passive component D. both A and C 521. To apply Superposition theorem, all components must be A. the active type B. both linear and bilateral C. grounded D. both nonlinear and unidirectional 522. When converting from a Norton-equivalent circuit to a Thevenin equivalent circuit or vice versa A. RN and RTH have the same value B. RN will always be larger than RTH C. IN is shorted-circuit to find VTH D. VTH is short-circuited to find IN

523. When solving for the Thevenin equivalent resistance, RTH, A. all voltage sources must be opened B. all voltage sources must be short-circuited C. all voltage sources must be converted to current sources D. none of the above 524. Thevenin’s Theorem states that an entire network connected to a pair of terminals can be replaced with A. a single current source in parallel with a single resistance B. a single voltage source in parallel with a single resistance C. a single voltage source in series with a single resistance D. a single current source in series with a single resistance 525. Norton’s Theorem states that an entire network connected to a pair of terminals can be replaced with A. a single current source in parallel with a single resistance B. a single voltage source in parallel with a single resistance C. a single voltage source in series with a single resistance D. a single current source in series with a single resistance 526. With respect to terminals A and B in a complex network, the Thevenin voltage, VTH, is A. the voltage across terminals A and B when they are short-circuited B. the open-circuit voltage across terminals A and B C. the same as the voltage applied to the complex network D. none of the above 527. With respect to terminals A and B in a complex network, the Norton current, IN, is A. the current flowing between terminals A and B when they are open B. the total current supplied by the applied voltage to the network C. zero when terminals A and B are short-circuited D. the current flowing terminals A and B when they are short-circuited

530. Electrical appliances are connected in parallel because it ____ A. is a simple circuit B. draws less current C. results in reduce in power loss D. makes the operation of appliances independent of each other 531. The purpose of load in an electric circuit is to ____ A. increase the circuit current B. utilize electrical energy C. decrease the circuit current D. none of the above 532. A passive network has A. no emf source B. no current source C. neither emf nor current source D. none of these 533. The relationship between voltage and current is the same for two opposite directions of current in case of A. B. C. D.

bilateral network active network unilateral network passive network

534. Which of the following statement is not correct? A. voltage source is an active element B. current source is a passive element C. resistance is a passive element D. conductance is a passive element 535. A resistance R is connected across two batteries, A and B connected in parallel. The open circuit emfs and internal resistances of the batteries are 12 V, 2 ohms and 8 V, 1 ohm respectively. Determine the ohmic value of R if the power absorbed by R is 7.656 watts. A. 10  C. 9  B. 12  D. 8  536. A network has 7 nodes and 5 independent loops. The number of branches in the network is A. 13 C. 11 B. 12 D. 10

528. Which theorem provides a shortcut for finding the common voltage across any number of parallel branches with different sources? A. The Superposition Theorem B. Thevenin’s Theorem C. Norton’s Theorem D. Millman’s Theorem

537. The nodal method of circuit analysis is based on A. Kirchhoff’s Voltage Law & Ohm’s law B. Kirchhoff’s Current Law & Ohm‘s law C. Kirchhoff’s Current Law & Kirchhoff’s Voltage Law D. Kirchhoff’s Current Law & Kirchhoff’s Voltage Law & Ohm‘s law

529. A d.c. circuit usually has ____ as the load A. Resistance B. Capacitance C. Inductance D. both inductance and capacitance

538. For a network of seven branches and four nodes, the number of independent loops will be A. 11 C. 7 B. 8 D. 4

539. A network has b branches and nodes. For this mesh analysis will be simpler then node analysis if n is greater then A. b C. (b/2) + 1 B. b + 1 D. b/2 540. The number of independent loops for a network with n nodes and b branches is A. n - 1 B. b - n C. b - n + 1 D. independent no. of nodes

A. B.

2R R

C. D.

R/2 3R

548. Find Rab. All values are in ohms.

541. The following constitutes a bilateral element A. Resistor C. Vacuum Tube B. FET D. metal rectifier 542. Kirchhoff’s Laws fail in the case of A. linear networks B. non-linear networks C. dual networks D. distributed parameter networks 543. Ohm’s law, Kirchhoff’s Current Law & Kirchhoff’s Voltage will fail at A. Low frequency C. high power B. high frequency D. none of these

A. B.

22.5 40

C. D.

30 none of these

549. Find the equivalent resistance of the circuit in the figure.

544. Total no, of mesh equations required is equal to A. number of links B. number of tree branches C. number of nodes D. none of these 545. The minimum number of equations required to analyze the circuit A. B.

3 ohms 4 ohms

C. D.

5 ohms 6 ohms

550. Find the equivalent resistance of the circuit in this figure.

A. B.

3 4

C. D.

6 7

546. Equivalent impedance seen across terminals a, b is A. B.

R 2R

C. D.

3R 4R

551. Find the total resistance Rin is in the circuit shown .

A. B.

16/3 Ω 8/3 Ω

C. D.

8/3 + j12 none of these

547. What is the Rab in the circuit when all resistors values are R?

A. B.

𝟏 + √𝟑 (1 − √5)/2

552. What is the value of i1?

C. D.

(−1 + √5)/2 none of these

A. B.

0 –6

C. D.

6 none of these

553. Find Ix in the circuit shown.

A. B.

+3V –3V

C. D.

2V none of these

C. D.

97.3 V 103 V

559. Determine VX of this circuit

A. B.

3A –3 A

C. D.

0 none of these

554. Find value of R in the given circuit. A. B.

42.2 V 83.3 V

560. Find voltage eo in the fig shown. A. B.

8.2 Ω 6Ω

C. D.

10 Ω none of these

555. The voltage V in the figure always equal to

A. B.

2V 4/3 V

C. D.

4V 8V

C. D.

0V 10 V

C. D.

36 V 28 V

C. D.

aeat – bebt aeat + bebt

561. Find VX in the circuit shown

A. B.

9V 5V

C. D.

1V none of these

556. Find V in the circuit shown.

A. B.

2.5 V -2.5 V

562. Find voltage eo in the fig shown

A. B.

2V 3V

C. D.

1V none of these A. B.

557. Find V in the circuit shown.

48 V 24 V

563. The voltage v(t) is

A. B.

–3V +3 V

558. Find V in the circuit shown.

C. D.

2V none of these

A. B.

eat – e-bt eat + ebt

564. Find current through 5 Ω resistor

569. Find i2 in the figure shown.

A. B.

0 2A

C. D.

3A 7A

565. Find Vxy A. B.

A. B.

10 V 46 V

C. D.

13 V 58 V

566. What is VAB?

4A 2/3 A

C. D.

-2/3 A none of these

570. When a resistor R is connected to a current source, it consumes a power of 18 W. When the same R is connected to a voltage source having same magnitude as the current source, the power absorbed by R is 4.5 W. The magnitude of the current source & value of R are A. √18 A & 1 ohm C. 1 A & 18 ohms B. 3 A & 2 ohms D. 6 A & 0.5 ohms 571. In the circuit shown in the figure. If I = 2, then the value of the battery voltage V will be

A. B.

3V 54V

C. D.

24 V none of these

567. What is Vxy?

A. B.

5V 3V

C. D.

2V 1V

572. Find E and I in the figure shown.

A. B.

20 V 30 V

C. D.

–10 V 10 V

568. In the circuit of the given figure. The value of the voltage source E is

A. B. C. D.

I = 13 A and E = 31 V I = 31 A and E = 13V E = 31 V and I = 31A none of these

573. Find the voltage across the terminals a and b.

A. B.

0.5 V 3.0 V

C. D.

3.5 V 4.0 V

574. What is the current supplied by 1 V source when each resistance is 1 ohm?

A. B.

–16 V 4V

C. D.

–6 V 16 V

A. B. A. B.

8/15 A 15/4 A

C. D.

4/15 A none of these

C. D.

5V none of these

56.25 V 85 V

C. D.

40 V none of these

C. D.

-4 V 4V

580. What is VA?

575. The voltage V is equal to

A. B.

3V –3 V

576. The voltage across 15 ohms resistor is

A. B.

-105 V +105 V

C. D.

–15 V + 15 V

577. In the circuit of the given figure. The current I will be

A. B.

-2 V 2V

581. What is the value of I4 in the fig shown?

A. B. C. D.

–4 A –2 A known only if V1, V2 and R are known known only if V1, V2 are known

582. If the voltage of each source in the given network is doubled, then which of the following statement would be true? A. B.

1A 2A

C. D.

4A 8A

578. In the circuit shown in the given figure, the potential difference V2 – V1 is

A. B.

–4.5 V 0

579. Find V in the figure shown.

C. D.

4.5 V 6V

1. 2. 3. 4. A. B.

Current flowing in the network will be doubled Voltages across each resistor will be doubled Power absorbed by each resistor will be doubled Power delivered by each source will be doubled 1, 2, 3, 4 C. 2, 3 1, 2 D. 1, 3, 4

583. For a given network, the number of independent mesh equation (Nm) and the number of independent node equation (Nn) obey the following:

A. B. C. D.

Nm = Nn Nm > Nn Nm < Nn any one of the above, depending on the network

589. A 35 V source is connected to a series circuit of 600Ω and R as shown. If a voltmeter of internal resistance1.2 kΩ is connected across 600 Ω resistor it reads 5 V, find the value of R.

584. In the circuit of the given figure. What is the current I?

A. B. A. B.

1A 4/3 A

C. D.

2A 3A

1.2 kΩ 2.4 kΩ

C. D.

3.6 kΩ 7.2 kΩ

590. Find the current in RL in the circuit below.

585. Find the value of R for which the power supplied by the voltage source is zero.

A. B. A. B.

0 1.5 ohms

C. D.

6 ohms 0.667 ohms

0 2/3

C. D.

1/3 none

591. The current flowing through the voltage source in the given circuit is

586. What value of R which ensures that the current through the 60 ohm resistor of this circuit is 1 A?

A. B. A. B.

5 ohms 10 ohms

C. D.

15 ohms 20 ohms

1.0 A 0.75 A

C. D.

0.5 A 0.25 A

592. In the circuit shown, the voltage across 2Ω resistor is 20 V. The 5 Ω resistor connected between the terminals A and B can be replaced by an ideal

587. The current I in the circuit of the figure is

A. B.

2A 1.5 A

C. D.

0.5 A 0A

588. In the circuit shown in the given figure, current I is

A. B. C. D.

Voltage source of 25 V with +ve terminal upward Voltage source of 25 V with +ve terminal downward Current source of 2 A upward Current source of 2A downward

593. In the circuit shown in the figure. The effective resistance faced by the voltage source is

A. B.

–2/5 24/5

C. D.

18/5 2/5 A.

1Ω

C.

3Ω

B.

2Ω

D.

3.3 Ω

594. If a resistance ‘R’ of 1Ω is connected across the terminals AB as shown in the given fig. Then the current flowing through R will be A. B.

–150 150

C. D.

100 50

599. When R = 10 ohms, VR = 20 V, when R = 20 ohms VR = 30 V. Find VR when R = 80 ohms. A. B.

1A 0.5 A

C. D.

0.25 A 0.125 A

595. Find VL across the ¼ ohm resistor of this circuit.

A. B.

40 160

C. D.

48 none

C. D.

6 V, 6 V 12 V, 12 V

600. Find V1 & V2.

A. B.

1/52 V 2/52 V

C. D.

3/52 V 5/52 V

596. Find Ix in the fig shown

A. B.

1A –2 A

1W 5W

4 V, 8 V 8 V, 4 V

601. The network shown in the figure draws current I when ab is open. If the ends ab were shorted, the current drawn would be

C. D.

2A none of these

597. A particular resistor R dissipates a power of 4W when V alone is active. The same resistor R dissipates a power of 9 watts when I alone is active. The power dissipated by R when both sources are active will be

A. B.

A. B.

C. D.

A. B.

∞ 4I

C. D.

2I I

602. In the figure below, the voltage across the 18 ohm resistor is 90 volts. What is the total voltage across the combined circuit?

13 W 25 W

598. The linear network contains only resistors if is1 = 8A, is2 = 12A, Vx is found to be 80v. If is1 = -8A, is2 = 4A, Vx = 0 . Find Vx when is1 = is2 = 20A.

A. B.

125 V 16 V

C. D.

24 V 40 V

603. Find the current transfer ratio I2/I1 for the network shown in the figure. All resistors are given as 2 ohms.

A. B.

A. B.

0.25 0.40

C. D.

0.50 0.75

604. In the network shown in the given figure, the effective resistance faced by the voltage source is

A. B.

4 ohms 3 ohms

C. D.

2 ohms 1 mega ohms

605. The V-I relation for the network shown in the given box is V = 4I - 9. If now a resistor R = 2 ohms is connected across it, then the value of I will be

A. B.

–4.5 A –1.5 A

C. D.

1.5 A 4.5 A

606. In the circuit shown in the figure, for R = 20 ohms the current I is 2 A. When R is 10 ohms the current I would be

A. B.

1A 2A

C. D.

10 ohms 18 ohms

C. D.

24 ohms 12 ohms

608. An ideal constant voltage source is connected in series with an ideal constant current source. Considered together, the combination will be a A. constant voltage source B. constant current source C. constant voltage source and constant current D. source or a constant power source 609. A network contains only independent current sources and resistors. If the values of all the resistors are doubled, the values of the node voltage A. will become half B. will remain unchanged C. will become double D. cannot be determined unless the circuit configuration and the values of the resistors are known 610. A network N is a dual of network N if A. both of them have same mesh equations B. both of them have same node equations C. mesh equations of one are the node equations of the other D. KCL and KVL equations are the same 611. A certain network consists of two ideal voltage sources and a large number of ideal resistors. The power consumed in one of the resistor is 4 W when either of the two sources is active and the other is replaced by a short circuit. The power consumed by the same resistor when both the sources are simultaneously active would be A. zero or 16 W C. zero or 8 W B. 4W or 8 W D. 8 W or 16 W 612. All the resistances in the circuit are R ohms each. The switch is initially open. What happens to the lamp intensity when the switch is closed?

2.5 A 3A

607. In the figure, the value of R is A. B. C. D.

increases decreases remain constant depends on the value of R

613. If R1 = R2 = R4 = R and R3 = 1.1R in the bridge circuit shown in figure, then the reading in the ideal voltmeter connected across a and b is

A. B.

0.238 V 0.138 V

C. D.

–0.238 V 1V

614. A network has b branches and n nodes. For this mesh analysis will be simpler than node analysis if n is greater than A. b C. b/2 +1 B. b + 1 D. b/2

A. B. C. D.

power supplied by both the sources is same current flowing through 5 Ω resistors are same current flowing through 1 Ω resistors are same all are correct

619. Practical current source internal resistance should be A. Less than RL C. equal to RL B. greater than RL D. none of these 620. The equivalent circuit of the following circuit is

615. Match the following

A. B. C. D.

I1/I2 P1/P2 P1 in Watts P2 in Watts

A. B.

ABCD 3541 2341

1. 2. 3. 4. 5. C. D.

600 0.3 2 500 1.2 ABCD 3514 1314

616. Find single current source equivalent.

A. B.

1 A, 2.73 Ω 2.73 A, 1 Ω

C. D.

A. B. C. D.

V in series with 3R 3V in series with 3R V in series with R/3 3V in series with R/3

621. Obtain potential of node B with respect to G in the network shown in figure.

5A, 30/11 Ω none of these

617. The value of equivalent voltage and resistance across a and b.

A. B.

64/63 V 1V

C. D.

63/64 V 32/63 V

622. Find power dissipated in resistor 1 Ω.

A. B.

– 100 V, 30 Ω - 2 V, 30 Ω

C. D.

10/3 V, 30 Ω none of these

618. Identify correct statement with respect to fig. (a) and (b). A. B.

0 6W

C. D.

9W none of these

623. Find power delivered at t = 0.8 s.

A. B.

51 W 34.68 W

C. D.

– 34.68 W none of these

624. The total power consumed in the circuit shown in the figure is

A. B.

4A -4 A

C. D.

2A none of these

629. The dependent current source shown

A. B.

Delivers 80 W absorbs 80 W

C. D.

delivers 40 W absorbs 40 W

630. Find power absorbed by dependent source. A. B.

10 W 12 W

C. D.

16 W 20 W

625. In the circuit shown in the given figure, power dissipation in the 5 Ω resistor is A. B.

–3 W 3W

C. D.

0W none of these

631. What is the power supplied by 2 A current source. A. B.

zero 80 W

C. D.

125 W 405 W

626. Find the total power absorbed by all resistors in the circuit shown.

A. B.

15 W 20 W

C. D.

25 W 30 W

627. What will be the power consumed by the voltage source, current source and resistance respectively

A. B.

1 W, 1 W, 2 W 0 W, -1 W, 1 W

C. D.

1 W, 0 W, 1 W 0 W, 0 W, 0 W

628. Power absorbed by 6 Ω resistor is 24 W. Determine Io

A. B.

–70 W 70 W

C. D.

50 W none of these

632. Each branch resistance is 1 ohm. Find equivalent resistance in each path out of 3 paths.

A. B.

15/6 ohms 5/6 ohms

C. D.

6/5 ohms none of these

633. If each branch of a delta circuit has impedance √3 Z, then each branch of the equivalent Wye circuit has impedance A. Z/√𝟑 C. 3√3 Z B. 3Z D. Z/3

634. A delta–connected network with its WYE-equivalent is shown. The resistances R1 R2 & R3 are A. B.

A. B.

1.5 Ω, 3 Ω, 9 Ω 3 Ω, 6 Ω, 1.5 Ω

C. D.

9 Ω, 3 Ω, 1.5 Ω 3 Ω, 1.5 Ω, 9 Ω

635. When all resistances in delta connection are having equal value of R. What is the equivalent resistance in star connection? A. RY = RΔ C. RY = RΔ/3 B. RΔ = RY/3 D. none of these 636. The effective resistance between the terminals A and B in the circuit shown in the figure is (all resistors are equal to R)

A. B.

R R-1

C. D.

R/2 (6/11) R

637. What is the equivalent resistance between AB when each branch resistance is 2 ohms?

A. B.

3.23 ohm 2 ohm

C. D.

difficult to find none of these

638. Superposition theorem is not applicable in the network when it is A. Linear C. Time varying B. non-linear D. Time invarying 639. The superposition theorem is valid for A. all linear networks B. linear and symmetrical networks only C. only linear networks having no dependent sources D. linear as well as nonlinear networks

4. none of these 5. Non linear 6. Time varying 1, 5, 6 5, 6

C. D.

1, 5 1, 3, 5, 6

642. Tellegen’s theorem is applicable when A. Nature of elements is irrelevant B. Elements are linear time varying C. KVL and KCL is not satisfied D. none of these 643. Reciprocity theorem is applicable when network is 1. Linear 2. Time invariant 3. Passive 4. Independent source 5. Dependent source 6. Mutual inductors Identify the correct combination A. 1, 2, 6 C. 1, 2, 4 B. 1, 2, 3, 6 D. 1, 2, 3 644. Consider the following statements: 1. Tellegen’s theorem is applicable to any lumped networks 2. The reciprocity theorem is applicable to linear bilateral networks 3. Thevenin’s theorem is applicable to two terminal linear active networks 4. Norton’s theorem is applicable to two terminal linear active networks Which of these statements are correct? A. 1, 2 and 3 C. 1, 2 and 4 B. 1, 2, 3 and 4 D. 3 and 4 645. Match List–I with List-II and select the correct answer using the codes given below the lists: List I List II Network Theorems Most distinguished property of network A. Reciprocity 1. Impedance Matching B. Tellegen’s 2. Bilateral C. Superposition 3.∑𝑏𝑘=0 𝑉𝑗𝑘 (𝑡1 )𝐼𝑗𝑘 (𝑡2 ) = 0 D. Maximum power 4. Linear Transfer 5. Non linear CODES: CODES: ABCD ABCD A. 1 2 3 4 C. 2 3 4 1 B. 1 2 3 5 D. 2 3 5 1

640. Substitution theorem is not used in the analysis of networks in which they contain elements as A. Linear C. Time varying B. non-linear D. none of these

646. In a linear circuit the super position principle can be applied to calculate the A. Voltage and power B. voltage and current C. current and power D. voltage, current and power

641. Thevenin’s theorem is not applicable when 1. Load is coupled with the network 2. Linear 3. Time invariant

647. In applying Thevenin’s theorem, to find the Thevenin impedance, some sources (call them set S1) have to be replaced by their internal impedances, while

others (call them set S2) should be left undisturbed. A. B. C. D.

S1 consists of independent sources while S2 includes all independent sources S1 consists of dependent sources while S2 includes all independent sources S2 is a null set S1 is a null set

648. In the network shown, which one of the following theorems can be conveniently used to calculate the power consumed by the 10 ohm resistor.

A. B.

4 V, 2 Ω 4 V, 4 Ω

C. D.

8 V, 2 Ω 8 V, 4 Ω

652. A battery charger can drive a current of 5A into a 1 ohm resistance connected at its output terminals. If it is able to charge an ideal 2V battery at 7A rate, then its Thevenin’s equivalent circuit will be A. 7.5V in series with 0.5 ohm B. 12.5 V in series with 1.5 ohms C. 7.5V in parallel with 0.5 ohm D. 12.5V in parallel with 0.5 ohm 653. Find Va for which maximum power is transferred to the load.

A. B. C. D.

Thevenin’s theorem Maximum power transfer theorem Millman’s theorem Superposition theorem

649. Find the Thevenin equivalent resistance of the circuit to the left of the terminals marked a and b in the figure.

A. B.

0.2 Ω 0.4 Ω

C. D.

2Ω none of these

650. A dc current source is connected as shown in below figure. The Thevenin’s equivalent of the network at terminals a – b will be

A. B. C. D.

4 V voltage source parallel with 2 ohms resistor 4 V voltage source 2 V voltage source parallel with 2 ohms resistor none of these

651. In the network shown in the given figure current i= 0 when E = 4 V, I = 2 A and I = 1 A when E = 8 V, I = 2A. The Thevenin voltage and the resistance looking into the terminals AB are

A. B.

7.5 V 20 V

C. D.

10 V none of these

654. If the networks shown in fig. I and II are equivalent at terminals A-B, then the values of V (in volts) and Z (in ohms), will be

A. B.

V 100 60

Z 12 12

C. D.

V 100 60

Z 30 30

655. In the circuit shown, the power dissipated in 30 ohm resistor will be maximum if the value of R is

A. B.

30 ohms 16 ohms

C. D.

9 ohms zero

656. In the circuit shown, the power consumed in the resistance R is measured when one source is acting at a time. These values are 18 W, 50 W and 98 W. When all the sources are acting simultaneously, the possible maximum and minimum values of power in R will be

(b). If a variable resistance RL is connected across the terminal – pair (A, B) the maximum power that can be supplied to RL would be

A. B.

98W and 18 W 166 W and 18 W

C. D.

450 W and 2 W 166 W and 2 W

657. The value of Rx so that power dissipated in it is maximum

A. B. C. D.

80 W 40 W 20 W Indeterminate unless the actual network is given

661. In the lattice network, find the value of R for the maximum power transfer to the load.

A. B.

33.4 kohms 17.6 kohms

C. D.

10 kohms 5 kohms

658. In the circuit shown in the given figure RL will absorb maximum power when its value is

A. B.

5Ω 6.5 Ω

C. D.

8Ω 9Ω

662. In the network of the given figure, the maximum power is delivered to RL if its value is

A. B.

16 ohms 40/3 ohms

C. D.

60 ohms 20 ohms

663. Find the current I in the given figure. A. B.

2.75 Ω 7.5 Ω

C. D.

25 Ω 27 Ω

659. For the circuit shown, identify the correct statement.

A. B.

A. B. C. D.

Efficiency of power transmission is maximum when RS = RL efficiency of power transmission is maximum when RS < RL efficiency of power transmission is maximum when RS > RL none of these

660. The V-I characteristics as seen from the terminal-pair (A, B) of the network of figure (a) is shown in figure

1.5 A 2.0 A

C. D.

1.2 A –4/5 A

664. In the circuit of the given figure, the maximum power will be delivered to RL and RL equals

A. B.

6Ω 2Ω

C. D.

4/3 Ω 1Ω

665. The maximum power that can be transferred to the load resister RL from the voltage source in the figure is

A. B.

1W 10 W

C. D.

0.25 W 0.5 W

666. For the circuit shown, Thevenin’s voltage and Thevenin’s equivalent resistance at terminals a and b is

A. B. C. D.

5 V and 2 ohms 7.5 V and 2.5 ohms 4 V and 2 ohms 3 V and 2.5 ohms

R = r = 20 ohms R = r = 5 ohms R = 10 ohms; r = 5 ohms R = r = 10 ohms

20 V, 9 ohms 40 V, 19/3 ohms

672. EE Board Exam April 1990 A time of 10 milliseconds is required for the current on a series RL dc circuit to reach 90% of its final steady state value. Assume at t = 0, i(0) = 0. What is the time constant in seconds for the circuit? A. 4.25 ms C. 3.39 ms B. 3.86 ms D. 4.34 ms 673. EE Board Exam April 1995 The shunt winding of a machine has a resistance of 80 ohms and an inductance of 4 H is suddenly switched on to a 220 V supply. Find the time taken for the current to rise to half its steady state value. A. 0.0512 sec C. 0.0251 sec B. 0.0346 sec D. 0.0172 sec

668. Thevenin’s equivalent of the circuit shown in the figure: Vth, Zth values are

A. B.

670. EE Board Exam October 1980 In an RL circuit, Kirchhoff’s law gives the following relation: E = Ldi/dt + Ri where: E = supply voltage (200 volts) R = resistance (20 ohms) L = inductance (1 Henry) t = time in seconds i = current in amperes If i = 0 when t = 0, find i after a long time. A. 10 A C. 0 B. 11.2 A D. infinite 671. EE Board Exam October 1990 A 6 H coil whose resistance is 12 ohms is connected in series with a 24 ohms resistor and to a 144 V battery and a switch. The switch is closed at t = 0. Determine the time constant and the steady state current of the circuit. A. 0.36 sec, 12 A C. 0.66 sec, 3 A B. 0.45 sec, 4 A D. 0.50 sec, 6 A

667. Find the value of R and r. Thevenin’s equivalent circuit is given by circuit as shown

A. B. C. D.

i = current in amperes If i = 0 when t = 0, find i when t = 0.02 second. A. 3.3 A C. 3.2 A B. 3.1 A D. 3.0 A

C. D.

40 V, 9 ohms 40 V, 8 ohms

F. ELECTRICAL TRANSIENTS 669. EE Board Exam April 1979, October 1982 In an RL circuit, Kirchhoff’s law gives the following relation: E = Ldi/dt + Ri where: E = supply voltage (200 volts) R = resistance (20 ohms) L = inductance (1 Henry) t = time in seconds

674. EE Board Exam October 1990 A 6 H coil whose resistance is 12 ohms is connected in series with a 24 ohms resistor and to a 144 V battery and a switch. The switch is closed at t = 0. Determine the current at t = 0.1 second. A. 1.538 A C. 1.805 A B. 1.750 A D. 1.624 A 675. EE Board Exam October 1992 An uncharged capacitor in series with a 120 volt voltmeter of 10,000 ohms resistance is suddenly connected to a 100 V battery. One second later, the voltmeter reads 60 volt. Determine the capacitance of the capacitor. A. 187.54 μF C. 195.76 μF B. 190.62 μF D. 192.23 μF 676. REE Board Exam April 1999 A 20 ohm resistance R and a 0.001 farad capacitance C are in series. A direct current voltage E of 100 volts is applied across the series circuit at t

= 0 and the initial current i(0) = 5 A. Determine the resulting current i(t) at t = 0.01 second. A. 3.34 A C. 2.78 A B. 3.67 A D. 3.03 A 677. EE Board Exam October 1991 A series RC circuit consist of R = 2 MΩ and an uncharged capacitor C = 5 μF. The circuit is connected across a 100 V DC source at t = 0. Determine the voltage across the resistor 5 seconds later. A. 63.31 V C. 66.24 V B. 60.65 V D. 69.22 A 678. EE Board Exam October 1991 An uncharged capacitor in series with a 120 volt voltmeter of 10,000 ohms resistance is suddenly connected to a 100 V battery. One second later, the voltmeter reads 60 volt. Determine the rate at which the voltage across the capacitor is charging. A. 51 e-0.55t C. 55 e-0.55t B. 51 e-0.51t D. 55 e-0.51t 679. EE Board Exam October 1981 In a circuit consisting of a series resistance and capacitance and connected to a DC source, R = 20 ohms, C = 250 microfarad and E = 100 volts, find i after a long time. A. 1 A C. infinity B. 0 A D. 5 A 680. EE Board Exam April 1993 A 100 μF capacitor initially charged to 24 V is discharge across a series combination of a 1 kΩ resistor and a 200 μF capacitor. Find the current after 1 sec. A. 7.34 nA C. 8.43 nA B. 7.24 nA D. 8.84 nA 681. EE Board Exam October 1991 A series RC circuit consist of R = 2 MΩ and an uncharged capacitor C = 5 μF. The circuit is connected across a 100 V DC source at t = 0. What is the initial rate of change of voltage across the resistor? A. -10 V/s C. -12.4 V/s B. 10 V/s D. none of these 682. REE Board Exam March 1998 A 10 ohm resistance R and a 1 Henry inductance L are connected in series. An AC voltage e(t) = 100 sin 377t is applied across the connection. Solve for the particular solution (without the complementary solution) and determine the amplitude of the resulting sinusoidal current i(t). A. 0.321 A C. 0.241 A B. 0.292 A D. 0.265 A 683. EE Board Exam April 1991 A certain electric welder has a basic circuit equivalent to a series RL with R = 0.1 Ω and L = 1 mH. It is connected to an AC source “e” through a switch “s” operated by an automatic timer, which

closes the circuit at any desired point on the 60 cycle, sinusoidal wave ”e”. Calculate the magnitude of the transient current resulting when “s” closes as “e” is passing through its peak value of 100 volts. A. 256.41 A C. 80.54 A B. 65.74 A D. 76.32 A 684. REE Board Exam October 1999 A series RL circuit is connected to an AC source of 100 sin 377t. Where L = 0.1 Henry, R = 10 ohms and i(0) = 0. Determine the current at t = 0.01 second. A. 2.784 A C. 2.531 A B. 2.301 A D. 3.062 A 685. REE Board Exam April 1999 A series circuit has R = 10 ohms. L = 0.1 Henry and C = 0.0001 Farad. An AC voltage e = 100 sin 377t is applied across the series circuit. Solve for the particular solution (without the complementary solution) and determine the amplitude of the resulting sinusoidal current i(t). A. 5.51 A C. 6.67 A B. 6.06 A D. 7.34 A 686. REE Board Exam October 1999 A 10 ohm resistance R and a 0.001 Farad capacitance C are in series. An AC voltage e(t) = 100 sin 377t is applied across the series circuit. Solve for the particular solution (without the complementary solution) and determine the amplitude of the resulting sinusoidal current i(t). A. 9.67 A C. 8.79 A B. 10.63 A D. 11.70 A 687. REE Board Exam October 1999 If R = 50 ohms, C = 0.0001 Farad, E = 100 volts and i(0) = 2 amperes, determine the Laplace transform expression for I(s). A. I(s) = 2/(s + 200) C. I(s) = 2/(s + 50) B. I(s) = 2/[s(s + 2)] D. I(s) = 2/(s + 2) 688. REE March 1998 A generator has a field winding with an inductance L = 10 Henry and a resistance Rf = 0.1 ohm. To break the initial field current of 1000 amperes, the field breaker inserts a field discharge resistance Rd across the field terminals before the main contacts open. As a result, the field current decays to zero according to the differential equation. 𝑑𝑖 𝐿 + 𝑖𝑅 = 0 Where: R = Rf + Rd 𝑑𝑡 preventing a sudden decrease of i to zero, and a resulting high inductive voltage due to L. Solve the differential equation and determine the value of Rd that would limit the initial voltage across it to 1,000 volts A. 0.90 ohm C. 0.85 ohm B. 0.80 ohm D. 0.95 ohm 689. EE Board Exam April 1995 The growth of current in an inductive circuit follows A. Linear law C. Ohm’s law B. Exponential law D. Hyperbolic law

690. EE Board Exam April 1994 The time constant of an RL series circuit is A. R + L C. L/R B. R/L D. RL 691. EE Board Exam April 1998, April 1995 If a dc voltage is applied to an initially uncharged series RC circuit, the initial value of the current is A. zero C. infinite B. V/R D. CV 692. ECE Board Exam April 1999 What is the voltage drop across the resistor in an RC charging circuit when the charge on the capacitor is equal to the battery voltage? A. 0.10 volt C. zero B. 1.0 volt D. 10 volts 693. ECE Board Exam April 2000 What is the RC time constant of a series RC circuit that contains a 12 MΩ resistor and a 12 F capacitor? A. 144 seconds C. 14.4 seconds B. 1.44 seconds D. 1440 seconds 694. ECE Board Exam April 2000 What is the time constant of a 500 mH coil and a 3,300 ohm resistor in series? A. 0.0015 sec C. 1650 secs B. 6.6 secs D. 0.00015 sec 695. ECE Board Exam November 2000 In RL circuit, the time constant is the time required for the induced current to reach what percentage of its full value? A. 100% C. 37% B. 63% D. 0% 696. EE Board Exam April 1990, October 1990 A 6 H coil whose resistance is 12 ohms is connected in series with a 24 ohms resistor and to a 144 V battery and a switch. The switch is closed at t = 0. Determine the time constant of the circuit and the steady-state current. A. 0.5 sec; 6 A C. 0.1667 sec; 4 A B. 0.25 sec; 12 A D. 0.131 sec; 6 A 697. EE Board Exam October 1991 A series RC circuit consist of R = 2 MΩ and an uncharged capacitor C = 5 μF. The circuit is connected across a 100 V DC source at t = 0. Determine the voltage across the resistor at the instant the switch is closed and 5 seconds after the switched has been closed. A. 100 V, 60.65 V C. 100 V, 0 V B. 0 V, 60.65 V D. 0 V, 100 V 698. The rate of rise of current through an inductive coil is maximum A. after 1 time constant B. at the start of current flow C. near the final maximum value of current D. at 63.2% of its maximum steady state value

699. Energy stored by a coil is doubled when its current is increased by ____. A. 100% C. 50% B. 41.4% D. 25% 700. The initial current in an RL series circuit when a dc source is suddenly applied A. unity C. infinite B. V/R D. zero 701. At steady state in an RL circuit, the inductance will act as A. open circuit C. transient circuit B. short circuit D. coupled circuit 702. The rise of the current in an RL series circuit is what? A. B.

linear sinusoidal

C. D.

exponential symmetrical

703. The transient current is undamped if A. R = 0 B. [R/2L]2 > [1/(LC)] C. [R/2L]2 = [1/(LC)] D. [R/2L]2 < [1/(LC)] 704. The transient current is oscillatory if A. R = 0 B. [R/2L]2 > [1/(LC)] C. [R/2L]2 = [1/(LC)] D. [R/2L]2 < [1/(LC)] 705. The capacitor in a series RC circuit at steady state is A. B.

open circuit short circuit

C. D.

transient circuit coupled circuit

706. What is the time constant in an RC series circuit? A. C/R C. RC B. R/C D. C 707. A circuit of resistance and inductance in series has an applied voltage of 200 volts across it. What is the voltage drop across the inductance at the instance of switching? A. 200 V C. 20 V B. 0 V D. 2,000 V 708. The current in series RC circuit at steady state is A. zero C. constant B. infinite D. V/R 709. Transient disturbance is produced in a circuit whenever A. it is suddenly connected or disconnected from the supply B. it is shorted C. its applied voltage is changed suddenly D. all of the above 710. There are no transients in pure resistive circuits because they

A. B. C. D.

offer high resistance obey Ohm’s law have no stored energy are linear circuits

711. Transient currents in electrical circuit are associated with A. inductors C. resistors B. capacitors D. both A and B 712. The transients which are produced due to sudden but energetic changes from one steady state of a circuit to another are called ____ transients. A. initiation C. relaxation B. transition D. subsidence 713. In a R-L circuit connected to an alternating sinusoidal voltage, size of transient current primarily depends on A. the instant in the voltage cycle at which circuit is closed B. the peak value of steady-state current C. the circuit impedance D. the voltage frequency 714. Double-energy transients are produced in circuits consisting of A. two or more resistors B. resistance and inductance C. resistance and capacitance D. resistance, inductance and capacitance 715. The transient current in a loss-free L-C circuit when excited from an ac source is a/an ____ sine wave. A. over damped B. undamped C. under damped D. critically damped 716. Transient currents in an R-L-C circuit is oscillatory when A. 𝑅 = 0 C. 𝑹 < √𝑳/𝑪 B. 𝑅 > √𝐿/𝐶 D. 𝑅 = √𝐿/𝐶 717. A coil has a time constant of 1 second and an inductance of 8 H. If the coil is connected to a 100 V dc source, determine the rate of rise of current at the instant of switching. A. 8 amp/sec C. 0.25 amp/sec B. 12.5 amp/sec D. 0.04 amp/sec 718. A 20 ohm resistor, a 0.01 H inductor and a 100 uF capacitor are connected in series to a 200 V DC supply. The capacitor is initially uncharged. Find the maximum instantaneous current. A. 8.44 A C. 6.44 A B. 7.44 A D. 5.44 A . 719. A 10,000 ohms voltmeter connected in series with 80 F capacitor is suddenly connected to a 100 V dc source at t = 0. At what time does the voltmeter read 40 volts?

A. B.

0.654 sec 0.51 sec

C. D.

0.733 sec 0.1 sec

720. A series RLC circuit with inductance of 100 Henry has a transient resonant frequency of 5 cps. Solve the capacitance of the circuit if the effect of R on the frequency is negligible. A. 10.1 F C. 400 F B. 0.104 F D. 4 F 721. A 60 μF capacitor is connected in series with a 400 ohm resistor. If the capacitor is initially uncharged, determine the resistor and capacitor voltages when t = 1.5 times the time constant for a suddenly applied source emf of 120 volts. A. 26.78 V, 93.22 V B. 120 V, 0 V C. 93.22 V, 26.78 V D. 0 V, 120 V 722. A series RL network, with R = 2 ohms and L = 0.5 H, has an applied voltage v(t). Find the time constant for the circuit current. A. 4 sec C. 2 sec B. 0.5 sec D. 0.25 sec 723. A coil having a resistance of 10 ohms and an inductance of 4 H is switched across a 20-V dc source. Calculate the time taken by the current to reach 50% of its final steady state value. A. 151.8 V C. 88.2 V B. 189.4 V D. 101.2 V 724. A constant voltage is applied to a series RL circuit at t = 0 by closing the switch. The voltage across L is 25 volts at t = 0 and drops to 5 volts at t = 0.025 second. If L = 2 H, what must be the value of R in ohms? A. 188.30 C. 128.80 B. 1288 D. 182.80 725. A circuit whose resistance is 20 ohms and inductance of 10 H has a steady state voltage of 100 volts suddenly applied to it. For the instant of 0.50 second after the voltage is applied, determine the total power input to the circuit. A. 200 watts C. 316 watts B. 116 watts D. 500 watts 726. A circuit of resistance R ohms and inductance L Henry has a direct voltage of 230 volts applied to it. 0.30 second after switching on, the current was found to be 5 ampere. After the current had reached its final value, the circuit was suddenly shortcircuited. The current was again found to be 5 ampere at 0.30 second after short-circuiting the coil. Find the value of R and L. A. 230 Ω, 10 H C. 10 ohms. 23 H B. 23 Ω, 10 H D. 10 Ω, 32 H 727. The field winding of a separately-excited DC generator has an inductance of 60 H and a resistance of 30 ohms. The discharge resistance of

50 ohms is permanently connected in parallel with winding which is excited from a 200 volt supply. Find the value of the decay current 0.60 sec after the supply has been switched off. A. 4.94 A C. 1.12 A B. 3.67 A D. 3 A

and remains zero thereafter. This voltage is applied to an RL series circuit in which R = 5 ohms and L = 100 mH. What is the current when t = 0.50 second?

728. A 5 microfarad capacitor is discharged suddenly through a coil having an inductance of 2 H and a resistance of 200 ohms. The capacitor is initially charge to a voltage of 10 volts. Find the additional resistance required just to be prevent oscillation. A. 1625 ohms C. 1265 ohms B. 1065 ohms D. 1025 ohms

737. A capacitance of 10 microfarad is connected in series with a resistance of 8,000 ohms. If the combination is suddenly connected to a 100 V DC supply. Find the initial rate of rise in potential across the capacitor. A. 12500 V/s C. 1250 V/s B. 125 V/s D. 12.50 V/s

729. The rate of rise of current through an inductive coil is maximum A. after 1 time constant B. at the start of current flow C. near the final maximum value of current D. at 63.2% of its maximum steady state value

738. A 25 microfarad capacitor is connected in series with a 0.50 M-ohm resistor and a 120 volt storage battery. What is the potential difference in the capacitor 6 sec after the circuit is closed? A. 64 volts C. 4.60 volts B. 46 volts D. 6.40 volts

730. A coil of 15 H inductance and 10 ohms resistance is suddenly connected to a 20 volts DC source by closing the switch. The value of current 2 seconds after the switch is closed is A. 1.74 A C. 1.17 A B. 1.47 A D. 1.71 A

739. A capacitor of 2 microfarad with an initial charge q0 is connected across the terminals of a 10 ohm resistor and the switch is closed at t = 0. Find q0 (micro-coulomb) if the transient power in the resistor −5 is known to be 𝑝𝑅 = 360𝑒 −10 𝑡 A. 1200 C. 102 B. 120 D. 2100

731. A DC voltage of 80 volts is applied to a circuit containing a resistance of 80 ohms in series with an inductance of 20 Henry. Calculate the growth of current at the instant of completing the circuit. A. 4 A/s C. ½ A/s B. 2 A/s D. ¼ A/s 732. A 200 volt DC supply is suddenly switched to a relay coil which has a time constant of 3 ms. If the current in the coil reaches 0.20 ampere after 3 ms determine the steady state value of the current. A. 0.361 A C. 0.316 A B. 0.163 A D. 0.631 A 733. A relay has a resistance of 300 ohms and is switched to a 100 V DC supply. If the current reaches 63.2% of its final value at 0.02 sec, determine the inductance of the circuit. A. 5 H C. 4 H B. 6 H D. 13 H 734. Energy stored by a coil is doubled when its current is increased by ____ percent. A. 100 C. 50 B. 141.4 D. 25 735. A 60 volt potential difference is suddenly applied to a coil of inductive 60 mH and resistance 180 ohms. At what rate is it rising after 0.005 sec? A. 322 A/sec C. 22.3 A/sec B. 223 A/sec D. 32.2 A/sec 736. A voltage rise linearly form zero to 100 volts in 1 second, falls instantaneously to zero at t = 1 second

A. B.

6.90 A 96 A

C. D.

9.60 A 69 A

740. The transient current in a loss-free L-C circuit when excited from an ac source is ____ a/an sine wave . A. overdamped B. undamped C. underdamped D. critically damped 741. A series RLC circuit with R = 5 ohms, L = 0.10 H, C = 500 microfarad has a constant voltage V = 10 volts applied at t = 0. Find the resulting transient current. A. B. C. D.

0.707e-50t sin 139t 0.272e-25t sin 278t 0.720e-25t sin 139t none of these

742. A circuit consisting of 20 ohms resistor, 20 mH inductor and a 100 microfarad capacitor in series is connected to a 200 V DC supply. The capacitor is initially uncharged. Find the maximum instantaneous current. A. 6.45 A C. 8.45 A B. 7.45 A D. 9.45 A 743. A time of 10 ms is required for the current in an RL circuit to reach 90% of its final value. If R is 10 ohms, find the value of C to be inserted in series with the RL circuit so that the frequency of oscillation of the resulting current is 1000 cycles per second. A. 5.38 x 10-8 Farad B. 5.83 x 10-7 Farad C. 5.83 x 10-6 Farad D. 5.83 x 10-5 Farad

744. A series RLC circuit with R = 1 kΩ, L = 1 H and C = 6.25 μF is suddenly connected across a 24 V dc source. At t = 0, i= 0 and q = 0. Determine the current after 0.01 sec. A. 3.45 mA C. 5.40 mA B. 4.61 mA D. 5.05 mA 745. A series RLC circuit has R = 200 Ω, L = 0.1 H and a capacitor C = 10 μF. If a 100 V dc source is connected across the terminals of the series circuit at t = 0, determine the current after 1 millisecond. Assume zero initial conditions. A. 0.353 A C. 0.253 A B. 0.229 A D. 0.368 A 746. Double energy transient are produced in circuits consisting of A. two or more resistors B. resistance and inductance C. resistance and capacitance D. resistance, inductance and capacitance 747. A DC voltage source is connected across a series RLC circuit, under steady state conditions, the applied DC voltage drops entirely across the A. R only B. L only C. C only D. R & L combinations 748. Consider a DC voltage source connected to a series RC circuit. When the steady state reaches, the ratio of energy stored in the capacitor to the total energy supplied by the voltage source is equal to A. 0.362 C. 0.632 B. 0.500 D. 1.00 749. An inductor at t = 0 with initial current I0 acts as A. short C. current source B. open D. voltage source 750. An inductor L carries steady state current I0, suddenly at time t = 0 the inductor is removed from circuit and connected to a resistor R. The current through the inductor at time t is equal A. I0e-Rt/L C. I0e+Rt/L B. I0 (1-e-Rt/L) D. I0 (1-e+Rt/L) 751. Transient current in a circuit results from A. voltage applied to the circuit B. impedance of the circuit C. changes in the stored energy in inductors and capacitors D. resistance of the circuit 752. A two terminal black box contains a single element which can be R, L, C or M. As soon as the box is connected to a dc voltage source, a finite non-zero current is observed to flow through the element. The element is a/an A. resistance B. inductance

C. D.

capacitance Mutual inductance

753. In a circuit the voltage across an element is v(t) = 10 (t - 0.01)e-100t V. The circuit is A. un-damped B. under damped C. critically damped D. Over damped 754. A unit step voltage is applied at t = 0 to a series RL circuit with zero initial conditions A. It is possible for the current to be oscillatory B. The voltage across the resistor at t = 0+ is zero C. The energy stored in the inductor in the steady state is zero D. The resistor current eventually falls to zero 755. A 1 µF capacitor charged through a 2 kΩ resistor by a 10 V dc source. The initial growth of capacitor voltage will be at the rate A. 3.16 V/ms C. 6.32 V/ms B. 5.0 V/ms D. 10.0 V/ ms 756. A series R-C circuit has a capacitor with an initial voltage of 11 V. A 15 V dc source is now connected across the R-C circuit. The initial rate of change of capacitor voltage can be A. 15 Χ 0.368 / RC C. 11/RC B. 15Χ 0.632 / RC D. 4/RC 757. What is vc (o+)?

A. B.

0 V

C. D.

can’t find none of these

758. The switch K opened at t = 0 after the network has attained a steady state with the switch closed. Find vs (0+) across the switch.

A. B.

VR1/R2 V

C. D.

V + VR1/R2 0

759. The switch SPST is closed at t = 0, find d/dt i1 (0+).

A. B.

2/3 A 0

C. D.

4/3 A 1A

765. What is VL (0 +), when switch K is closed at t = 0. A. B.

0 40

C. D.

50 none of these

760. SPST is closed at t = 0.What is the time constant of the circuit?

A. B.

A. B.

26/7 7/26

C. D.

7/13 none of these

761. Given VC1 (0-) = 10 V, VC2 (0-) = 5 V find VC2 (∞) = ?

A. B.

7.5 V 0

C. D.

2V -2 V

C. D.

0 none of these

766. An impulse current 2 δ(t) A, with t in second, is made to flow through an initially relaxed 3 F capacitor. The capacitor voltage at T = 0+ is A. 6V C. 2/3 V B. 2V D. zero 767. The circuit of the given figure is initially relaxed. At t = 0+, ____.

20/3 V none of these

762. Given initial charge in C0 = 500 µC. In the steady state find charge in 1 µf capacitor?

A. B.

v =0 V i=0A

C. D.

v = 100 V i=∞

768. The time constant of the circuit shown in figure is

A. B.

50 µC 100 µC

C. D.

250 µC none of these

763. Switch K is opened at t = 0, find IL (0+).

A. B.

C(R1 +R2 ) CR1R2/(R1+R2 )

C. D.

CR1 CR2

769. If i1(t) is 5 A at t = 0, find i1(t) for all t when is(t) = 10 e2t.

A. B.

5A 0

C. D.

2A none of these

764. Given L1 = 1 H, R = 10 Ω , L2 = 2 H , iL1 (0-) = 2A. Find iL2 (∞).

A. B.

e-2t 20e-2t

C. D.

30e-2t 6.67e-2t - 1.67

770. The switch in the circuit of the figure has been closed for a long time. It is opened at t = 0.

A. B. C. D.

774. For the circuit shown different time constants are given. What are the charging and discharging times respectively? 1. 0.5 x 10-3 S 2. 2 x 10-3 S 3. 0.25 x 10-3 S 4. 10-3 S

v(0+) = 1 V, i (0+) = 0 A v(0+) = 0 V, i(0+) = 0 A v(0+) = 0 V, i (0+) =1 A v (0+) = 1 V, i(0+) = 1 A

771. In the circuit shown, the switch is moved from position A to B at time t = 0. The current i through the inductor satisfies the following conditions 1. i(0) = -8A 2. di/dt (t = 0) = 3 A/s 3. i(∞) = -4A The value of R is

A. B.

1, 2 2, 3

C. D.

1, 3 2, 4

775. A. B.

C. D.

A. B.

C. D.

A. B.

C. D.

A. B.

C. D.

A. B.

C. D.

776.

777.

A. B.

0.5 ohm 2.0 ohm

C. D.

4.0 ohm 12 ohm

772. In the circuit shown below, the switch is closed at t = 0. The current through the capacitor will decrease exponentially with a time constant

778.

779.

780. If Vs = 40t V for t > 0 and iL (0) = 5A, what is the value of i(t) at t = 2sec? A. B.

0.5 s 1s

C. D.

A. B.

2s 10s

773. In the network shown, the switch is opened at t = 0. Prior to that, network was in the steady- state, Vs (t) at t =0 is

781.

24A 34A

C. D.

A. B.

C. D.

A. B.

C. D.

A. B.

C. D.

782.

783.

A. B.

0 5V

C. D.

10V 15V 784. Consider the following units:

29A 39A

1. sec-1 2. rad2-sec-2 3. second 4. Ohm The units of R/L, 1/LC, CR and √𝐿/𝐶 are respectively ____. A. 1, 2, 4 and 3 C. 2, 4, 1 and 3 B. 3, 2, 1 and 4 D. 1, 2, 3 and 4

Question Bank in AC Circuits A. 1.

2.

3.

SINUSOIDAL VOLTAGE AND CURRENT REE Board Exam September 2000 Find the average current during the half cycle given the instantaneous maximum value of 20 amperes. A. 12.73 amperes C. 20 amperes B. 14.14 amperes D. 10 amperes REE Board Exam April 1997 The phase shift between the current and voltage vectors us due to the following except one A. magnet coils capacitors

C.

power

B. electric flat iron lamp

D.

fluorescent

REE Board Exam April 2001 An alternating rectangular wave has a maximum value of 10 V and a frequency of 1 cycle per second. What is the average value of the wave? A.

5V B.

4.

5.

0

D.

7.07 V

REE Board Exam October 2000 A sinusoidal current wave has a maximum value of 20 A. What is the average value of one-half cycle? A.

5A

C.

14.14 A

B.

12.7 A

D.

0

REE Board Exam October 1996 What is the wavelength of a carrier wave with frequency of 100 megahertz? A. B.

6.

10 V

C.

3.0 m 7.5 m

C. D.

1.5 m 6.0 m

REE Board Exam April 1997 A chart speed of a recording instrument is 25 mm/sec. One cycle of the signal being recorded extends over 5 mm. What is the frequency of the signal? A. 20 cps C. 50 cps B. 2 cps D. 5 cps

7.

EE Board Exam April 1992 Determine the rms value of the current drawn by a 2 μF condenser, which is connected across a source of potential. The potential has a third and fifth harmonic components, which are 30% and 20% respectively of the fundamental. The fundamental sinusoidal component has a peak value of 1000 volts and 60 Hz frequency. A. 0.89 A C. 0.91 A B. 0.75 A D. 0.84 A

8.

EE Board Exam April 1990 A 240-V, 25 Hz sinusoidal generator is connected to a 20 ohms resistor. Determine the instantaneous current when elapsed time is 0.01 second. A. 15.43 A C. 16.97 A B. 16.30 A D. 12.00 A

9.

REE Board Exam April 1997 A wire carries a current i = 3 cos 314t amperes. What is the average current over 6 seconds? A. B.

0A 3.0 A

C. D.

1.5 A 0.532 A

10. REE Board Exam April 1997 Across a 230-V, 60 Hz power supply is a 15ohm non-inductive resistor. What is the equation of the resulting current? A. i = 21.68 sin 377t 377t B. i = 26.56 sin 377t 120t

C.

i = 15.33 sin

D.

i = 28.16 sin

11. EE Board Exam April 1991 Determine the effective value of the circuit current of an emf of 151 sin 377t is connected in series with a DC emf of 110 volts. Both supply a load of 10 + j8 ohms. A. 10.3 A C. 13.8 A B. 12.5 A D. 11.4 A 12. EE Board Exam April 1994 An alternating current and a direct current flow simultaneously in the same conductor. If the effective of the alternating current is 5 A and the direct current is 10 A, what will an AC ammeter read when connected in the circuit? A. 7.5 A C. 11.18 A B. 15 A D. none of these 13. REE Board Exam April 1997 If e = 100 sin (ωt – 30°) – 50 cos 3ωt + 25 sin (5ωt + 150°) and i = 20 sin (ωt + 40°) + 10 sin (3ωt + 30°) – 5 sin (5ωt – 50°). Calculate the power in watts. A. 1177 C. 1043 B. 919 D. 1224 14. ECE Board Exam November 2001 It is the value of sine wave of voltage or current at one particular instant of time. A. average value C. rms value

B. effective value value

D.

instantaneous

15. ECE Board Exam November 1998 If the combination of an ac voltage and a dc voltage has an instantaneous voltage that varies through a range from -2 V to +10 V, what is the peak ac voltage of the combination? A. 10 V C. 6 V B. 16 V D. 12 V 16. ECE Board Exam April 2001 Measured in Hertz, it is the number of cycles of alternating current per second. A. frequency C. peak to peak B. period D. wavelength 17. ECE Board Exam April 2000 If an ac signal has an average voltage of 18 V, what is the rms voltage? A. 16.2 V C. 25.38 V B. 19.98 V D. 12.73 V 18. ECE Board Exam April 2000 If an ac signal has a peak voltage of 55 V, what is the average value voltage? A. 61.05 V C. 34.98 V B. 38.86 V D. 86.35 V 19. ECE Board Exam April 1999 What is the phase relationship between current and voltage in an inductor? A. in phase B. current lags voltage by 90° C. voltage lags current by 90° D. current lags voltage by 180° 20. ECE Board Exam November 1995 If sine wave voltage varies from 0 to 200 V, how much is its instantaneous voltage at 90°? A. 100 V B. minimum voltage C. 200 V D. half of its maximum voltage 21. ECE Board Exam November 2000 How many degrees are there in one complete wave cycle? A. 360 degrees C. 180 degrees B. 90 degrees D. 720 degrees 22. ECE Board Exam April 1998 When comparing rms voltage and average voltages, which of the following statement is true, assuming sine waves? A. Either the rms voltage or the average voltage might be larger. B. The average voltage is always greater than the rms voltage. C. There will always be a very large difference between the rms voltage and the average voltage.

D.

The rms voltage is always greater than the average voltage.

23. ECE Board Exam November 1999 It is the maximum instantaneous value of a varying current, voltage, or power equal to 1.414 times the effective value of a sine wave. A. rms value C. effective value B. peak to peak value D. peak value 24. ECE Board Exam November 1999 It is the description of two sine waves that are in step with each other going through their maximum and minimum points at the same time and in same direction. A. stepped sine waves B. sine waves in coordination C. phased sine waves D. sine waves in phase 25. ECE Board Exam April 1999 What is the average voltage (Eave) output of a full wave rectifier with an output of 100 volts peak? A. 63.7 volts C. 141.4 volts B. 14.14 volts D. 6.37 volts 26. ECE Board Exam November 1997 The relation of the voltage across an inductor to it current is ____ A. Lagging the current by 90 degrees B. Leading the current by 90 degrees C. In phase with the current D. Leading the current by 180 degrees 27. ECE Board Exam April 1999 If two equal frequency ac signals of exactly 5 V each are combined with one of the signals 180 degrees out of phase with the other, what will be the value of the resultant voltage? A. 2.25 V C. 0 V B. 5 V D. 10 V 28. ECE Board Exam November 1998 Kind of electric current where amplitude drops to zero periodically normally produced by rectifier circuits A. alternating current B. varying direct current C. damped alternating current D. pulsating direct current 29. ECE Board Exam April 2000 If an ac signal has an average voltage of 18 V, what is the rms voltage? A. 16.2 V C. 25.38 V B. 19.98 V D. 12.726 V 30. ECE Board Exam April 2001 In electronic circuit the current that flows over a capacitor _____. A. In phase with the voltage B. Leads the voltage by 180 degrees C. Lags the voltage by 90 degrees

D.

Leads the voltage by 90 degrees

31. Two current sources deliver current to a common load. The first source delivers a current whose equation is 25 sin 100πt amperes while the second delivers a current whose equation is 15 cos 100πt amperes. What is the rms value of the current in the load? A. 29.15 A C. 20.6 A B. 40 A D. 10 A 32. Two alternators A and B delivers 100 A and 150 A, respectively to a load. If these currents are out of phase by 30 electrical degrees, determine the total current drawn by the load. A. 201.5 A C. 215.4 A B. 250.0 A D. 241.8 A 33. When using circuit laws and rules we must use A. maximum value C. effective value B. average value D. peak to peak value 34. A 60 Hz frequency would cause an electric light to A. turn on and off 120 times per second B. flicker noticeable C. turn on and off 180 times per second D. turn on and off 60 times per second 35. The relationship between frequency f, number of revolutions per second n and pair of poles p is given by A. f = n/p C. f = n/2p B. f = np D. f = 2np 36. The difference between the peak positive value and the peak negative of an a.c. voltage is called the A. maximum value C. average value B. effective value D. peak to peak value 37. The greatest value attained during one half of the cycle is called the A. peak value C. r.m.s. value B. average value D. effective value 38. The root mean square (r.m.s.) value of a.c. is the same as A. instantaneous value C. effective value B. average value D. maximum value 39. The r.m.s. value of a sine wave is equal to A. 0.637 maximum value C. 0.707 maximum value B. 0.506 maximum value D. 1.414 maximum value 40. Form factor is defined as A. r.m.s. value/peak value B. maximum value/r.m.s. value C. r.m.s. value/average value D. effective value/ r.m.s. value

41. The value of form factor for a pure sine wave is A. 1.414 C. 0.707 B. 0.637 D. 1.11 42. The value of peak factor for a pure sine wave is A. 1.414 C. 0.707 B. 0.637 D. 1.11 43. If the current and voltage are out of phase by 90, the power is A. 1.1 VI C. Maximum B. minimum D. zero 44. If e1 = A sin t and e2 = B sin (t - ) then A. e1 lags e2 by  C. e2 lags e1 by  B. e2 leads e1 by  D. e1 leads e2 by  45. Which of the following statements concerning the graph of figure below is most correct? 3 2 1 0 time

A. B. C. D.

it represents ac it represents dc it represents half-wave rectified ac it represents sum of ac and dc

46. Average value of a sine wave is √2 times the maximum value A. True B. False 47. The equation for 25 cycles current sine wave having rms value of 30 amperes will be A. 30 sin 25t C. 30 sin 50t B. 42.4 sin 25πt D. 42.4 sin 50πt 48. The voltage v = 90 cos (ωt – 161.5°) may be represented as a sine function by A. 90 sin (ωt + 18.5°) C. 90 sin (ωt + 71.5°) B. 90 sin (ωt – 71.5°) D. 90 sin (ωt 18.5°) 49. Which of the following frequencies has the longest period? A. 1 Hz C. 1 kHz B. 10 Hz D. 100 kHz 50. RMS value and the mean value is the same in case of A. square wave B. sine wave C. triangular wave D. half-wave rectified sine wave 51. If emf in a circuit is given by e = 100 sin 628t, the maximum value of voltage and frequency are A. 100 V, 50 Hz C. 100 V, 100 Hz

B.

50√2 V, 50 Hz

D.

50√2 V, 100 Hz

52. When the sole purpose of an alternating current is to produce heat, the selection of conductor is based on A. average value of current C. rms value of current B. peak value of current D. any of the above 53. The form factor of dc supply voltage is always A. infinite C. 0.5 B. zero D. unity

ω rad/sec

Coil of N turns

φmax Figure 1.1

A. B.

max sin t max cos t

C. D.

max tan t max cot t

61. In Fig. 1.1, the maximum e.m.f. induced in the coil is ____.

54. The frequency of a sinusoidal signal shown in figure is

ω rad/sec

Coil of N turns

φmax Figure 1.1

A. B. A. B.

500 Hz 1 kHz

C. D.

25 kHz 500 kHz

55. The period of the voltage 2 cos 4500πt + 7 sin 7500πt is A. 2.51 s C. 2.51 ms B. 2.51 ns D. 2.51 μs 56. The a.c. system is preferred to d.c. system because ____ A. a.c. voltages can easily be changed in magnitude B. d.c. motors do not have fine speed control C. high-voltage a.c. transmissions is less efficient D. d.c. voltage cannot be used for domestic appliances 57. In a.c. system, we generate sine wave form because ____ A. it can be easily drawn B. it produces lest disturbance in electrical circuits C. it is nature’s standard D. other waves cannot be produced easily 58. ____ will work only on d.c. supply. A. Electric lamp C. Heater B. Refrigerator D. Electroplating 59. ____ will produce a.c. voltage. A. Friction C. B. Photoelectric effect D.

Thermal energy Crystal

60. In Fig. 1.1, the component of flux that will contribute to e.m.f. in the coil is ____

N max  max

C. D.

N max sin t  N max

62. A coil is rotating in the uniform field of an 8-pole generator. In one revolution of the coil, the number of cycles generated by the voltage is ____. A. one C. four B. two D. eight 63. An alternating voltage is given by v = 20 sin 157t. The frequency of the alternating voltage is ____. A. 50 Hz C. 100 Hz B. 25 Hz D. 75 Hz 64. An alternating current is given by i = 10 sin 314t. The time taken to generate two cycles of current is ____. A. 0.02 second C. 0.04 second B. 0.01 second D. 0.05 second 65. An alternating voltage is given by v = 30 sin 314t. The time taken by the voltage to reach –30 V for the first time is ____. A. 0.02 second C. 0.03 second B. 0.1 second D. 0.015 second 66. A sine wave has a maximum value of 20 V. Its value at 135 is ____. A. 10 V C. 15 V B. 14.14 V D. 5 V 67. A sinusoidal current has a magnitude of 3 A at 120. Its maximum value will be ____. A. √3 A C. 𝟐√𝟑 A B. √3/2 A D. 6 A 68. An alternating current given by i = 10 sin 314t. Measuring time from t = 0, the time taken by the current to reach +10 A for the second time is ____. A. 0.05 second C. 0.025 second B. 0.1 second D. 0.02 second

69. An a.c. generator having 10 poles and running at 600 r.p.m. will generate an alternating voltage of frequency _____ A. 25 Hz C. 50 Hz B. 100 Hz D. 200 Hz 70. We have assigned a frequency of 50 Hz to power system because it ____ A. can easily be obtained B. gives best result when used for operating both lights and machinery C. leads to easy calculation D. none of the above 71. An alternating voltage is given by v = 100 sin 314t volts. Its average value will be ____. A. 70.7 V C. 63.7 V B. 50 V D. 100 V 72. An alternating current whose average value is 1 A will produce ____ 1 A d.c. under similar conditions. A. less heat than C. the same heat as B. more heat than D. none of the above 73. A sinusoidal alternating current has a maximum value of Im. Its average value will be ____. A. Im/ C. 2Im/ B. Im/2 D. none of the above 74. The area of a sinusoidal wave over a half-cycle is ____ A. max. value / 2 C. max. value /  B. 2 x max. value D. max. value / 2 75. An alternating voltage is given by v = 200 sin 314t. Its r.m.s. value will be ____ A. 100 V C. 141.4 V B. 282.8 V D. 121.4 V 76. The r.m.s. value of sinusoidally varying current is ____ that of its average value. A. more than C. same as B. less than D. none of the above 77. Alternating voltages and currents are expresses in r.m.s. values because ____ A. they can be easily determined B. calculations become very simple C. they give comparison with d.c. D. none of the above 78. The average value of sin2 over a complete cycle is ____ A. +1 C. ½ B. -1 D. zero 79. The average value of sin over a complete cycle is ____. A. zero C. -1

B.

+1

D.

½

80. An alternating current is given by i = Im sin . The average value of squared wave of this current over a complete cycle is ____ A. Im/2 C. 2Im/ B. Im/ D. 2Im 81. The form factor a sinusoidal wave is ____ A. 1.414 C. 2 B. 1.11 D. 1.5 82. The filament of a vacuum tube requires 0.4 A d.c. to heat it. The r.m.s. value of a.c. required is ____. A. 0.4 x √2 C. 0.8 / √2 B. 0.4 / 2 A D. 0.4 A 83. A 100 V peak a.c. is as effective as ____ d.c. A. 100 V C. 70.7 V B. 50 V D. none of above

the

84. The form factor of a ____ wave is 1. A. sinusoidal C. triangular B. square D. saw tooth 85. Out of the following ____ wave is the peakiest. A. sinusoidal C. rectangular B. square D. triangular 86. The peak factor of a sine wave form is ____. A. 1.11 C. 2 B. 1.414 D. 1.5 87. When a 15-V square wave is connected across a 50V a.c. voltmeter, it will read ____. A. 15 V C. 15 /√2 B. 15 x √2 D. none of the above 88. The breakdown voltage of an insulation depends upon ____ value of alternating voltage. A. average C. peak B. r.m.s. D. twice the r.m.s. 89. The peak factor of a half-wave rectified a.c. is ____. A. 1.57 C. 1.11 B. 2 D. 1.4142 90. The form factor of a half-wave rectified a.c. is ____ A. 2 C. 1.414 B. 1.11 D. 1.57 91. When 200 V sinusoidal peak-to-peak is connected across an a.c. voltmeter, it will read ____ A. 141.4 V C. 70.7 V B. 50 V D. none of the above 92. In Fig. 1.2, the wave that will produce maximum heat under the similar conditions is ____.

i 10 A

i

i

10 A

0

0

t

v

φ

t

θ

-10 A

-10 A

Figure 1.3

i 10 A

A. a resistive B. a capacitive above

i 10 A

0

0

t

-10 A

Figure 1.2

A. B.

square wave sinusoidal wave

C. D.

triangular wave saw tooth wave

93. In Fig. 1.2, ____ wave will have the highest average value. i 10 A 0

i 10 A 0

t

t

-10 A

-10 A

i 10 A

0

t

-10 A

Figure 1.2

A. B.

an inductive none of the

98. An alternating voltage or current is a ____. A. scalar quantity C. phasor B. vector quantity D. none of above

the

99. Three parallel circuits take the following currents: i1 = 5 sin 314t, i2 = 30 sin (314t + /2) and i3 = 25 sin (314t - /2). The expression for the resultant current is ____. A. 25 sin (314t + /3) C. 10 sin (314t /6) B. 5 sin (314t + /2) D. 5√𝟐 sin (314t + /4) 100. The sum of the following two e.m.f’s will be ____ e1 = 10 sin t e2 = 10 cos t A. 10 C. 14.14 cos t B. 20 sin t D. 14.14 sin (t + /4)

i 10 A

0

C. D.

saw tooth square

C. D.

triangular sinusoidal

94. The average value of a sinusoidal current is 100 A. Its r.m.s value is ____. A. 63.7 A C. 141.4 A B. 70.7 A D. 111 A

101. Each of the three coils generates an e.m.f. of 230 V. The e.m.f. of second leads that of the first 120 and the third lags behind the first by the same angle. The resultant e.m.f. across the series combination of the coils is ____. A. 0 V C. 690 V B. 230 V D. none of the above 102. In Fig. 1.4, I1 + I2 is equal to ____

95. A current wave is given by i = 4 + 2√2sin 3 + 4√2sin 5. The r.m.s. value of current wave is ____. A. 10 A C. √𝟓𝟔 A B. 6 A D. 5 A

I2

60° 6A

I3

3A

I1

4A

Figure 1.4

96. In Fig. 1.3, current is given by i = Im sin . The voltage equation will be ____. i

v

A. B.

3A 4.33 A

C. D.

9A 3.43 A

103. In Fig. 1.4, I2 + I3 is equal to ____

φ

θ

60° 6A

I1

I2 3A

I3 4A

Figure 1.3

A. B.

Vm sin  Vm sin ( + )

C. D.

Vm sin ( - ) Vm sin ( - 2)

97. The waveforms of voltage and current shown in Fig. 1.3 would exist in ____ circuit.

Figure 1.4

A. 7 A B. √13 A above

C. D.

5A none

104. In Fig. 1.5, E1 + E2 + E3 + E4 is equal to

of

the

112. An alternating voltage v = Vm sin θ is applied to a pure capacitive circuit. The current equation will be A. i = Im sin θ C. i = Im sin(θ + π⁄4) B. i = Im sin(θ − π⁄2) D. 𝐢 = 𝐈𝐦 𝐬𝐢𝐧(𝛉 + 𝛑⁄𝟐)

E1 = 9 V E3 = 20 V E2 = 24 V E4 = 6 V Figure 1.5

A. 7 V B. 5 V above

C. D.

20 V none

of

the

105. In Fig. 1.5, ____ will have the least value. E1 = 9 V E3 = 20 V E2 = 24 V E4 = 6 V Figure 1.5

A. B.

E1 + E2 + E3 + E4 E1 + E2 + E3 – E4

C. D.

E1 + E2 - E3 – E4 -E1 + E4

106. In a pure resistive a.c. circuit, the frequency of power curve is ____ that of the circuit frequency. A. half C. thrice B. twice D. same as 107. In a pure resistive circuit, the instantaneous voltage and current are given by: v = 250 sin 314t volts i = 10 sin 314t amperes The peak power in the circuit is A. 1250 W C. 2500 W B. 25 W D. 250 W 108. In a pure resistive circuit, the instantaneous voltage and current are given by: v = 250 sin 314t volts i = 10 sin 314t amperes The average power in the circuit is A. 2500 W C. 25 W B. 250 W D. 1250 W 109. An alternating voltage v = Vm sin θ is applied to a pure inductive circuit. The current equation will be A. i = Im sin θ C. i = Im sin(θ + 𝜋 ⁄2) B. 𝐢 = 𝐈𝐦 𝐬𝐢𝐧(𝛉 − 𝝅⁄𝟐) D. i = Im sin(θ + 𝜋 ⁄4) 110. The inductive reactance of a circuit is ____ frequency. A. directly proportional to C. independent of B. inversely proportional D. none of the above 111. Power absorbed in a pure inductive circuit is zero because A. reactive component of current is zero B. active component of current is maximum C. power factor of the circuit is zero D. reactive and active component of current cancel out

113. The capacitive reactance of a circuit is ____ frequency. A. independent of B. inversely proportional to C. directly proportional to D. none of the above 114. An a.c. current given by i = 14.14 sin (t + /6) has an rms value of ____ amperes and a phase of ____ degrees. A. 10, 30 C. 1.96 , -30 B. 14.14, 180 D. 7.07, 210 115. If e1 = A sin t and e2 = B sin (t – ), then A. e1 legs e2, by  C. e2 leads e1, by  B. e2 lags e1 by  D. e1 is in phase with e2 116. From the two voltage equations eA = Em sin 100t and eB = Em sin (100t + /6), it is obvious that A. eA leads eB 30 B. eB achieves its maximum value 1/600 second before eA does C. eB lags behind eA D. eA achieves its zero value 1/ 600 before eB 117. The r.m.s. value a half-wave rectified current is 10 A, its value for full wave rectification would be ____ amperes. A. 20 C. 20/π B. 14.14 D. 40/ 118. A resultant current is made of two components: a 10 A d.c. components and a sinusoidal component of maximum value 14.14 A. The average value of the resultant current is ____ amperes and r.m.s. value is ____ amperes. A. 0, 10 C. 10, 14.14 B. 24, 24.14 D. 4.14, 100 119. The r.m.s. value of sinusoidal ac current is equal to its value at an angle of ____ degree. A. 60 C. 30 B. 45 D. 90 120. Two sinusoidal currents are given by the equations: i1 = 10 sin (t + /3) and i2 = 15 sin (t - /4). The phase difference between them is ____ degrees. A. 105 C. 15 B. 75 D. 60 121. A sine wave has a frequency of 50 Hz. Its angular frequency is ____ radian/second. A. 50/ C. 50π B. 50/2 D. 100

122. An a.c. current is given by i = 100 sin 100. It will achieve a value of 50 A after ____ second. A. 1/600 C. 1/1800 B. 1/300 D. 1/900

131. The rms value of the periodic waveform given in the figure is 6A T/2

123. The reactance offered by a capacitor to alternating current of frequency 50 Hz is 10 . If frequency is increased to 100 Hz reactance becomes ____ ohm. A. 20 C. 2.5 B. 5 D. 40 124. A complex current wave is given by i = 5 + 5 sin 100t ampere. Its average value is ____ ampere. A. 10 C. √50 B. 0 D. 5 125. The current through a resistor has a wave form as shown in Fig. 1.6. The reading shown by a moving coil ammeter will be ____ ampere. 5A i(t)

0

π

2π

3π

ωt

C. D.

5/√2 2.5/√2

-6 A

A. B.

𝟐√𝟔 A 6√2 A

C. D.

√4/3 A 1.5 A

132. If i1 = 120 cos (100πt + 30°) and i1 = -0.1 cos (100πt + 100°) then i2 leads i1 by ____. A. -110 degrees C. -60 degrees B. 60 degrees D. 110 degrees 133. If v1 = sin (ωt + 30°) and v2 = -5 sin (ωt - 15°) then v1 leads v2 by ____. A. 225 degrees C. 45 degrees B. 30 degrees D. none of the above 134. The rms value of a rectangular wave of period T, having a value of +V for a duration, T1 ( XL B. R = 0 D. XC < XL

304. In an R-L series circuit the power factor is A. leading C. zero B. lagging D. unity 305. When a sinusoidal voltage is applied across an R-L series circuit having R = XL, the phase angle will be A. 90° C. 45° leading B. 45° lagging D. 90° leading 306. An ac source having voltage e = 110 sin (ωt + π/3) is connected in an ac circuit. If the current drawn from the circuit varies as i = 5 sin (ωt - π/3) the impedance of the circuit will be A. 22 Ω C. 30.8 Ω B. 16 Ω D. none of these 307. Which are of the following true of the circuit shown in the given figure? 100 Ω

296. In an a.c. circuit, the ratio of kW/kVA represents A. power factor C. form factor B. load factor D. diversity factor 297. If p.f. of a circuit is unity, its reactive power is A. a maximum C. zero B. equal to I²R D. a negative quantity 298. An R-L-C circuit has R = 10 Ω, XL = 20 Ω and XC = 30 Ω. The impedance of the circuit is given by the expression. A. Z = 10 + j20 C. Z = 10 – j20 B. Z = 10 + j50 D. Z = -10 + j20 299. An alternating voltage e = 200 sin 314t is applied to a device which offers an ohmic resistance of 20 Ω to the flow of current in one direction while entirely preventing the flow in the opposite direction. The average value of current will be A. 5 A C. 1.57 A B. 3.18 A D. 1.10 A

150 V L

VR

+

250 2 sin300 t

-

I

1. VR = 100√2 V 2. I = 2 A 3. L = 0.25 H Select the correct answer using the codes given below: Codes: A. 2 and 3 C. 1 and 3 B. 1 and 2 D. 1, 2 and 3 308. The R-L circuit of the figure is fed from a constant magnitude variable frequency sinusoidal voltage source vin. At 100 Hz, the R and L element each has a voltage drop Vrms. If the frequency of the source is changes to 50 Hz, then new voltage drop across R is R

L

+ vin

300. A 10 mH inductor carries a sinusoidal current of 1 A rms at a frequency of 50 Hz. The average power dissipated by the inductor is A. 0 W C. 0.5 W B. 0.25 W D. 1.0 W 301. A circuit component that opposes the change in circuit voltage is A. resistance C. inductance B. capacitance D. all of the above 302. Power loss in an electrical circuit can take place in A. inductance only B. capacitance only C. inductance and resistance D. resistance only 303. A circuit of zero lagging power factor behaves as A. an inductive circuit C. R-L circuit B. a capacitive circuit D. R-C circuit

-

A. B.

√5/8 Vrms √2/3 Vrms

C. D.

√𝟖/𝟓 Vrms √3/2 Vrms

309. An ac source of 200 Vrms supplies active power of 600 W and reactive power of 800 VAR. The rms current drawn from the source is A. 10 A C. 3.75 A B. 5 A D. 2.5 A 310. A square wave is fed to an R-C circuit. Then A. voltage across R is square and across C is not square B. voltage across C is square and across R is not square C. voltage across both R and C is square D. voltage across both R and C is not square

311. The voltage phasor of a circuit is 10∠15° V and the current phasor is 2∠ − 45° A. The active and reactive powers in the circuit are A. 10 W and 17.32 VAR B. 5 W and 8.66 VAR C. 20 W and 60 VAR D. 20√2 W and 10√2 VAR 312. In a two-element series circuit, the applied voltage and resultant current are respectively, v(t) = 50 + 50 sin (5 x 103t) and i(t) = 11.2 sin (5 x 103t + 63.4°). The nature of the elements would be A. R-L C. L-C B. R-C D. neither R, nor L, nor C 313. A series circuit passive elements has the following current and applied voltage: v = 200 sin (2,000t + 50°), i = 4 cos (2,000t + 13.2°) The circuit elements A. must be resistance and capacitance B. must be resistance and inductance C. must be inductance, capacitance and resistance D. could be either resistance and capacitance or resistance, inductance and capacitance 314. A two terminal black box contains one of the R-L-C elements. The black box is connected to a 220 V ac supply. The current through the source is I. When a capacitance of 0.1 F is inserted in series between the source and the box, the current through the source is 2I. The element is A. a resistance B. an inductance C. a capacitance D. it is not possible to determine the element 315. In the following circuit, i(t) under steady state is 1Ω

2H

317. In the circuit shown in the given figure, if the power consumed by the 5 Ω resistor is 10 W, then the pf of the circuit is

50 cos ωt

A. B.

0.8 0.6

C. D.

319. If a series RLC circuit excited by a voltage e = E sin ωt when LC < 1/ω2 A. current lags behind the applied voltage B. current leads the applied voltage C. current is in phase with the applied voltage D. voltage across L and C are equal 320. The current in the circuit shown is

A. B.

5A 10 A

C. D.

15 A 25 A

L

C

i(t)

zero 5

C. D.

7.07 sin t 7.07 sin (t – 45°)

316. The source in the circuit is a sinusoidal source. The supply voltages across various elements are marked in the figure. The input voltage is 3V

0.5 zero

318. In an RL circuit, supplied from an ac source, the reactive power is proportional to the A. the average energy stored in the electric field B. the average energy stored in the magnetic field C. sum of the average energy stored in the electric field and that stored in the magnetic field D. difference of the average energy stored in the electric field and that stored in the magnetic field

R

A. B.

10 Ω

321. In the case of the R-L-C circuit shown in the given figure, the voltage across the R, L and C would be respectively

1F

5V 10 sin t

L

5Ω

14 V

15 V (rms)

A. B. C. D.

V1 20 V (rms)

V2 9 V (rms)

12 V, 16 V and 7 V or 25 V 16 V, 12 V and 7 V or 25 V 7 V, 16 V and 12 V 16 V, 12 V and 25 V

10 V

322. Consider the following statements regarding the circuit shown in the figure. 5Ω

A. B.

10 V 5V

C. D.

27 V 24 V

j15 / 3

10 Ω

10 6 V I

If the power consumed by 5 Ω resistor is 10 W then

1. |I| = √2 A 2. the total impedance of the circuit is 5 Ω 3. cos θ = 0.866 Which of these statements is correct? A. 1 and 3 C. 1 and 2 B. 2 and 3 D. 1, 2 and 3 323. In an ac circuit if voltage V = (a + jb) and current I = (c + jd), then the power is given by A. ac + ad C. bc - ad B. ac + bd D. bc + ad 324. The reactive power drawn from the source in the network in the given figure is 3Ω

-j10 Ω

+j10 Ω

10010 V

A. B.

300 VAR 200 VAR

C. D.

100 VAR zero

325. A series R-L-C circuit, consisting of R = 10 Ω, XL = 20 Ω, XC = 20 Ω is connected across an ac supply of 100 V (rms). The magnitude and phase angle (with reference to supply voltage) of the voltage across the inductive coil are respectively A. 100 V, 90° C. 200 V, -90° B. 100 V, -90° D. 200 V, 90° 326. For a capacitor in a sine wave ac circuit A. vC lags iC by 90° B. iC leads vC by 90° C. iC and vC have the same frequency D. all of the above 327. In a series RC circuit, A. VC leads VR by 90° 90° B. VC and I are in phase

C.

VC lags VR by

D.

both B and C

328. In a series RC circuit, A. VC and VR are in phase B. VT and I are always in phase C. VR and I are in phase D. VR leads I by 90° 329. When the frequency of the applied voltage increases in a series RC circuit A. the phase angle, θT, becomes more negative B. ZT increases C. ZT decreases D. both A and 330. Inductive reactance, XL A. applies only to non-sinusoidal waveforms or dc B. applies only to sine waves C. applies to either sinusoidal or non-sinusoidal waveforms D. is inversely proportional to frequency 331. For an inductor in a sine wave ac circuit

A. VT leads iL by 90° phase B. VT lags iL by 90° above 332. In a series RL circuit, A. VT lags VR by 90° phase B. VT leads VR by 90°

C.

VT and iL are in

D.

none

C.

VR and I are in

D.

both B and C

of

the

333. In a series RL circuit where XL = R, the phase angle, θZ, is A. -45° C. 90° B. 0° D. 45° 334. In an ac circuit with only series resistances A. VT and I are in phase B. RT =R1 + R2 + R3 + … + etc. C. each voltage drop is in phase with the series current D. all of the above 335. The unit of apparent power is the A. volt-ampere (VA) B. watt (W) C. volt-ampere-reactive (VAR) D. joule (J) 336. In an ac circuit with only series capacitors A. VT leads I by 90° B. VT lags I by 90° C. each capacitor voltage drop leads I by 90° D. both A and C 337. The unit of real power is the A. watt (W) B. volt-ampere (VA) C. joule (J) D. volt-ampere-reactive (VAR) 338. In a series RLC circuit A. XL and XC are 180° out of phase B. IL and IC are 180° out of phase C. XL and XC are 90° out of phase D. XL and XC are in phase 339. The power factor of an ordinary electric bulb is A. zero B. unity C. slightly more than unity D. slightly less than unity 340. The power factor of an ac circuit is equal to A. cosine of the phase angle B. sine of the phase angle C. unity for a resistive circuit D. unity for a reactive circuit 341. If f(t) = sin t + sin √2 t is passing through R = 1 ohm, what is the power dissipated in 1 ohm resistor? A. 1 W B. 2 W

C. since f(t) in non-periodic, not possible to find power D. none of the above C. PARALLEL CIRCUITS 342. EE Board Exam October 1981 A circuit consists of XL = j5 ohms, XC = -j5 ohms and R = 5 ohms all are connected in parallel. Find the equivalent impedance. A. 5.5 Ω C. 4.8 Ω B. 5.0 Ω D. 5.2 Ω 343. EE Board Exam October 1985 Given: Z1 = -j2.5 ohms; Z2 = j4 ohms; Z3 = 5 ohms; Z4 = 1 + j5 ohms. If the four impedances are connected in parallel, find the equivalent impedance in ohms. A.

4.1 + j0.72

C.

4.2 + j0.35

B.

4.3 + j0.45

D.

4.0 + j0.97

344. EE Board Exam April 1984, April 1987 Three impedances Za = 3 + j4 ohms, Zc = 4 – j4 ohms and Zc = j3 ohms are connected in parallel. Solve for the pf of the combination. A. 0.653 leading C. 0.503 leading B. 0.554 lagging D. 0.620 lagging 345. EE Board Exam October 1993 A pure capacitance of 530.515 x 10-6 farad and an inductance of 530.515 x 10-4 Henry are connected in parallel across an ac power source. Solve for the resultant impedance assuming that the frequency is 30 Hz. A. 10 Ω C. zero B. infinite D. undefined 346. REE Board Exam March 1998 A coil of a 50-ohm resistance and of 150 mH inductance is connected in parallel with a 50 μF capacitor. What is the power factor of the circuit? A. 80% C. 70% B. 50% D. 60% 347. EE Board Exam April 1982 Three impedances Za, Zb and Zc are connected in parallel. If at 60 Hz, Za = j8, Zb = -j2 and Zc = 5 ohms. Solve for the resultant power factor. A. B.

0.471 lagging 0.471 leading

C. D.

0.573 lagging 0.573 leading

348. REE Board Exam October 1997 A resistor of 50 ohms and an impedance of 100 + j50 ohms are connected in parallel across a 220 volts supply. What is the power factor of the load? A. 96% C. 98% B. 99% D. 95% 349. EE Board Exam October 1992

A capacitor of 3.18 microfarads is connected in parallel with a resistance of 2,000 ohms. The combination is further connected in series with an inductance of 795 mH and resistance of 100 ohms across a supply given by e = 400 sin wt + 80 sin (3wt + 60°). Assume w = 314 radians/sec. Determine the power dissipated. A. 74.66 W C. 80.28 W B. 78.05 W D. 75.66 W 350. EE Board Exam October 1992 A capacitor of 3.18 microfarads is connected in parallel with a resistance of 2,000 ohms. The combination is further connected in series with an inductance of 795 mH and resistance of 100 ohms across a supply given by e = 400 sin wt + 80 sin (3wt + 60°). Assume w = 314 radians/sec. Determine the circuit power factor. A. 0.702 C. 0.633 B. 0.650 D. 0.612 351. EE Board Exam April 1990 A capacitor, an electric resistance heater, and impedance are connected in parallel to a 120 V, 60 Hz system. The capacitor draws 50 var, the heater draws 100 W and the impedance coil draws 269 VA at a pf 0f 0.74 lagging. Determine the system power factor. A. 0.933 leading C. 0.916 lagging B.

0.928 lagging

D.

0.911 lagging

352. REE Board Exam October 1996 A bank of capacitors is connected in parallel each rated at 10 kVAR, 380 volts. If one unit is shorted out, what would be the net capacitance of the bank? A. 330 μF C. 220 μF B. 440 μF D. 110 μF 353. EE Board Exam October 1992 A capacitor of 3.18 microfarads is connected in parallel with a resistance of 2,000 ohms. The combination is further connected in series with an inductance of 795 mH and resistance of 100 ohms across a supply given by e = 400 sin wt + 80 sin (3wt + 60°). Assume w = 314 radians/sec. Determine the rms value of the total current. A. 0.40 A C. 0.56 A B. 0.33 A D. 0.45 A 354. EE Board Exam June 1990 Three loads, units A, B and C are connected in parallel and take currents that are respectively 12, 10 and 15 A respectively. Assuming Ia to be the reference phasor. Ib leads Ia by 30° and Ic lags behind Ia by 65°, calculate the total (resultant) current. A. B.

28.33 A 30.21 A

C. D.

26.46 A 32.10 A

355. EE Board Exam April 1992 Two single-phase motors are connected in parallel across a 120-volt, 60-cycle source of

supply. Motor A is a split-phase inductance type and motor B is a capacitor type: Motor A B

HP Output ¼ ½

Determine total power factor. A. 0.886 lag B. 0.864 lag

Efficiency 0.60 0.70

C. D.

pf 0.70 lag 0.95 lag

0.817 lag 0.825 lag

356. EE Board Exam April 1992 A 250 V, 30 Hz generator supplies power to a parallel circuit consisting of a 20 HP motor whose efficiency is 90% at 0.80 pf lagging and a second load that draws an apparent power of 7 kVA at unity pf. Determine the system power factor. A. 0.828 lagging C. 0.802 lagging B. 0.831 lagging D. 0.884 lagging 357. EE Board Exam April 1985 A resistance of 5 ohms is connected in series with a capacitor of 442.1 μF. The combination is then connected in parallel with an inductance of 21.22 mH. Solve for the resultant current if the circuit is connected across a 120 V, 60 Hz ac source. A. 9.44 A C. 11.29 A B. 10.68 A D. 10.34 A 358. EE Board Exam April 1993 An inductor L1 is connected in series with a parallel combination of inductor L2 and capacitor C. The impedance of the circuit w = 400 rad/sec is j100 ohms. The circuit is to yield infinite impedance at w = 1,000 rad/sec and zero impedance at w = 2,000 rad/sec. Determine the value of C. A. 1.28 μF C. 2.06 μF B. 1.67 μF D. 1.32 μF 359. EE Board Exam April 1992 A sinusoidal current source, 10 cos 1000t, is in parallel both with a 20-ohm resistor and the series combination of a 10-ohm resistor and a 10-mH inductor. Find the equation of the voltage across the 10-ohm resistor. A. 63.25 cos (1000t – 18.43°) B.

61.32 cos (1000t – 20.34°)

C.

59.36 cos (1000t – 17.45°)

D.

60.12 cos (1000t – 19.38°)

360. EE Board Exam April 1993 A 1-hp, 220 V, 60 Hz capacitor-start motor has main and auxiliary winding impedance at starting of 3.5 + j2.5 ohms and 8.6 + j2.5 ohms, respectively. Determine the value of the starting capacitance that will place the main and auxiliary winding currents 90 apart at starting, A. 186.75 μF C. 182.43 μF B. 174.35 μF D. 170.67 μF

361. EE Board Exam October 1990 Two impedances A and B are connected in parallel across a 120 V ac supply. The total current and the current in each impedance is adjusted to 20 A. The power drawn by A is doubled that of B and the power factor is lagging. Determine the power factor of A. A. 0.650 lagging C. 0.841 lagging B. 0.704 lagging D. 0.677 lagging 362. REE Board Exam March 1998 A coil of 50-ohm resistance and of 150-mH inductance is connected in parallel with a 50-μF capacitor. If the source voltage is 100 sin (ωt + 30°), what is the equation of the line current? A.

1.91 sin (ωt + 52.5°)

C.

1.82 sin (ωt -

B. 75.5°)

1.25 sin (ωt + 75.5°)

D.

1.32 sin (ωt –

62°)

363. EE Board Exam October 1984 A resistor R is connected in parallel with a 10ohm inductive reactance. The combination is then connected in series with a 4-ohm capacitive reactance. The whole combination is connected across a 100-volt, 60 Hz supply, How much is R if the angle between the supply voltage and the total current is 45 degrees? A.

12 ohms

C.

16 ohms

B.

25 ohms

D.

20 ohms

364. EE Board Exam April 1980 Three impedances Z1 = 1 - j4 ohms, Z2 = – j6 ohms and Z3 = 4 + j3 ohms are connected in series-parallel. Z1 is connected in series with the parallel combination of Z2 and Z3. Determine the equivalent impedance of the combination. A. 4.32 – j1.21 ohms C. 6.76 – j5.68 ohms B. 2.23 – j3.32 ohms ohms

D.

5.42 – j7.21

365. EE Board Exam October 1984 A 5-ohm resistor is connected in parallel with a 10-ohm inductive reactance. The combination is then connected in series with a 4-ohm capacitive reactance. The whole combination is connected across a 100-volt, 60 Hz supply. How much is the total current drawn by the circuit? A.

22.36 A

C.

23.16 A

B.

20.45 A

D.

19.89 A

366. EE Board Exam April 1983

A non-inductive resistor R is connected in parallel with an inductive reactance of 10 ohms. The combination is then connected in series with a capacitive reactance of 5 ohms. The whole combination is connected across a 100-volt, 60 Hz ac source. If R is equal to 5 ohms, solve for the voltage across the parallel combination. A.

87.53 V

C.

89.44 V

B.

88.34 V

D.

91.87 V

367. EE Board Exam April 1980 Three impedances Z1 = 1 - j4 ohms, Z2 = – j6 ohms and Z3 = 4 + j3 ohms respectively are connected in series-parallel. Z1 is connected in series with the parallel combination of Z2 and Z3. If this circuit is connected across a 230 V, 60 Hz source, determine the voltage across the parallel combination of Z2 and Z3. A. 156.3 V C. 135.7 V B.

146.8 V

D.

163.2 V

368. EE Board Exam October 1980 Given three impedances: Z1 = 10 + j0 ohms, Z2 = 3 + j4 ohms and Z3 = 8 – j6 ohms. Impedance Z2 and Z3 are connected in parallel and the combination is connected in series with impedance Z1 across a 120 V single-phase 60 Hz source. Find the total power drawn by the impedance. A. 1008 W C. 1038 W B.

1204 W

D.

-0.06 0.06

C. D.

0.08 -0.08

370. EE October 1986, April 1993 A parallel circuit consists of a resistor having a conductance of 4 mhos, an inductive reactor having a susceptance of 8 mhos and a capacitive reactor having a susceptance of 5 mhos. What is the impedance of the circuit? A. 0.11 + j0.13 ohms ohms B. 0.13 + j0.11 ohms ohms

373. ECE Board Exam November 2001 What is the impedance relationship between the output of one circuit and the input of another circuit will provide maximum power transfer? A. very low impedance C. lower impedance B. higher impedance D. equal impedance 374. The series circuit of R = 30 Ω & X = 4 Ω and a parallel circuit of R’ and X’ have the same impedance and power factor. Calculate the value of R’ and X’. A. 8.33 Ω and 6.25 Ω C. 7.47 Ω and 7.51 Ω B. 2.56 Ω and, 3.83 Ω D. 5.62 Ω and 9.84 Ω 375. A 25 Ω resistor, 2 mH inductor and 30 μF capacitor are connected in parallel across 100 sin (5000t + 45°) V source. Calculate the total current taken by the circuit. A. 4 sin (5000t + 45°) + 5 cos (5000t + 45°) B. 14 sin (5000t) + 15 sin (5000t + 45°) C. 40 sin (5000t + 30°) + 50 cos (5000t + 45°) D. 4 cos (5000t + 45°) + 5 cos (5000t + 45°) 376. A parallel circuit with one branch of R = 5 Ω and a single unknown element in the other branch has the following applied voltage and total current e = 10 cos (50t + 60°) V and i = 5.38 cos (50t – 8.23°) A. The unknown element is ____. A. L = 0.04 H C. C = 10 μF B. L = 0.02 H D. C = 5 μF

1103 W

369. EE Board Exam October 1993 If admittance Y = 0.06 – j0.08 mho, then conductance G equals A. B.

372. ECE Board Exam November 2000 A parallel-LC circuit can store energy fed to it power source and produces an output which is a continuous A.C. wave. It is often called a ____. A. Tank circuit C. Storage circuit B. Store circuit D. Power circuit

C.

0.12

+

j0.16

D.

0.16

+

j0.12

371. REE Board Exam October 1994 A capacitor branch having a ratio of XC to R of 5 is paralleled with impedance consisting of a 4 Ω resistance and a 3 Ω inductive reactance. The power factor of the resulting circuit is 0.8 leading. Find the size of the capacitor in μF if the frequency is 60 Hz. A. 879.9 μF C. 978.9 μF B. 1078.9 μF D. 778.9 μF

377. An impedance of 3 – j3 Ω is connected in parallel with 5 + j2 Ω. The voltmeter connected across 3 Ω resistance measures 45 V. Calculate the total current of the circuit. A. 22.4 A C. 13.4 A B. 41.3 A D. 7.91 A 378. Two impedances ZA = 4 + j6 Ω and ZB are connected in parallel. The apparent power for the impedance B is 1490 VA. Determine the total apparent power. A. 4250 VA C. 2652 VA B. 3290 VA D. 8031 VA 379. A feeder supplies two loads, one at 50 amperes at 50% power factor, the other 150 amperes at unity power factor. The total current supplied by the feeder is approximately ____. A. 180 A C. 175 A B. 200 A D. 150 A 380. A fluorescent lamp and its inductive ballast draw a 1.0 A current at 50% lagging power factor from a

120-V, 60-Hz source. What is the over-all power factor when a 26.5 μF capacitor is connected across the fixture? A. 0.832 lagging C. 0.5 leading B. 0.832 leading D. 0.5 lagging 381. Ten impedances connected in parallel draw the following individual current: 5∠0°, 5∠5°, 5∠10°, 5∠15°, 5∠20°, 5∠25°, 5∠30°, 5∠35°, 5∠40°, 5∠45°. What is the effective value of the total current? A. 48.444 A C. 25.345 A B. 34.255 A D. 84.389 A 382. Ten impedances connected in parallel draw the following individual current: 5∠0°, 5∠5°, 5∠10°, 5∠15°, 5∠20°, 5∠25°, 5∠30°, 5∠35°, 5∠40°, 5∠45°.What is the equivalent impedance that could replace the impedances if the source voltage is 100 sin 150t V? A. 1.325∠ − 30° Ω C. 32.51∠50° Ω B. 6.026∠ − 2.5° Ω D. 𝟏. 𝟒𝟔∠ − 𝟐𝟐. 𝟓° Ω 383. Ten impedances connected in parallel draw the following individual current: 5∠0°, 5∠5°, 5∠10°, 5∠15°, 5∠20°, 5∠25°, 5∠30°, 5∠35°, 5∠40°, 5∠45°. What is the equivalent power factor of the circuit? A. 0.924 C. 0.707 B. 0.866 D. 0.876 384. Ten impedances connected in parallel draw the following individual current: 5∠0°, 5∠5°, 5∠10°, 5∠15°, 5∠20°, 5∠25°, 5∠30°, 5∠35°, 5∠40°, 5∠45°.What element should be connected across the circuit so that the current would be in phase with the source? A. 54 mH C. 13 mH B. 25.4 mH D. 31 mH 385. A small single-phase, 240 V induction motor is tested in parallel with 160 Ω resistor. The motor takes 2 amperes and the total current is 3 amperes. What is the power of the whole circuit? A. 800 W C. 220 W B. 360 W D. 580 W 386. A capacitor is placed in parallel with two inductive loads, one of 20 A at 30° lagging and another of 40 A at 60° lagging. What current in amperes should flow in the capacitor so that the circuit will have a unity power factor? A. 35.8 A C. 28.8 A B. 44.6 A D. 50.2 A 387. A coil of 10 Ω resistance and 0.1 H inductance is connected in parallel with a capacitor of unknown capacitance. If the total impedance of the combination is 100 Ω, determine the value of the capacitance. A. 50 μF C. 150 μF B. 100 μF D. 200 μF

388. An impedance equal to 4.4∠60° Ω is connected across a 220 V source. What should be the value of the second impedance in parallel with the first, if the total power delivered to the circuit is to be 16.5 kW and the overall power factor is to be unity? A. 2.21∠30.1° Ω C. 5.63∠30° Ω B. 𝟑. 𝟑𝟑∠ − 𝟒𝟎. 𝟗° Ω D. 6.543∠ − 45° Ω 389. An inductive reactance of 8 ohms is connected in parallel with a capacitive reactance of 18 ohms. This combination is then connected in series with a variable resistance. For what value of resistance will the power factor be 0.5? A. 8.314 Ω C. 13.81 Ω B. 3.318 Ω D. 1.381 Ω 390. Two impedances Z1 = 3 + j4 and Z2 = 5 – j8.66 ohms respectively are connected in parallel. If the combination is connected across a 240 V AC source, how much is the total current? A. 44.4 A C. 40.6 A B. 42.1 A D. 39.9 A 391. A resistance of 20 ohms and an unknown capacitance are connected in parallel across a 110 V, variable frequency AC source. When the frequency is 60 Hz, the current drawn by the circuit is 6 A. At what frequency will the current drawn fall to 5.8 A? A. 42. 33 Hz C. 46.02 Hz B. 50.12 Hz D. 44.18 Hz 392. Two parallel branches have admittances 0.3 + j0.4 and 0.2 – j0.25 S, respectively. If the current in the first branch is 10 A, determine the total current supplied to the parallel combination. A. 10.44 A C. 15.32 A B. 12.10 A D. 11.24 A 393. An inductive reactance of 3 ohms is connected in parallel with a capacitive reactance of 4 ohms. If the combination is connected in series with a 4 ohm resistance, solve for the power factor of the whole combination. A. 0.333 C. 0.567 B. 0.409 D. 0.316 394. An R-L circuit has Z = (6 + j8) ohm. Its susceptance is ____ siemens. A. 0.06 C. 0.1 B. 0.08 D. -0.08 395. The impedances of two parallel branches of a circuit are (10 + j10) and (10 – j10) respectively. The impedance of the parallel combination is A. 20 + j0 C. 5 – j5 B. 10 + j0 D. 0 – j20 396. Domestic appliances are connected in parallel across ac mains because A. it is a simple arrangement B. operation of each appliance becomes independent of each other

C. D.

appliances have same current ratings this arrangement occupies less space

397. When a parallel ac circuit contains a number of branches, then it is convenient to solve the circuit by A. phasor diagram B. phasor algebra C. equivalent impedance method D. none of the above 398. The power taken by the circuit shown in Fig. 13.1 is IT

IR

IL

R= 30 Ω

XL = 30 Ω

240 V

402. The power consumed in the circuit shown in Fig. 13.2 is IT

IL

XL = 40 Ω

240 V

A. B.

480 W 960 W

C. D.

IL

IR XL = 40 Ω

Fig. 13.1

C. D.

XC = 80 Ω

1200 W none of these

403. The active component of line current in Fig. 13.2 is

240 V

470 W 1920 W

IC R= 60 Ω

Fig. 13.2

IT

A. B.

IR

IC XC = 80 Ω

R= 60 Ω

1200 W none of these Fig. 13.2

399. The active component of line current in Fig. 13.1 is IT

IR

IL

R= 30 Ω

XL = 30 Ω

240 V

A. B.

6A 3A

C. D.

404. The line current drawn by the circuit shown in Fig. 13.2 is IT

A. B.

8A 4A

C. D.

IR

IL

R= 30 Ω

XL = 30 Ω

240 V

A. B.

13 A 6A

C. D.

IL

IR XL = 40 Ω

Fig. 13.1

C. D.

XC = 80 Ω

5A none of these

405. The power factor of the circuit shown in Fig. 13.2 is

240 V

0.707 lagging 0.5 lagging

IC R= 60 Ω

Fig. 13.2

IT

A. B.

IR XL = 40 Ω

5.3 A none of these

400. The power factor of the circuit shown in Fig. 13.1 is IT

IL

240 V

Fig. 13.1

13 A 4A

IC R= 60 Ω

XC = 80 Ω

0.866 lagging none of these Fig. 13.2

401. The total line current drawn by the circuit shown in Fig. 13.1 is IT 240 V

0.8 0.5

C. D.

0.707 none of these

406. The impedance of the circuit shown in Fig. 13.2 is

IR

IL

A. B.

R= 30 Ω

XL = 30 Ω

IT

IL

240 V

IR XL = 40 Ω

IC R= 60 Ω

XC = 80 Ω

Fig. 13.1

A. B.

8/√2 A 16 A

C. D.

𝟖√𝟐 A none of these

Fig. 13.2

A.

180 ohms

C.

48 ohms

B.

24 ohms

D.

none of these IT

407. The circuit shown in Fig. 13.2 is 120 V IT

IR

IL

R2 = 3 Ω

I1

IC

XC = 4 Ω

XL = 3 Ω

XC = 80 Ω

R= 60 Ω

XL = 40 Ω

240 V

I2 R1 = 4 Ω

Fig. 13.3 Fig. 13.2

A. B.

resistive capacitive

C. D.

inductive in resonance

A. B.

capacitive inductive

C. D.

412. If the source frequency of Fig. 13.4 is low, then

408. If in Fig. 13.2, XL is made equal to XC, the line current will be

IT R V

IT

IR

IL

I1

I2

IC

C

L XC = 80 Ω

R= 60 Ω

XL = 40 Ω

240 V

resistive in resonance

Fig. 13.4

Fig. 13.2

A. B.

10 A 6A

C. D.

4A none of these

409. The power consumed in the circuit shown in Fig. 13.3 is IT

coil takes a high lagging current coil takes a low lagging current capacitor takes a leading current circuit offers high impedance

413. If the source frequency of Fig. 13.4 is high, then IT R

I2 R1 = 4 Ω

120 V

A. B. C. D.

V

I1

R2 = 3 Ω

I2

I1 XL = 3 Ω

C

L

XC = 4 Ω Fig. 13.4

Fig. 13.3

A. B.

8400 W 3600 W

C. D.

4000 W none of these

410. If the circuit shown in Fig. 13.3 is connected to 120 V dc, the current drawn by the circuit is

A. B. C. D.

coil takes a high lagging current capacitor takes a high leading current capacitor takes a low leading current circuit offers high impedance

414. The circuit shown in Fig. 13.5 is IT

IT

I2 R1 = 4 Ω

120 V

100 V

R2 = 3 Ω

24 A 70 A

Fig. 13.5

A. B.

411. The circuit shown in Fig. 13.3 is

C. D.

XC = 4Ω

XC = 4 Ω

Fig. 13.3

A. B.

I2 XL = 4Ω

I1 XL = 3 Ω

R= 3Ω

I1

48 A 30 A

in resonance resistive

C. D.

inductive capacitive

415. The circuit shown in Fig. 13.5 will consume a power of

B. IT 100 V

R= 3Ω I2

100 V

C. D.

500 W none of these

416. If the admittance of a parallel ac circuit is increased, the circuit current A. remains constant C. is increased B. is decreased D. none of these 417. The admittance of the circuit shown in Fig. 13.6 is R=6Ω XL = 8 Ω

Fig. 13.6

A. B.

10 S 14 S

C. D.

0.1 S none of these

418. The conductance of the circuit shown in Fig. 13.6 is R=6Ω XL = 8 Ω

Fig. 13.6

A. B.

14 S 0.6 S

C. D.

0.06 S none of these

419. The inductive susceptance of the circuit shown in Fig. 13.6 is R=6Ω XL = 8 Ω

Fig. 13.6

A. B.

8S 0.8 S

none of these

XC = 4Ω

Fig. 13.5

1200 W 2400 W

D.

421. The power loss in the circuit shown in Fig. 13.7 is

I1 XL = 4Ω

A. B.

inductive

C. D.

0.08 S none of these

G= 0.01 S

-B

Fig. 13.7

A. B.

100 W 10,000 W

C. D.

10 W none of these

422. The conductance and susceptance components of admittance are A. series elements B. parallel elements C. series-parallel elements D. none of the above 423. The impedance of a circuit is 10 ohms. If the inductive susceptance is 1 siemen, then inductive reactance of the circuit is A. 10 ohms C. 100 ohms B. 1 ohm D. none of these 424. The conductance and inductive susceptance of a circuit have the same magnitude. The power factor of the circuit is A. 1 C. 0.707 B. 0.5 D. 0.866 425. The admittance of a circuit is (0.1 + j0.8) S. The circuit is A. resistive C. inductive B. capacitive D. none of these 426. In a parallel ac circuit, power loss is due to A. conductance alone B. susceptance alone C. both conductance and susceptance D. none of the above 427. The admittance of a parallel circuit is 0.12∠ − 30° S. The circuit is A. inductive C. resistive B. capacitive D. none of these

420. The circuit shown in Fig. 13.7 is

428. A circuit have an impedance of (1 – j2) ohms. The susceptance of the circuit is A. 0.1 S C. 0.4 S B. 0.2 S D. none of these

G= 0.01 S

429. A circuit has admittance of 0.1 S and conductance of 0.08 S. The power factor of the circuit is A. 0.1 C. 0.08 B. 0.8 D. none of these

100 V

-B

Fig. 13.7

A.

resistive

C.

capacitive

430. When an sinusoidal voltage is applied across R-L parallel circuit so that R = XL the phase angle will be A. 45° lagging C. 90° lagging

45° leading

D.

90° leading

431. In a parallel R-L circuit if IR is the current in resistor and IL is the current in the inductor, then A. IR lags IL by 90° C. IL leads IR by 270° B. IR leads IL by 270° D. IL lags IR by 90° 432. The current read by the ammeter A in the ac circuit shown is the given figure is

1A

9A 5A

3A

-j120 j60

1+j 1 + j0

C. D.

5A

2-j 0 + j0

C. D.

3A 1A

1.5 + j-.5 5 – j18

YL

YC

C. D.

0.5 F

V  20

E ω = 2 rad/s

A. B.

1Ω

1F

R2

2 Ω, 1 Ω 1 Ω, 2 Ω

C. D.

3 Ω, 2 Ω 2 Ω, 3 Ω

438. The total impedance Z(jω) of the circuit shown is 17/6 Ω

3Ω

0.5 + j1.8 5 – j12

434. For the circuit shown in the figure, how much the voltage across the inductor leads the voltage across the capacitor? L

1F

Z(s)

E  100 V

YR

I

1Ω

R1

433. In the given figure, the admittance values of the elements in siemens are YR = 0.5 + j0, YL = 0 – j1.5 and YC = 0 + j0.3 respectively. The value of I as a phasor when the voltage E across the elements is 10√0° V is

A. B.

A. B.

60

437. For the network shown in the given figure Z(0) = 3 Ω and Z(∞) = 2 Ω. The values of R1 and R2 will respectively be

A

A. B.

I

v(t) = 120 sin ωt

B.

3Ω

j4 Ω

-j4 Ω

A. B.

6 + j0 Ω 7 + j0 Ω

C. D.

0 + j8 Ω 6 + j8 Ω

439. A resistance of 40 ohms and an inductive reactor of 30 ohms are joined in parallel to a 120 volts supply as shown in the figure. The power factor of the circuit is I1

R = 40 Ω

I2

X = 30 Ω

I

A. B.

45° 90°

C. D.

135° 180°

435. In the circuit shown in the figure, v = cos 2t, Z2 = 1 + j. C1 is chosen so that i = cos 2t. The value of C1 is I VS

A. B.

2F 1F

C1

C. D.

Z2

0.5 F 0.25 F

436. For the given ac circuit, what is the value of I?

120 volts

A. B.

0.6 0.7

440. In a parallel RC circuit, A. IC lags IR by 90° 90° B. IR and IC are in phase 90°

C. D.

0.8 unity

C.

IC leads IR by

D.

IR leads IC by

441. In a parallel RC circuit, A. VC and IR are in phase B. VC and IC are in phase C. IC and IR are in phase D. VC and IR are 90° out of phase

442. When the frequency of the applied voltage increases in a parallel RC circuit A. the phase angle, θT, increases B. ZEQ increases C. ZEQ decreases D. both A and C 443. In a parallel RL circuit, A. iL lags iR by 90° B. iL leads iR by 90° C. iL and iR are in phase D. iR lags iL by 90°

451. EE Board Exam April 1993 Capacitor of 30-microfarad capacitance is in series with a coil across an 8,000 cycle supply. What inductance is required for resonance? A. 13.34 μH C. 13.19 μH B. 10.45 μH D. 12.55 μH 452. REE Board Exam October 1998 One leg of a radio tuned circuit has a capacitance of 1 x 10-9 F. It is tuned at 200 kHz. What is the inductance of the other leg in Henry? A. 6.33 x 10-4 C. 8.25 x 10-5 -3 B. 20 x 10 D. 120 x 10-3

444. In a parallel RL circuit, A. VT and IL are in phase B. IL and IR are in phase C. VT and IR are in phase D. VT and IR are 90° out of phase 445. When the frequency of the applied voltage decreases in a parallel RL circuit A. the phase angle, θI, becomes less negative B. ZEQ increases C. ZEQ decreases D. both A and B 446. When the frequency of the applied voltage increases in a parallel RL circuit A. θZ increases C. ZT increases B. ZT decreases D. both A and C 447. In an ac circuit with only parallel inductors A. IT lags VT by 90° C. VT and IT are in phase B. VT lags IT by 90° D. none of the above 448. In a parallel ac circuit with XL and XC A. IL and IC are 90° out of phase B. IL and IC are in phase C. IL and IC are 180° out of phase D. XL and XC are 90° out of phase D. RESONANCE 449. REE Board Exam October 2000 A series circuit consists of a 20-ohm resistance, a 150 mH inductance and an unknown capacitance. The circuit is supplied with a voltage v = 100 sin 377t. Find the value of capacitance at resonance. A.

42 μF

C.

34.65 μF

B.

47 μF

D.

72.57 μF

450. REE Board Exam April 2001 A 5 mH pure inductance is connected in parallel with one microfarad capacitor. What frequency will the circuit be antiresonance? A.

250 Hz

C.

60 Hz

B.

2250 Hz

D.

100 Hz

453. EE Board Exam April 1988 A loud speaker whose inductance is 1.15 Henry is coupled to a power tube through a condenser of 2 μF capacity. To what frequency will the combination be resonant? A. 110 Hz C. 105 Hz B. 108 Hz D. 100 Hz 454. REE Board Exam April 1995 What capacitance must be placed in series with an inductance of 0.05 Henry so that at 100 Hz, the impedance becomes equal to the ohmic resistance? A. 50.7 μF C. 70.7 μF B. 35.5 μF D. 87.0 μF 455. EE Board Exam April 1989 A coil has a resistance of 50 ohms and a reactance of 100 ohms, is shunted by a capacitor, which has practically no losses in order that the voltage across the coil be in phase with the total current supplied to the parallel combination. What is the impedance of the parallel combination under the given condition? A. 250 ohms C. 230 ohms B. 200 ohms D. 220 ohms 456. EE Board Exam April 1983 A non-inductive resistor R is connected in parallel with an inductive reactance of 10 ohms. The combination is then connected in series with a capacitive reactance of 5 ohms. Solve for R at which the power factor of the given circuit would be unity. A. 10 Ω C. 13 Ω B. 12 Ω D. 11 Ω 457. EE Board Exam October 1982 Two impedances Z1 = 15 + j20 and Z2 = 5 – jXC are connected in parallel. Solve for the values of XC so that the total current drawn by the combination will be in phase with any supply voltage V. A. 28.54  C. 33.12  B. 30.43  D. 29.55  458. EE Board Exam April 1985 A resistance of 5 ohms is connected in series with a capacitor of 442.1 μF. The combination is then connected in parallel with an inductance of 21.22 mH. Solve for the frequency of the impressed voltage

with which the inductive reactance is equal to the capacitive reactance in magnitude. A. 50 Hz C. 52 Hz B. 51 Hz D. none of these 459. EE Board Exam April 1989 A coil has a resistance of 50 ohms and a reactance of 100 ohms, is shunted by a capacitor, which has practically no losses. What must be the reactance of the capacitor in order that the voltage across the coil is in phase with the total current supplied to the parallel combination? A. 120 ohms C. 125 ohms B. 127 ohms D. 132 ohms 460. EE Board Exam April 1982 Three impedances Za, Zb and Zc are connected in parallel. If at 60 Hz, Za = j8, Zb = -j2 and Zc = 5 ohms, Solve for the frequency at resonance. A. 30 Hz C. 36 Hz B. 34 Hz D. 28 Hz 461. EE Board Exam April 1981 A resistor R is connected in parallel with a 20-ohm inductive reactive. The combination is then connected in series with a 5-ohm capacitive reactance. Solve the value of R at which the power factor of the resultant impedance is unity. A. 10.05 ohms C. 11.55 ohms B. 9.15 ohms D. 10.73 ohms 462. EE Board Exam October 1998 A coil has a resistance of 50 ohms and a reactance of 70 ohms. A capacitor is connected in parallel to produce resonance. The source voltage is 120 V. What is the power drawn by the circuit? A. 162 W C. 132 W B. 97 W D. 52 W 463. EE Board Exam April 1995 A coil is supplied with 200 volts and takes a current (rms) of 2 amperes at 0.707 lagging. The quality factor (Q) of the coil is A. 25 C. 10 B. 1 D. 100 464. EE Board Exam October 1998 In a series resonant RLC circuit, all of the following statements are correct EXCEPT one. Which one is this? A. The resonant frequency is dependent on the resistance of the circuit. B. The phase angle between the voltage and the current vectors is zero. C. The impedance is a minimum. D. The current is a maximum. 465. EE Board Exam April 1994, October 1993 The current in RLC series circuit at resonance is A. maximum C. minimum B. zero D. infinity 466. ECE Board Exam April 2001

Ignoring the capacitive effects, what is the impedance of a 100 mH coil (with an internal resistance of 45 ohms) in parallel with 4,700 ohms resistor at a frequency of 500 Hz? A. 317 ohms C. 5014 ohms B. 237 0hms D. 314 ohms 467. ECE Board Exam November 1996 ____ frequency is reached when the capacitive and inductive reactance in a tuned circuit are equal. A. zero C. infinite B. pulsating D. resonant 468. ECE Board Exam November 1998 Find the Q of a circuit when the resonant frequency is 4.468 MHz, the inductance is 47 microhenry and the resistance is 180 ohms parallel. A. 0.136 C. 0.00735 B. 13.30 D. 7.35 469. ECE Board Exam November 2000 In an “IDEAL” resonant circuit, what is the relationship between the current and the impedance? A. current high, impedance low B. current low, impedance low C. current low, impedance high D. current high, impedance high 470. ECE Board Exam November 1997 What condition does resonance occurs in an electrical circuit? A. When the power factor is at minimum B. When the square root of the sum of the capacitive and inductive reactances is to the resonant frequency C. When the inductive and capacitive reactances are equal D. none of the above 471. ECE Board Exam November 2001 What is the relationship between frequency and the value of XC? A. frequency has no effect B. XC varies directly with frequency C. XC varies inversely with frequency D. XC varies indirectly with frequency 472. ECE Board Exam April 2001 When is the line current minimum in a parallel LC circuit? A. at the broadcast frequency B. at the circuit frequency C. at the resonant frequency D. at the highest frequency 473. ECE Board Exam November 1999 Find the half-power bandwidth of a parallel resonant circuit which has a resonant frequency of 7.1 MHz and Q of 150. A. 16.5 kHz C. 21.1 kHz B. 211 kHz D. 47.3 kHz

474. ECE Board Exam November 1997 It is the term for the phenomena which occurs in an electrical circuit when the inductive reactance balances with the capacitive reactance. A. reactive equilibrium C. reactive quiescence B. resonance D. high Q 475. ECE Board Exam April 1998 What is the resonant frequency of a circuit when L of 25 microhenrys and C of 10 picofarads are in parallel? A. 68.7 kHz C. 68.7 MHz B. 10.1 kHz D. 10.1 MHz 476. ECE March 1996 What is the effect in terms of bandwidth when the Q of a single-tuned stage is doubled? A. halved C. doubled B. the same D. four times 477. ECE Board Exam November 1999 If you need an LC circuit to be resonant at 2,500 Hz and use a 150 mH coil, what should the capacitance value be? A. 0.015 μF C. 27 μF B. 0.15 μF D. 0.027 μF 478. ECE Board Exam April 1999 What is the resonant frequency of a circuit when L is 40 microhenrys and C is 6 picofarads are in series? A. 6.63 MHz C. 6.63 kHz B. 10.3 MHZ D. 10.3 kHz 479. ECE Board Exam April 1998 What is the resonant frequency of a circuit when L of 3 microhenrys and C of 40 picofarads are in series? A. 14.5 MHz C. 1.33 kHz B. 1.33 MHz D. 14.5 kHz 480. ECE Board Exam November 2001 ____ refers to reactive power. A. power consumed in circuit Q B. power consumed in wire resistance in an inductor C. wattles, non-productive power D. power lost because of capacitor leakage 481. ECE Board Exam November 1998 How do you call the nature of a circuit during series resonance? A. unstable C. resistive B. capacitive D. inductive 482. ECE Board Exam April 1999 What is the resonant frequency of a circuit when L is 200 microhenrys and C is 10 picofarads are in series? A. 7.96 MHz C. 3.56 MHz B. 6 MHz D. 7.96 kHz 483. ECE Board Exam April 2000

In a series resonant LC circuit, what is the impedance at resonant frequency? A. Infinity B. Determined solely by the dc resistance C. The maximum impedance value D. Zero 484. ECE Board Exam April 1999 What is the characteristic of the current parallel R-L-C circuit at resonance? A. The current circulating in the parallel is dc B. The current circulating in the parallel is zero C. The current circulating in the parallel is at a maximum D. The current circulating in the parallel is at a minimum

flow in a elements elements elements elements

485. ECE Board Exam March 1996 What is the responsible for the phenomenon when voltages across reactances in series can often be larger than the voltage applied to them? A. Capacitance C. Conductance B. Resistance D. Resonance 486. ECE Board Exam March 1996 Term used for resonance in an electrical circuit. A. The frequency at which power factor is at a minimum B. The frequency at which capacitive reactance equals inductive reactances C. The highest frequency that will pass current D. The lowest frequency that will pass current 487. ECE Board Exam November 1998 Ignoring any effects of dc resistance, what is the total reactance of a 250 mH coil in series with a 4.7 F capacitor at a signal frequency of 1000 Hz? A. 1604  C. 1536  B. 35  D. 1570  488. ECE Board Exam November 1996 The _____ the Q of a circuit, the narrower is its bandwidth. A. Lower C. Higher B. Broader D. Selective 489. ECE Board Exam March 1996 Find the half-power bandwidth of a resonant circuit which has a resonant frequency of 1.8 MHz and a Q of 95. A. 58.7 kHz C. 189 Hz B. 18.9 kHz D. 1.89 kHz 490. ECE Board Exam November 1998 What is the resonant frequency of a circuit when L is 5 microhenrys and C is 9 picofarads are in series? A. 23.7 kHz C. 23.7 MHz B. 3.54 kHz D. 3.54 MHz 491. ECE Board Exam April 1998

Find the half-power bandwidth of a parallel resonant circuit which has a resonant frequency of 3.6 MHz and a Q of 218. A. 58.7 kHz C. 16.5 kHz B. 606 kHz D. 47.3 kHz 492. ECE Board Exam November 1998 What is the resonant frequency of a circuit when L is 3 microhenrys and C is 40 picofarads are in parallel? A. 14.5 kHz C. 14.5 MHz B. 13.1 kHz D. 13.1 MHz 493. ECE Board Exam November 1998 What is the resonant frequency of a circuit when L is 15 microhenry and C is 5 picofarads are in series? A. 2.12 kHz C. 18.4 kHz B. 18.4 MHz D. 2.12 MHz 494. ECE Board Exam November 1998 What is the resonant frequency of a circuit when L is 2 microhenry and C is 15 picofarads are in series? A. 29.1 MHz C. 29.1 kHz B. 5.31 MHz D. 5.31 kHz 495. ECE Board Exam April 1998 Characteristic of the current flow in a series R-L-C circuit at resonance A. it is zero B. it is dc C. it is at a maximum D. it is at a minimum 496. ECE Board Exam April 2001 What is the term for the number of times per second that a tank circuit energy is stored in the inductor of capacitor? A. Non-resonant frequency B. Broadcast frequency C. Circuit frequency D. Resonant frequency 497. ECE Board Exam November 1995 An LC circuit resonates at 2000 kHz, and has a Q of 100. Find the lower and upper cut-off frequencies. A. 1950 kHz, 2050 kHz C. 1980 kHz, 2020 kHz B. 1990 kHz, 2010 kHz D. 1900 kHz, 2100 kHz 498. ECE Board Exam November 1998 What is the resonant frequency of a circuit when L is 50 microhenrys and C is 10 picofarads are in parallel? A. 3.18 kHz C. 7.12 MHz B. 3.18 MHz D. 7.12 kHz 499. ECE Board Exam November 1999 What is the cause of a minimum Q on a single-tuned LC circuit? A. Decreased shunt resistor B. Decreased capacitance C. Increased shunt resistor D. Decreased series resistor

500. ECE Board Exam November 1998 ____ is another term for quality factor or Q of the resonant circuit. A. Noise factor C. White noise B. Noise figure D. Figure of merit 501. ECE Board Exam November 2000 What is the biggest advantage of using crystals in resonant circuits? A. less fragile B. cost C. size D. greater accuracy and stability 502. ECE Board Exam April 2001 What is the impedance of a crystal at its resonant frequency when it is used in the parallel mode? A. 70 percent C. minimum B. 50 percent D. maximum 503. ECE Board Exam April 1998 _____ is a parallel LC circuit. A. Hartley circuit B. Static circuit C. Tank circuit D. Parallel resisting circuit 504. There will ____ be a frequency, called the ____ frequency at which ____. A. sometimes, natural; XL = XC B. always, natural; R = 0 C. always, resonant; XL = XC D. sometimes, resonant; R = 0 505. The formula for the resonant frequency is f = ____. A. √LC C. 1/√LC 𝟏 B. 2π√LC D. 𝟐𝛑√𝐋𝐂

506. For a series RLC circuit, a circuit at resonance the current amplitude is ____ for a fixed voltage amplitude and the power factor is ____. A. minimum, zero C. maximum, zero B. minimum, unity D. maximum, unity 507. In an RLC circuit, the impedance at resonance is A. maximum C. infinity B. minimum D. zero 508. The current in RLC series circuit, i.e., at resonance is A. maximum C. infinity B. minimum D. zero 509. In RLC circuits, the current at resonance is A. the maximum in series circuit and minimum in parallel circuit B. maximum in parallel circuit and minimum in series circuit C. maximum in both the circuits D. minimum in both the circuits

510. A series resonant circuit is capacitive at f = 100 Hz. The circuit will be inductive somewhere at A. f = 100 Hz B. f > 100 Hz C. f = 100 Hz by increasing the value of the resistance D. none of these 511. At a frequency less than the resonant frequency A. series circuit is capacitive and parallel circuit is inductive B. series circuit is inductive and parallel circuit is capacitive C. both circuits are inductive D. both circuits are capacitive 512. In series as well as parallel resonant circuits, increasing the value of resistance would lead to A. increase in the bandwidth of both the circuits B. decrease in the bandwidth of both the circuits C. increase in bandwidth in series circuit and decrease in parallel circuit D. decrease in bandwidth in series circuit and increase in parallel circuit

B.

f=

1 2π√LC−R2

D.

1

f= 2π√

LC−C2 R2 2

518. The frequency at which maximum voltage occurs across the capacitance in RLC series circuits is 1 1 A. f = C. f = 2 2π√LC

B.

𝐟=

𝟏 𝟏 𝐑𝟐 𝟐𝛑√ − 𝟐 𝐋𝐂 𝐋

2π√

D.

R 2L2

1

f= 2π√

1 R2 − L𝐶2 2L

519. If f1 and f2 are half power frequencies and f0 be resonance frequency, the selectivity of RLC series circuit is given by f −f 𝐟 −𝐟 A. 2 0 C. 𝟐 𝟏 B.

f1 −f0 f2 −f1 f0

D.

𝐟𝟏 −𝐟𝟎 f2 −f1 2f0

520. To a series RLC circuit, a voltage of 10 V is applied. If Q of the coil at resonant frequency is 20, the voltage across the inductor at resonant frequency will be A. 200 V C. 75 V B. 100 V D. 50 V

513. The value of current at resonance in a series RLC circuit is affected by the value of A. R C. C B. L D. all of these

521. The currents flowing in L and C at parallel resonance are A. zero C. infinite B. equal D. different

514. In resonant circuits, the power factor at resonance is A. zero C. 1 B. 0.5 D. 0.707

522. The exact natural frequency of free oscillation in an oscillatory circuit with capacitance of 0.055 μF, inductance 2 μH and resistance 1 ohm will be A. 478 kHz C. 272 kHz B. 337 kHz D. 192 kHz

515. Which of the following statements is true for a series RLC circuit tuned at resonant frequency? A. the voltage across C > applied voltage B. the voltage across L > applied voltage C. the voltage across L and C > applied voltage D. the voltage across L and C = applied voltage 516. At anti-resonance for the given circuit, the frequency is given by

A.

𝐟=

1 2π√LC

B.

√

1

√

√

𝐋−𝐂𝐑𝟐𝟏 𝐋−𝐂𝐑𝟐𝟐

R2

L

C

C.

f=

526. A resonance curve for a series circuit is a plot of frequency versus ____. A. voltage C. current B. impedance D. reactance

C−LR22 1 √LC

L−CR21 L−CR22

√

D.

f=

L−CR21 C−CR22

517. The frequency at which maximum voltage occurs the inductance in RLC series circuits is 1 𝟏 A. f = C. 𝐟 = 𝟐 𝟐 2π√LC

524. In a series R-L-C circuit, resonance occurs when A. R = XL - XC C. XL = 10 XC or more B. XL = XC D. net X > R 525. The p.f. of a series R-L-C circuit at its half-power point is A. unity C. leading B. lagging D. either B and C

C−LR21

f=

2π√LC

𝟏 𝟐𝛑√𝐋𝐂

R1

523. A coil with large distributed capacitance has a A. low resistance B. low Q C. low resonant frequency D. high resonant frequency

𝑪 𝑹 𝟐

𝟐𝛑√𝐋𝐂−

527. At half-power points of a resonance curve, the current is ____ times the maximum current. A. 2 C. √𝟐 B. 1/√2 D. 1/2

528. Higher the Q of a series circuit, A. greater its bandwidth B. sharper its resonance C. broader its resonance curve D. narrower its pass band 529. As the Q-factor of a circuit ____, its selectivity becomes ____. A. increases, better C. decreases, better B. increases, worse D. decreases, narrower 530. An R-L-C circuit has a resonance frequency of 160 kHz and a Q-factor of 100. Its bandwidth is A. 1.6 kHz C. 16 MHz B. 0.625 kHz D. none of the above 531. In a parallel resonant circuit there is practically no difference between the condition for unity power factor and the condition for maximum impedance so long as Q is A. very small of the order of 5 B. small of the order of 20 C. large of the order of 1000 D. none of these 532. A parallel AC circuit in resonance will A. act like a resistor of low value B. have a high impedance C. have current in each section equal to the line current D. have a high voltage developed across each inductive and capacitive section 533. A parallel resonant circuit can be used A. to amplify certain frequencies B. to reject a small band of frequencies C. as a high impedance D. both B and C 534. The Q-factor of a 2-branched parallel circuit is given by the ratio A. Ic/IL C. I/IL B. I/Ic D. L/C

537. Consider the following statements with respect to a series R-L-C circuit under resonance condition: 1. All the applied voltage appears across R. 2. There is no voltage across either L or C. 3. The voltage across L and C is equal and equal to their maximum values. Of these statement A. 1 alone is correct C. 1 and 3 are correct B. 2 alone is correct D. 1 and 2 are correct 538. A series R-L-C circuit will have unity power factor if operated at a frequency of A. 1/LC C. 1/ω2LC B. 1/ω√LC D. 𝟏/𝟐𝛑√𝐋𝐂 539. A series resonant circuit implies A. zero pf and maximum current B. unity pf and maximum current C. unity pf and minimum current D. zero pf and minimum current 540. Consider the following statements: In a network of resonance: 1. the admittance is maximum 2. the power factor is unity irrespective of the network 3. the Q of a series RLC resonant circuit is independent of R Of these statements A. 1 and 3 are correct C. 2 and 3 are correct B. 1 and 2 are correct D. 1 alone is correct 541. A circuit with a resistor, inductor and capacitor in series is resonant at f0 Hz. If all the component values are now doubled the new resonant frequency is A. 2f0 C. f0/4 B. still f0 D. f0/2 542. If the resonant frequency of the circuit shown in Fig. 1 is 1 kHz, the resonant frequency of the circuit shown in Fig. 2 will be 100 Ω

535. Like a resonant R-L-C, a parallel resonant circuit also A. has a power factor of unity B. offers minimum impedance C. draws maximum current D. magnifies current 536. At resonant frequency an R-L-C circuit draws maximum current due to the reason that A. the difference between capacitive reactance and inductive reactance B. the impedance is more than resistance C. the voltage across the capacitor equals the applied voltage D. the power factor is less than unity

L

C

Fig. 1 R

L

C L

C

Fig. 2

A. B.

4 kHz 2 kHz

C. D.

0.5 kHz 0.25 kHz

543. In the circuit shown in the given figure, the magnitude of VL and VC are twice that of VR. The inductance of the coil is

VR

VL

VC

5Ω

L

C

C. D.

50 V

A. B.

2.14 mH 5.30 mH

C. D.

31.8 mH 1.32 mH

544. In a series RLC circuit at resonance, the magnitude of voltage developed across the capacitor A. is always zero B. can never be greater than the input voltage C. can be greater than the input voltage however it is 90° out of phase with the input voltage D. can be greater than the input voltage and is in phase with the input voltage 545. A coil having a resistance of 5 Ω and inductance of 0.1 H is connected in series with a capacitor of capacitance 50 μF. A constant alternating voltage of 200 V is applied to the circuit. The voltage across the coil at resonance is A. 200 volts C. 1,800 volts B. 1,788 volts D. 2,000 volts 546. A series R-L-C circuit, excited by a 100 V variable frequency supply, has a resistance of 10 Ω and an inductive reactance of 50 Ω at 100 Hz. If the resonance frequency is 500 Hz, what is the voltage across the capacitor at resonance? A. 100 V C. 2,500 V B. 500 V D. 5,000 V 547. The resonant frequency of the given series circuit is M=1H 2H

A. B.

1 2𝜋√3 𝟏 𝟒𝝅√𝟑

2F

552. When Q-factor of a circuit is high, then A. power factor of the circuit is high B. impedance of the circuit is high C. bandwidth is large D. none of these 553. Consider the following statements regarding the frequency response curve of a series RLC circuit: 1. At half-power frequencies, the current in the circuit is one half of the current at resonant frequencies 2. At half-power frequencies, the power factor angle of the circuit is 45° 3. At resonant frequency, the power factor angle of the circuit is 90° 4. Maximum power occurs at resonant frequency Of these statements A. 1, 2 and 4 are correct C. 2 and 4 are correct B. 1, 2 and 3 are correct D. 1 and 4 are correct 554. An RLC series circuit has f1 and f2 as the half power frequencies and f0 as the resonant frequency. The Qfactor of the circuit is given by: 𝑓 +𝑓 𝒇𝟎 A. 1 2 C. B.

Hz

D.

1 4𝜋√2 1 𝜋√2

D.

𝑓2 −𝑓0

𝒇𝟏 −𝒇𝟐 𝑓1 −𝑓2 𝑓0

2

2H

C.

2𝑓0 𝑓1 −𝑓0

555. Resonant frequency fr of a series RLC circuit is related to half power frequencies f1 and f2 as 𝑓 +𝑓 A. 𝑓𝑟 = 1 2 C. 𝑓𝑟 = 𝑓2 − 𝑓1 B.

Hz

voltage increases voltage decreases

Hz

Hz

548. In a series R-L-C circuit, the maximum voltage across the capacitor occurs at a frequency A. double the resonant frequency B. equal to the resonant frequency C. √2 times the resonant frequency D. below the resonant frequency 549. For a series RLC circuit, the power factor at the lower power frequency is A. 0.5 lagging C. unity B. 0.5 leading D. 0.707 leading 550. Q-factor of a series RLC circuit possessing resonant frequency of 10 Hz and bandwidth of 5 Hz is A. 0.5 C. 2.5 B. 2 D. 50 551. The quality factor of RLC circuit will increase if A. R decreases B. R increases

𝒇𝒓 = √𝒇𝟏 𝒇𝟐

D.

𝑓𝑟 = √𝑓1 + √𝑓2

556. A series RLC circuit has R = 50 Ω, L = 100 μH and C = 1 μF. The lower half power frequency of the circuit is A. 30.55 kHz C. 51.92 kHz B. 3.055 kHz D. 1.92 kHz 557. For a series RLC resonant circuit, what is the total reactance at the lower half power frequency? A. √2𝑅∠45° C. R B. √2𝑅∠ − 45° D. -R 558. A series RLC circuit when excited by a 10 V sinusoidal voltage source of variable frequency, exhibits resonance at 100 Hz and has a 3 dB bandwidth of 5 Hz. The voltage across the inductor L at resonance is A. 10 V C. 10/√2 B. 10√2 V D. 200 V 559. An RLC resonant circuit has a resonant frequency of 1.5 MHz and a bandwidth of 10 kHz. If C = 150 pF, then the effective resistance of the circuit will be A. 29.5 Ω C. 9.4 Ω

B.

14.75 Ω

D.

4.7 Ω

2.

The impedance of the whole circuit is independent of frequency, if RL = RC and ω = 1/√LC . 3. The circuit is in resonance for all the frequencies if RL = RC. 4. The two branch currents will be in phase at ω = 1/√LC. Which of the above statements are correct? A. 1 and 2 C. 1 and 3 B. 2 and 3 D. 3 and 4

560. The following circuit resonates at 1F

4H 10 Ω

1F +

A. B.

all frequencies 0.5 rad/s

-

C. D.

5 rad/s 1 rad/s

566. The value of Z in given figure which is most appropriate to cause parallel resonance at 500 Hz is

561. A choke coil of inductance L and series resistance R is shunted by a capacitor. The dynamic impedance of the resonant circuit would be A. R/(LC) C. L/(RC) B. C/(RL) D. 1/(RLC) 562. For the following circuit, the current source is sinusoidal with frequency equal to the resonant frequency of the circuit. What is the value of current through resistor?

I

A. B.

0.1 H

0 0.11

10 Ω

0.1 F

C. D.

5Ω

A. B.

125 mH 304.2 μF

1 10.1

A. B.

0A 10 A

IR

C. D.

50 μF

0.5 H

R

5A 0.5 A

564. A circuit has two parallel branches. In one branch, R and L are connected in series while in the other R and C are connected in series. If R = √L/C, which of the following is not correct? A. The circuit is in resonance. B. The two branch currents are in quadrature. C. The circuit has an impedance independent of its frequency. D. The two branch currents are in phase. 565. A parallel circuit consists of two branches. One branch has RL and L connected in series and the other branch has RC and C connected in series. Consider the following statements: 1. The two branch currents will be in quadrature if RLRC = L/C.

C. D.

2 μF 0.05 μF

567. The value of the capacitance ‘C’ in the given ac circuit to make it a constant resistance circuit or for the supply current to be independent of its frequency is

563. In the given circuit, at resonance IR amperes is equal to

5A

Z

2H

A. B.

1/16 F 1/12 F

4Ω

4Ω

1H

C

C. D.

1/8 F 1/4 F

568. A coil takes apparent power and reactive power of 100 VA and 80 VAR, respectively. What is the Q factor of the coil? A. 1.33 C. 8 B. 10 D. 6 569. A 50 Ω resistance, a 30 Ω inductive reactance and a 25 Ω capacitive reactance are connected in series across a 100 V, 60 Hz supply. What will be its resonant frequency? A. 65.726 Hz C. 25 Hz B. 53 Hz D. 54.77 Hz 570. A coil having a Q factor of 5 is connected in series with an ideal capacitor across ac source of 60 V. Calculate the voltage across the capacitor at resonance. A. 150 V C. 12 V B. 300 V D. 65 V 571. A coil having an inductance of 50 mH and a resistance 10 Ω is connected in series with a 25 μF capacitor across a 200 V ac supply. Find the value of Q factor?

A. B.

7.4 4.53

C. D.

3.54 4.47

572. The following data are given for a series RL and a series RC which are connected in parallel: XL = 15 Ω, XC = 25 Ω, RC = 15 Ω. For value of RL will the circuit be in resonance? A. 169 ohms C. 16.9 ohms B. 916 ohms D. 91.6 ohms 573. A circuit consisting of a capacitor in series with a resistance of 10 ohms is connected in parallel with a coil having a reactance and resistance of 17.32 ohms and 10 ohms respectively. What is the reactance of the capacitor that will draw minimum current from a 230-V, 60 Hz supply? A. 17.32 Ω C. 6.78 Ω B. 10.32 Ω D. 22.18 Ω 574. Series circuit consists of a 20-ohm resistance, a 150 mH inductance and an unknown capacitance. The circuit is supplied with a voltage v = 100 sin 377t. Find the value of capacitance at resonance. A. 42 μF C. 47 μF B. 72.567 μF D. 34.65 μF 575. A coil having a resistance of 0.5 ohm and an inductance of 5.25 mH is connected in parallel with a capacitor across a 220 volt, 60 Hz source. Calculate the value of the capacitance at resonance. A. 125 microfarad C. 125 millifarad B. 1.25 microfarad D. 1.25 millifarad 576. The current in an RL and C parallel circuit at resonance is A. maximum C. minimum B. zero D. infinity 577. A circuit draws 25 A when connected across a source of frequency f1. Determine the current drawn by the same circuit at resonance if f1 is half the resonant frequency. A. 12.5 A C. 35.35 A B. 17.68 A D. 50 A 578. A series RLC circuit is connected across a 120-V, 60 Hz source and draws a leading current of 5 A. Determine the voltage across the capacitor at resonance if R = 5 Ω and L = 25 mH. A. 47.12 V C. 236.6 V B. 164.5 V D. 422.6 V 579. The best definition of Q-factor of a coil is A. The ratio of its maximum energy stored to its energy dissipated per cycle B. Its power factor C. The reciprocal of its reactive factor D. The ratio of its resistance to its inductive reactance 580. A coil is to be wound with Q-factor of 8. A lamp rated 120 V, 480 W is connected in series with the coil and connected across 230 V, 60 Hz source. What is the

impedance of the coil if the voltage across the lamp is maintained at 120 V? A. 35.2∠82.9° Ω C. 𝟒𝟓. 𝟓∠𝟖𝟐. 𝟗° Ω B. 27.5∠72.4° Ω D. 40.5∠72.4° Ω 581. An inductive coil having a resistance of 25 ohms and inductance of 0.2 H is connected in parallel with a 100 μF capacitor. Find the frequency at which the total current taken is in phase with the supply voltage. A. 35.6 Hz C. 29.5 Hz B. 46.5 Hz D. 52.9 Hz 582. The resonant frequency of an LC circuit is the frequency where A. XL = 0 Ω and XC = 0 Ω B. XL = XC C. XL and rS of the coil are equal D. XL and XC are in phase 583. The impedance of a series LC circuit at resonance is A. maximum C. minimum B. nearly infinite D. both A and B 584. The total line current, IT, of a parallel LC circuit at resonance is A. minimum B. maximum C. equal to IL and IC D. Q times larger than IL or IC 585. The current at resonance in a series LC circuit is A. zero B. minimum C. different in each component D. maximum 586. The impedance of a parallel LC circuit at resonance is A. zero B. maximum C. minimum D. equal to the rS of the coil 587. The phase angle of an LC circuit at resonance is A. 0° C. 180° B. 90° D. -90° 588. Below resonance, a series LC circuit appears A. inductive C. capacitive B. resistive D. none of above

the

589. Above resonance, a parallel LC circuit appears A. inductive C. capacitive B. resistive D. none of the above 590. When either L or C is increased, the resonant frequency of an LC circuit A. decreases B. increases C. doesn’t change

D.

This is impossible to determine.

591. In a low Q parallel resonant circuit, when XL = XC A. IL = IC C. IC is less than IL B. IC

IL is less than IC

D.

IL is more than

592. To double the resonant frequency of an LC circuit with a fixed value of L, the capacitance, C, must be A. doubled B. quadrupled C. reduced by one-half D. reduced by one-quarter 593. A higher Q for a resonant frequency provides a A. dampened response curve B. wider bandwidth C. narrower bandwidth D. none of the above 594. The Q of a parallel resonant circuit can be lowered by A. placing a resistor in parallel with the tank B. adding more resistance in series with the coil C. decreasing the value of L or C D. both A and B 595. The ability of an LC circuit to supply complete sine waves when the input to the tank is only a pulse is called A. tuning C. anti-resonance B.

the flywheel effect

D.

its Q

596. Which of the following can provide a higher Q? A. a higher L/C ratio B. a lower L/C ratio C. more resistance in series with the coil D. either B or C 597. A resonance curve for a series circuit is a plot of frequency versus ____. A. voltage C. current B. impedance D. reactance 598. At half-power points of a resonance curve, the current is ____ times the maximum current. A. 2 C. √𝟐 B. 1/√2 D. 1/2 599. A parallel resonant circuit can be used A. to amplify certain frequencies B. to reject a small band of frequencies C. as a high impedance D. both B and C 600. As the Q-factor of a circuit ____, its selectivity becomes ____. A. increases, better C. decreases, better B. increases, worse D. decreases, narrower

601. The half – power frequency of, series RC circuit is A. 1/RC C. R/C B. RC D. C/R 602. For the given parallel resonant circuit, match the following: A. I at resonance 1. W/R B. IL 2. In phase with voltage C. Dynamic impedance 3. L/CR 4. Lags the applied voltage ABC ABC A. 4 2 3 C. 4 2 1 B. 2 4 3 D. 2 4 1 603. To increase the Q- factor of an inductor, it can be with A. Thicker wire B. Thinner wire C. Longer wire D. Wire with heavy insulation 604. Given Z = jωL + 1/jωC; the magnitude of Z curve will be

A. Figure a B. Figure b above

C. D.

Figure c none of

605. The bandwidth of R.C series circuit is A. 1/RC C. ∞ B. RC D. none above

of

the

the

606. Consider the following statements: In a series RLC resonant circuit, the bandwidth is 1. directly proportional to resonant frequency 2. Inversely proportional to resonant frequency 3. directly proportional to quality factor 4. Inversely proportional to quality factor A. 2 & 3 are correct C. 1 & 3 are correct B. 2 & 4 are correct D. 1 & 4 are correct 607. An RLC parallel resonant circuit has a resonance frequency of 1.5 MHz and a bandwidth of 1 kHz. If C = 150 pF, then the effective resistance of the circuit will be A. 2.96 MΩ C. 9.5 Ω B. 14.75 Ω D. 4.7 Ω 608. The parallel RL circuit is having quality factor of Q1, when it is connected in series with R, the new quality factor Q2 will be A. Q2 > Q1 C. Q2 = Q1 B. Q2 < Q1 D. none of the above

609. In a series RLC circuit, as R increases 1. Bandwidth decreases 2. Bandwidth increases 3. Resonance frequency increases 4. Lower 3 dB decreases 5. Upper 3 dB increases A. 2, 4 & 5 are correct C. 2, 3, 4 are correct B. 1, 4 & 5 are correct D. none of the above

619. Find fR in the circuit shown.

610. In a series RLC circuit, given R = 10 Ω, L = 14 H, C = 1 F. Find damping ratio. A. 1.33 C. 0.5 B. 0.187 D. none of the above

620. The parallel RLC circuit shown is in resonance.

611. The power factor of parallel RLC circuit at W > Wo is A. < 1 C. > 1 B. =1 D. 0 612. The phase of even symmetric signal is A. +90° C. 0° B. –90° D. 0° or ±180° 613. The power in a series R-L-C circuit will be half of that at resonance when the magnitude of current is equal to A. V/2R C. V/√𝟐R B. V/√3R D. √2V/R 614. In a series RLC high Q circuit, the current peaks at a frequency A. f = fo C. f < fo B. f > fo D. none of these 615. The given series resonant circuit resonance at frequency of 20 MHz. It will A. By pass all signals of 20 MHz B. C. D.

permit flow of signal of 20 MHz along the time Not produce any effect at 20 MHz cause moderate attenuation of signal at 20 MHz

616. The half power frequency of series RL circuit is A. R/L C. 2R/L B. L/R D. 2L/R

A. B.

all frequencies 0.5 rad/ sec

C. D.

5 rad / sec 1 rad/ sec

A.

|IR| < 1 mA

C.

|IR + IC| < 1 mA

B.

|IR + IL| >1 mA

D.

|IL + IC| > 1 mA

621. A series RLC ckt has a Q of 100 and an impedance of (100 + j0) Ω at its resonance angular frequency of 107 rad| sec. The values of R & L are A. R = 100 Ω; L = 1 mH C. R = 100 Ω; L = 10 mH B. R = 10 Ω; L = 10 mH D. none of the above 622. The parallel RLC circuit having damping ratio δp is connected in series with same values, then series circuit damping ratio δs is A. 4δp C. δp/4 B. 2δp D. δp/2 623. A series LCR circuit consisting of R = 10Ω, |XL| = 20 Ω & |XC| = 20 Ω is connected across an a.c supply of 200 V rms. The rms voltage across the capacitor is A. 200∠-90° C. 400∠+90 B. 200∠+90° D. 400∠-90 624. At fR what is K?

A. B.

0.25 0.5

C. D.

0.999 1.0

C.

2Ω

625. Find Zin at resonance.

617. In a series RLC circuit, the value of current at resonance is affected by the value of A. only L C. both L & C B. only C D. only R 618. In a series RLC circuit at resonance with Q = 10, and with applied voltage of 100 mV at resonance frequency voltage across capacitor is A. 100 mV C. 10 mV B. 1 volt D. 10 volts

A.

1.28 Ω

B.

12.8 Ω

D.

128 Ω

626. For the series RLC circuit, the partial phasor diagram at a certain frequency is shown, the operating frequency of the circuit is

A. B. C. D.

Equal to resonant frequency less than resonant frequency Greater than resonant frequency none of the above

627. In a series RLC circuit at resonance, the magnitude of the voltage developed across the capacitor A. is always zero B. can never be greater than the input voltage C. can be greater than the input voltage however, it is 90° out of phase with the input voltage D. can be greater than the input voltage and is in phase with the input voltage. 628. A series RLC circuit when existed by a 10 V sinusoidal voltage source of variable frequency, exhibits resonance at 100 HZ and has a 3dB band width of 5 Hz. The voltage across the inductor L at resonance is A. 10 V C. 10/√2 V B. 10√2 V D. 200 V 629. A circuit with a resistor, inductor and capacitor in series is resonant at fR Hz. If all the component values are now doubled, the new resonant frequency is A. 2 fR C. fR/4 B. still fR D. fR/2 630. A coil (series RL) has been designed for high Q performance at a rated voltage and a specific frequency. If the frequency of operation is doubled, and the coil is operated at the same rated voltage, then the Q factor and the active power P consumed by the coil will be affected as follows A. P is doubled, Q is halved B. P is halved, Q is doubled C. P remain constant, Q is doubled D. P decreases 4 times, Q is doubled 631. A series RLC circuit has the following parameter values R = 10 Ω, L = 0.01 H, C = 100 µF. The Q factor of the circuit at resonance is A. 1 C. 0.1 B. 10 D. none of the above 632. At resonance, the parallel circuit of given figure constituted by an iron-cored coil and a capacitor, behaves like.

A. open circuit =R B. short >R

C.

pure resistance

D.

pure resistance

633. Find L & C of a parallel RLC circuit to resonate at 1 rad/sec with a Q of 5 and resistance of 1 ohm. A. 1/5 H, 5 F C. 1 H, 1 F B. 5 H, 1/5 F D. 5 H, 5 F 634. In a parallel RLC resonant circuit R = 10 kΩ, C = 0. 47 µF, the bandwidth will be. A. 212.76 rad/sec C. 100 rad/sec B. 2.12 x 1010 rad/sec D. none of the above 635. A parallel resonate circuit (RP, L, &C) and a series resonant circuit (RS, L & C) have the same Q. Find the relation between RP & RS A. RS = Q2Rp C. RP = RS B. RP = Q2RS D. none of the above 636. In a parallel resonant circuit, as R increases, the selectivity will be A. Decreasing C. Constant B. Increasing D. none of the above 637. In a series RLC circuit, the phasor form at some frequency is as shown, then the frequency is

A. B. C. D.

Less than W0 More than W0 equal to W0 none of the above

638. In a series RLC circuit, let Qc be the Q of the coil at resonance and let Qs = (resonance frequency)/bandwidth, then A. Qc and Qs are not related to each other B. C. D.

Qc > Qs Qc < Qs Qc = Qs

639. A coil is represented by an inductance L in parallel with a resistance R. The Q of the coil at frequency w is A. R/(ωL) C. ωLR

B.

ωL/ R

D.

1/(ωLR)

640. The half power bandwidth of a series RCL circuit is A. R/L C. 1/RC B. L/RC D. ω0L/R 641. The Q of a parallel RLC circuit at its resonance frequency ω0 is A. ω0L/R C. ω0RC B. R/ω0C D. ω0LR 642. In a series R-L-C circuit below resonance, the current A. lags behind the applied voltage B. leads the applied voltage C. is in phase with the voltage D. leads or lags behind the applied voltage depending upon the actual values of L and C 643. A high Q coil has A. large bandwidth B. high losses

C. D.

low losses flat response

644. At a frequency below the resonant frequency ____ circuit is capacitive and ____ circuit. A. series, parallel C. parallel, parallel B.

parallel, series

D.

series, series

645. In the following parallel circuit, resonance will never occur, if:

A. B. C. D.

R12 = R22 = L/C R12 < L/C R22 > L/C and R12 < L/C R12 > L/C and R22 > L/C

646. The circulating current in a parallel LC circuit at any resonant frequency is A. Directly proportional to frequency B. Inversely proportional to frequency C. Independent of frequency D. none of the above 647. In series RLC circuit excited by a voltage, e = E sin ωt, where LC < (1/ω2) A. Current lags the applied voltage B. current leads the applied voltage C. current is in phase with the applied voltage D. voltages across L and C are equal 648. A series RLC circuit has a resonance frequency of 1 kHz and a quality factor Q = 100. If each of R, L and C is doubled from its original value, the new Q of the circuit is A. 25 C. 100 B. 50 D. 200

649. What is the bandwidth of parallel RLC circuit at resonance? A. RC C. R/C B. 1/RC D. C/R 650. The current bandwidth of RC series circuit is A. 1/RC C. ∞ B. RC D. none of above

the

651. The circuit shown acts as an ideal current source with respect to terminals AB, when the frequency is

A. B.

zero 1 rad/sec

C. D.

4 rad/sec 16 rad/sec

652. A series RLC circuit is excited by an ac voltage v(t) = sin t. If L = 10 H and C = 0.1 F, then the peak value of the voltage across R will be A. 0.707 B. 1 C. 1.414 D. indeterminate as the value of R is not given 653. In a parallel RLC circuit, the current source (I) lags voltage across circuit (V) if A. wL > 1/wC C. R > [wL + 1/wC] B. wL < 1/wC above

D.

none

of

the

654. At lower half power frequency the total reactance of the series RLC circuit is A. –R C. √2𝑅∠-45° B. √2𝑅∠45° D. none of the above 655. In a parallel RLC circuit, the quality factor at a resonance is given by A. R√𝐿/𝐶 C. 1/R√𝐿/𝐶 B. R√𝐶/𝐿 D. 1/R√𝐂/𝐋 656. A practical inductor can be replaced by the following equivalent circuit at low to medium frequency.

A. B.

Figure a Figure b

C. D.

Figure c Figure d

657. A coil of wire has inductive impedance. At high frequencies the impedance will be represented by

A. B.

10, 1 10, 2

E. CORRECTION (1-PHASE)

A. B.

Figure a Figure b

C. D.

Figure c Figure d

658. In a series RLC circuit R= 2 kΩ, L = 1 H, and C = 1/ 400 microfarads. The resonant frequency is A. 2 x 104 Hz C. 104 Hz 4 B. (1/π) x 10 Hz D. 2π x 104 Hz 659. In the circuit shown in the figure, Vs = Vm sin 2t and Z2 = 1 – j. The value of C is shown such that the current I is in phase with Vs. The value of C in farad is

A. B.

1/4 1/2√2

C. D.

2 4

660. The circuit shown has i(t) = 10 sin (120πt). The power (time average power) dissipated in R is when L = 1/120π H, C = 1/60π H, R = 1 ohm.

A. B.

25 watts 100 watts

C. D.

10/√2 watts 50 watts

661. The value of the capacitance C in the given ac circuit to make it a constant resistance circuit or for the supply current to be independent of its frequency is

A. B.

1/16 F 1/12 F

C. D.

1/8 F ¼F

662. A parallel RLC circuit has half power frequencies at 105 M rad/s and 95 M rad/s. Then Q is given by A. 10.5 C. 100 B. 9.5 D. 10 663. The system function H(s) = s/(s2 + 2s + 100). The resonant frequency and the bandwidth in rad/s are given, respectively, by

C. D.

100, 2 100, 1

POWER FACTOR

664. EE Board Exam October 1990 A single phase inductive load takes 50 kVA at 0.60 power factor lagging. Solve for the kVAR of a capacitor required to improve the power factor to 1.0. A.

30 kVAR

C.

22.5 kVAR

B.

20 kVAR

D.

40 KVAR

665. REE Board Exam March 1998 A single phase induction motor is rated 5 hp, 75% power factor and 220 volts. What approximate size of capacitor is necessary to raise the power factor to about 95%? A.

3 kVAR

C.

2.5 kVAR

B.

2 kVAR

D.

3.5 Kvar

666. EE Board Exam April 1984 A plant has a load of 290 kilowatt with an average power factor of 70%. The owner requests you to correct the power factor to reduce its power consumption. How much capacitor kVAR is required to increase the power factor to 90%? A.

152.46

C.

150.34

B.

155.39

D.

154.58

667. REE Board Exam October 1996 A single-phase, 60 Hz, 5 hp squirrel cage induction motor draws a current of 53 A at 117 V. If it has a 78.5% electrical to mechanical conversion efficiency, what capacitance should be connected at the terminals of the motor in order to increase the power factor of the load combination to 92%? A.

480 μF

C.

320 μF

B.

380 μF

D.

420 μF

668. EE Board Exam April 1997 A load of 10,000 kVA, 80% pf lagging is connected to a 13,200 volts line. How much capacitive reactive power is needed to correct the power factor to 0.97 lagging? A. 5,156 kVAR C. 2,547 kVAR B. 3,138 kVAR D. 4,395 kVAR 669. In a pure reactive circuit, the power factor is A. lagging C. leading B. zero D. unity 670. Power factor is defined as the ratio of

A. B. C. D.

volt ampere to watts watts to volt amperes volt amperes reactive to watts watts to volt amperes reactive

671. In a series circuit consisting of resistance and reactance, power factor is defined as the ratio of A. resistance to impedance B. resistance to reactance C. reactance to impedance D. none of these 672. For a parallel circuit consisting of resistance and reactance the value of power factor is the ratio of A. impedance to reactance B. reactance to impedance C. resistance to impedance D. impedance to resistance 673. It is not easy to find the value of impedance for a parallel circuit but power factor can easily be obtained as a ratio of A. active current to line current B. reactive current to line current C. line current to active current D. none of these 674. The power factor of a.c. circuit containing both a resistor and a conductor is A. more than unity C. between 0 -1 leading B. leading by 90° D. none of these 675. In an a.c. circuits, a low value of reactive voltampere compared with watts indicates A. high power factor C. leading power factor B. unity power factor D. none of these 676. In a given circuit when power factor is unity the reactive power is A. a maximum C. zero B. equal to I2R D. none of these 677. The capacitor of power factor correction are rated in terms of A. voltage C. kW B. VA D. kVAR 678. Poor power factor results in all of the following except A. overloading of transformers B. overloading of alternators C. reduction in power losses D. reduction in load handling capacity of electrical system 679. Power factor of an inductive circuit can be improved by connecting a capacitor to it in A. series B. parallel C. either series or parallel D. depends on the value of the capacitor

680. For will A. B. C. D.

the same load, if the power factor is reduced, it draw more current draw less current draw same current but less power draw less current but more power

681. The power factor of incandescent bulb is A. 0.8 lagging C. unity B. 0.8 leading D. zero 682. Power factor of the magnetizing component of a transformer is A. unity C. always leading B. 0.8 lagging D. zero 683. One of the reasons for improving the power factor is A. to increase the reactive power B. to decrease the reactive power C. to increase the real power D. to decrease the real power 684. Another reason for improving the power factor is A. to avoid poor voltage regulation B. to keep voltage regulation constant C. to increase the voltage regulation D. to decrease the voltage regulation 685. Power factor improvement may be achieved by the use of A. synchronous motor C. long transmission line B. induction motor D. short transmission line 686. The advantage of using static capacitor to improve the power factor is because they A. are not variable B. are almost loss free C. provide continuous change of power factor D. none of these 687. Many industrial tariffs penalize consumers whose power factor falls A. below 0.8 C. between 0.8 to 0.95 B. below unity D. none of these 688. A factory takes a load of 1000 KW and has a reactive power of 1000 KVAR. Its power factor is A. 0.6 C. 0.8 B. unity D. 0.7 689. A current of 10 amperes at a power factor of 0.8 lagging is taken from 250 V a.c. supply. The reactive power of the system is A. 2000 watts C. 1500 watts B. 2000 VA D. 1500 VAR 690. A resistance ‘R’ Ω and inductance ‘L’ H are connected across 240 V, 50 Hz supply. Power dissipated in the circuit is 100 W and the voltage across R is 100 V. In order to improve the pf to unity,

B.

106 μF

D.

6.33 μF

F. AC NETWORK ANALYSIS 692. A segment of a circuit shown in given figure VR = 5 V, VC = 4 sin 2t. The voltage VL is given by A. 3 – 8 cos 2t B. 32 sin 2t C. 16 sin 2t D. 16 cos 2t

A. B.

j10 Ω

A. B. C. D.

0° 45°

C. D.

-45° -90°

695. Consider the following statements: In the circuit shown in the figure, if the equivalent impedance x – x is Zeq then I2

4Ω

j10 Ω

j4 Ω

x

1. Zeq = 2 + j5 2. Zeq = 2 + j3 Of these statements

the

j2 Ω

j5.33 V 5.33 V

j4 Ω

C. D.

-j5.33 V j3.33 V

1Ω + 1Ω

e2(t)

3. 4.

I1 = -I2 I1 = I2

-

cos 𝜔𝑡 V sin(𝜔𝑡 + 30°) + cos(𝜔𝑡 + 30°) V 𝟏∠𝟗𝟎°V j1 V

698. If all elements in a particular network are linear, then the superposition theorem would hold when the excitation is A. dc only C. either ac or dc B. ac only D. an impulse 699. For the network shown in given figure, the Thevenin equivalent impedance across terminals CD is given by A.

j10 Ω

of

B

-

V2

4Ω

j3 Ω

A

e1(t)

10 Ω

I1

none

+

I

x

D.

696. For the network shown in the figure, the voltage V B will be

1Ω

694. The phase angle of the current ‘I’ with respect to the V1 in the circuit shown in the figure is V1 = 100 (1 + j); V2 = 100(1 – j)

A. B.

2 and 3 are

697. In the circuit shown in given figure, 𝑒1 (𝑡) = √3 cos(𝜔𝑡 + 30°) and 𝑒2 (𝑡) = √3 sin(𝜔𝑡 + 60°). What is the voltage v(t) across the 1 ohm grounded resistor?

693. Three currents i1, i2 and i3 are approaching a node. If i1 = 10 sin (400t + 60°) A and i2 = 10 sin (400t - 60°) A, then i3 is A. 0 C. -10 sin 400t A B. 10 sin 400t A D. −5√3(3 sin 400𝑡)A

V1

C.

2A

691. What size of condenser must be placed across an inductance having a resistance of 10 ohms and reactance of 20 ohms to draw minimum current from the line when the combination is connected across a 60-cycle line? (Assume a condenser of negligible resistance). A. 20 μF C. 10 μF

A. 1 alone is true correct B. 2 and 4 are correct above

1A

the capacitor that is to be connected in series should have a value of A. 43.7 μF C. 437 μF B. 4.37 μF D. 4.37 mF

𝒁𝑻𝑯 =

𝑍1 +𝑍2 +𝑍2 𝑍3 𝑍1 +𝑍2 +𝑍3 +𝑍4

B.

𝑍𝑇𝐻 =

𝑍3 +(𝑍1 +𝑍2 4)

𝒁𝟏 𝒁𝟐 +𝒁𝟑 ] 𝒁𝟏 +𝒁𝟐 𝒁𝟏 𝒁𝟐 𝒁𝟒 +𝒁𝟑 + 𝒁𝟏 +𝒁𝟐

C.

𝑍𝑇𝐻 =

𝑍3 𝑍2 +𝑍1 ] 𝑍3 +𝑍2 𝑍 𝑍 𝑍1 +𝑍4 + 3 2 𝑍3 +𝑍2

D.

𝑍𝑇𝐻 =

𝒁𝟒 [

𝑍4 [

𝑍1 +𝑍2 +𝑍3 +𝑍4

700. In the given figure 𝑍1 = 10∠ − 60°, 𝑍2 = 10∠ − 60°,𝑍3 = 50∠53.13°. Thevenin impedance seen from X-Y is A. 𝟓𝟔. 𝟔∠𝟒𝟓° C. 70∠30° B. 60∠30° D. 34.4∠65° 701. In the figure the current source is 1∠0° A, R = 1 ohm, the impedances are ZC = -j ohm, and ZL = j2 ohm, The Thevenin equivalent circuit looking into the circuit across X-Y is

A. √2∠0° V, (1 + j2) Ω Ω B. 2∠45° V, (1 + j2) Ω j) Ω

C.

2∠45° V, (1 + j)

D.

√𝟐∠𝟒𝟓° V, (1 +

702. The circuit shown in Fig. 1 is replaced by its Norton’s equivalent circuit in Fig. 2. The value of I will be A. 2.5∠45° A C. 10∠ − 90° A B. 𝟓∠𝟗𝟎° A D. 15∠ − 45° A 703. Consider the following statements: The transfer impedance and admittance of a network remain constant when the position of excitation and response are interchanged if the network 1. is linear 2. consists of bilateral elements 3. has high impedance or admittance as the case may be 4. is resonant Of these statements A. 1 and 2 are correct C. 2 and 4 are correct B. 1, 3 and 4 are correct D. all are correct 704. In a linear network, the ratio of voltage excitation to current response is unaltered when the position of excitation and response are interchanged. The assertions stems from the A. principle of duality B. reciprocity theorem C. principle of superposition D. equivalence theorem 705. A certain network N feeds a load resistance as shown in Fig. 1. It consumes a power of ‘P’. If an indicated network is added as shown in Fig. 2. The power consumed by R will be A. less than P C. between P and 4P B. equal to P D. more than 4P 706. In the circuit shown in the figure, the current source I = 1 A, the voltage source V = 5 V, R1 = R2 = R3 = 1 Ω, L1 = L2 = L3 = 1 H, C1 = C2 = 1 F. The currents (in A) through R3 and the voltage source V respectively will be A. 1, 4 C. 5, 2 B. 5, 1 D. 5, 4 707. For loop (1) of the network shown in the given figure, the correct loop equation is A. C. B. D. 708. An ac source of voltage ES and an internal impedance of ZS = (RS + jXS) is connected to a load of impedance ZL = (RL + jXL). Consider the following conditions in this regard. 1. XL = XS if only XL is varied 2. XL = -XS if only XL is varied 3. 𝑅𝐿 = √𝑅𝑆2 + (𝑋𝑆 + 𝑋𝐿 )2 if only RL is varied

4.

|ZL| = |ZS| if the magnitude of ZL is varied, keeping the phase angle fixed Among these conditions, those which are to be satisfied for maximum power transfer from the source to the load would include A. 2 and 3 C. 1, 2 and 4 B. 1 and 3 D. 2, 3 and 4 709. Under the conditions of maximum power transfer from an ac source to a variable load A. the load impedance must be inductive, if the generator impedance is inductive B. the sum of the source and the load impedances is zero C. the sum of the source reactance and the load reactance is zero D. the load impedance has the same phase angle as the generator impedance 710. If the combined generator and line impedance is (5 + j10) Ω, then for the maximum power transfer to a load impedance from a generator of constant generated voltage, the load impedance is given be which of the following? A. (5 + j10) Ω C. (5 + j5) Ω B. (5 – j10) Ω D. 5 Ω 711. A voltage source having an internal impedance of 8 + j6 Ω supplies power to a resistive load. What should be load resistance for maximum power transferred to it? A. 8 Ω C. 10 Ω B. 6 Ω D. √10 Ω 712. The Thevenin equivalent circuit of a network is as shown in the given figure. For maximum power transfer to the variable and purely resistive load R L, its resistance should be A. 60 Ω C. 100 Ω B. 80 Ω D. infinity 713. Two ac sources fed a common variable load as shown in the given figure. Under the maximum power transfer condition, the power absorbed by the load resistance RL is A. 2200 W C. 1000 W B. 1250 W D. 625 W 714. REE Board Exam March 1998 Three impedances, -j10, j10 and 10 ohms are wyeconnected. Determine the impedance of an equivalent delta. A.

12.5, j12.5, -12.5 Ω

C.

j8.5, -j12.5, 8 Ω

B.

10, j10, -j10 Ω

D.

5, j5, -j5 Ω

715. A telephone circuit makes power available at a pair of terminals. The open circuit voltage across the terminals is 1 volt and the impedance looking into the terminals is 500 – j500 Ω. What is the maximum power that can be drawn from the circuit? A. 0.002 W C. 0.001 W

B.

0.0005 W

D.

0.0014 W

G. BALANCED POLYPHASE SYSTEM 716. REE Board Exam April 2002 In a balanced three-phase system, the phase A voltage is 132.8 cis 0°, what is the line to line voltage VCA? A.

230 cis 30°

C.

230 cis (-60°)

B.

230 cis (-30°)

D.

132.8 cis 120°

717. REE Board Exam September 2001 The phase B line voltage and the phase A line current of a balanced three phase system are v = 220 sin (ωt + 210°) and i = 10 sin (ωt + 180°) amperes, respectively. What is the power of the system? A.

1,905 W

C.

5,716 W

B.

3,300 W

D.

3,810 W

718. REE Board Exam April 1997 A 170 kV, 3-phase electric source delivers 200 MVA to a balanced load, which has a power factor of 90% lagging. What is the line current? A. 257 A C. 402 A B. 502 A D. 679 A 719. REE Board Exam October 1997 A three-phase motor is rated 50 hp, 440 volts and 85% power factor. What is its rated current? A.

61.5 A

C.

55 A

B.

57.5 A

D.

59 A

720. EE Board Exam April 1985 A balanced 3-phase load draws 120 amperes line current at 230 volts line to line, 0.848 pf lagging. Solve for the real power. A.

40.54 kW

C.

41.45 kW

B.

42.35 kW

D.

43.15 kW

721. REE Board Exam March 1998 A generator supplies three-phase power to balanced load. The voltage is 230 volts, the current is 18 A and the power factor is 85%. What is the power? A.

3.6 kW

C.

6.1 kW

B.

1.6 kW

D.

1.4 kW

722. EE Board Exam April 1984 A balanced 3-phase load draws 75 amperes line current at 230 volts line to line, 0.848 pf lagging. Solve for the reactive power being drawn.

A.

15.83 kVAR

C.

15.35 kVAR

B.

15.26 kVAR

D.

15.94 kVAR

723. EE Board Exam April 1990 The input power factor to a three-phase, 6-poles, 460 volts., 60 Hz, 50 hp induction motor is 0.62 as 20 A is drawn by the motor. Find the power input to the motor. A.

9,880 W

C.

9,895 W

B.

9,675 W

D.

9,478 W

724. EE Board Exam April 1992 A 460 volt, three-phase motor draws 208 A with a power factor of 0.91 lagging. Calculate the kW input to the motor. A.

150.8

C.

152.4

B.

156.3

D.

160.3

725. EE Board Exam April 1993 A wye-connected load has a 5∠20° ohm impedance per phase and is connected across a 120-V threephase source. Calculate the line current. A.

24 A

C.

41.56 A

B.

13.85 A

D.

15.45 A

726. EE Board Exam April 1993 Three condensers, each having capacity of 75 microfarads are connected in star to a 440 volts, 3phase, 50 cycles supply. Calculate the capacitance of each of the three condensers so that when they are connected in delta to the same supply the line current remains the same. A.

20 μF

C.

25 μF

B.

28 μF

D.

30 μF

727. EE April 1993 A balanced three-phase load is wye-connected and has an impedance Zp = 4 – j3 ohms per phase. Find the line current if this load is connected across a 220 V three-phase source. A.

25.4 A

C.

20.5 A

B.

22.3 A

D.

26.7 A

728. REE Board Exam October 1998 Three 10-ohm resistances are connected delta on a balanced three-phase source. If the equation of the phase Van =120 sin ωt. What is the equation of the line current in line a?

A. 20.78 sin (ωt + 30°) 56.56°)

C.

12 sin (ωt –

B.

D.

36 sin ωt

13.15 sin (ωt - 30°)

729. EE Board Exam October 1994 Three resistors 10, 15 and 30 ohmic values are connected in wye-configuration to a balanced 208 volt three-phase supply. Calculate the total power of the system. A. 2644 W C. 3080 W B. 2880 W D. 3280 W 730. REE Board Exam March 1998 Three impedances each 10 + j5 ohms are connected delta on a balanced three-phase source. If the equation of the phase Van =120 sin ωt. What is the equation of the line current through the impedance connected across phase A and B? A. C. 56.56°)

20.02 sin (ωt - 22°) 16.21 sin (ωt +

B. 3.44°) 8.15°)

18.59 sin (ωt + D. 21.32 sin (ωt –

731. EE Board Exam June 1990 Two parallel connected loads A and B are supplied by a 440 V, 3-phase, 60 Hz generator. Load A draws an apparent power of 100 kVA at 0.80 pf lagging and load B draws an apparent power of 70 kVA at unity pf. Determine the feeder current. A.

208 A

C.

214 A

B.

212 A

D.

202 A

732. EE Board Exam April 1990 A three-phase motor takes 10 kVA at 0.67 pf lagging from a source of 230 volts. It is in parallel with a balanced delta load having 16 ohms resistance and 12 ohms capacitive reactance in series in each phase. Determine the total power factor. A.

0.966 lagging

C.

0.917 lagging

B.

0.896 lagging

D.

0.967 lagging

733. REE Board Exam March 1998 The phase b line voltage and the phase a line current of a balanced three-phase system are v = 220 (sin wt + 210) and i = 10 sin (wt - 30), respectively. What is the power of the system? A.

1905 W

C.

5716 W

B.

3300 W

D.

3810 W

734. EE Board Exam April 1985 A balanced 3-phase load draws 120 amperes line current at 230 volts line to line, 0.848 pf lagging current. Solve for the readings of the two wattmeters used to measure the 3-phase power. A.

25.543 kW, 15.087 kW

B.

28.155 kW, 12.385 kW

C.

24.365 kW, 16.175 kW

D.

27.583 kW, 12.957 kW

735. EE Board Exam April 1988 MERALCO used two wattmeters to measure the balanced 3-phase dynatron elevator motor drive. The coils of the wattmeters are connected to the current transformers, which are lines 1 and 2 respectively. The potential coils are connected to potential transformers, which are across lines 2 and 3 and lines 3 and 1, respectively. The line potentials are 230 V and the line currents are each 150 A. The wattmeters each indicate 19.6 kW. Assume load is wye connected. What is the total power supplied? A.

49.175 kW

C.

45.461 kW

B.

48.236 kW

D.

47.350 kW

736. EE Board Exam April 1992 A 460-volt three-phase motor draws 208 A with a power factor of 0.91 lagging. Calculate the indication of W1 and W2 for the given condition. A. 75.40 kW, 75.40 kW 61.25 kW

C.

89.56 kW,

B. 91.23 kW, 59.58 kW 55.57 kW

D.

95.24 kW,

737. EE Board Exam June 1990 Two wattmeter method is used to test a 25 HP, 230 volt, 1800 rpm, 60 cycle, 3-phase induction motor. When the line voltages are 230 volts, one wattmeter reads +13,400 watts and the other +7,400 watts. Determine motor power factor. A.

0.961

C.

0.894

B.

0.886

D.

0.807

738. In a balanced three phase star connected circuit the line voltages are equal A. to the line current B. to the phase voltage C. and so are line currents D. but the line currents are unequal 739. The type of a.c. distribution system commonly used to supply both light and power is the A. open delta system B. three phase delta system

C. D.

three phase star system with neutral wire three phase star system without neutral wire

740. The phase displacement between phasors in polyphase system is always A. 90 degrees B. 120 degrees C. 360 degrees divided by the number of phases D. none of the above 741. In a balanced three phase star connected system the line voltage is A. the phasor difference of the two phase voltages B. the phasor sum of the two phase voltages C. 0.707 times the phase voltage D. 1.414 times the phase voltage 742. In a star connected system line current is A. 0.707 times the phase current B. 1.735 times the phase current C. equal to the phase current D. 1.414 times the phase current 743. The advantages of star connections over delta connections for the same voltage is that it gives A. step down current B. extra step up voltage C. extra step up current D. extra step up power 744. Power in a three phase star system is equal to A. √3 x VL x IL x power factor B. 3 x Vph x IL x power factor C. √3 x VL X Iph X power factor D. 3 x Vph x Iph x power factor 745. Power in a three phase delta system with balanced load is equal to A. √𝟑 x VL x IL x power factor B. √3 x Vph X Iph X power factor C. 3 x Vph x IL x power factor D. 3 x VL x IL x power factor 746. In a delta connected system the line current is A. 1.414 times the phase current B. phasor sum of the two phase currents C. equal to the phase current D. 1.732 times the phase current 747. Power in star connected system is A. equal to that of delta system B. √2 times the delta system C. √3 times the delta system D. 3 times of a delta system 748. Electric power is almost exclusively generated, transmitted and distributed, by three phase system because it A. it is more efficient B. uses less material for a given capacity C. costs less than single-phase apparatus D. all of the above

749. The voltages induced in the three windings of a three-phase alternator are ____ degree apart in time phase. A. 120 C. 90 B. 60 D. 30 750. If positive phase sequence of a 3 – phase load is ab-c the negative sequence would be A. b-a-c C. a-c-b B. c-b-a D. all of the above 751. In the balanced 3-phase voltage system generated by a Y-connected alternator, VYB lags ER by ____ electrical degrees. A. 90 B. 120 C. 60 D. 30 752. The power taken by 3-phase load is given by the expression A. 3 VL IL cos φ C. 3 VL IL sin φ B. √𝟑 VL IL cos φ D. √3 VL IL sin φ 753. In a balanced 3-phase voltage difference phase voltages reach values ____ degree apart. A. 120 C. B. 60 D.

generator, the their maximum 240 30

754. If the B-phase, Y-connected alternator become reverse connected by mistake, it will not affect. A. V Y B C. V B R B. V R Y D. V B Y 755. Three equal impedances are first connected in star across a balanced 3-phase supply. If connected in delta across the same supply. A. phase current will be tripled B. phase current will be doubled C. line current will become one-third D. power consumed will increase three-fold 756. A 3-phase, 4-wire, 230/440-V system is supplying lamp load at 230 V. If a 3-phase motor is now switched on across the same supply then, A. neutral current will increase B. all line currents will decrease C. neutral current will remain unchanged D. power factor will be improved 757. Power factor improvement A. does not affect the performance characteristics of the original load B. employs series resonance C. increase the active power drawn by the load D. increases the reactive power taken by the load 758. The chief disadvantage of a low power factor is that A. more power is consumed by the load B. current required for a given load power is higher C. active power developed by a generator exceeds its rated output capacity D. heat generated is more than the desired amount

761. Phase reversal of a 4-wire unbalanced load supplied from a balanced 3-phase supply changes A. magnitude of phase currents B. magnitudes as well as phase angle of neutral current C. the power consumed D. only the magnitude of neutral current 762. In a two-phase generator, the electrical displacement between two phase or windings is ____ electrical degrees. A. 120 C. 180 B. 90 D. none of the above 763. In a six-phase generator, the electrical displacement between different phases or windings is ____ electrical degrees. A. 60 C. 120 B. 90 D. 45 764. The torque on the rotor if a 3-phase motor is more constant than that of a single motor because A. single phase motors are not self-starting B. single phase motors are small in size C. 3-phase power is of constant value D. none of the above 765. For the same rating, the size of a 3-phase motor will be ____ single phase motor. A. less than that of C. same as that of B. more than that of D. none of the above 766. To transmit the same amount of power over a fixed distance at a given voltage, the 3-phase system requires ____the weight of copper required for the single-phase system. A. 3 times C. 1.5 times B. 3/4 times D. 0.5 times 767. The phase sequence of a three-phase system is RYB. The other possible phase sequence can be A. B R Y C. R B Y B. Y R B D. none of the above

R

60 W

Y

60 W

L1

L2

C B Fig. 14.1

A. B. C. D.

L1 will burn more brightly than L2 L2 will burn more brightly than L1 both lamps will be equally bright none of the above

769. If the phase sequence of the 3-phase line in Fig 14.1 is reversed

3-phase line

760. When phase sequence at the 3-phase load is reversed A. phase powers are changed B. phase currents are changed C. phase currents change in angle but not in magnitude D. total power consumed in changed

3-phase line

768. If in Fig. 14.1, the phase sequence is RYB, then 759. In the 2-wattmeter method of measuring 3-phase power, the two wattmeter’s indicate equal and opposite readings when load power factor angle is ____ degrees lagging. A. 60 C. 30 B. 0 D. 90

R

60 W

Y

60 W

L1

L2

C B Fig. 14.1

A. B. C. D.

L1 will be brighter than L2 L2 will be brighter than L1 both lamps will be equally bright none of the above

770. The advantage of star-connected supply system is that A. line current is equal to phase current B. two voltages can be used C. phase sequence can easily be changed D. it is a simple arrangement 771. In a balanced star connected, line voltages are ____ ahead of their respective phase voltages. A. 30 C. 120 B. 60 D. none of the above 772. In a star-connected system, the relation between the line voltage VL and phase voltage Vph is A. 𝑉𝐿 = 𝑉𝑝ℎ C. 𝑽𝑳 = √𝟑𝑽𝒑𝒉 B. 𝑉𝐿 = 𝑉𝑝ℎ /√3 D. none of the above 773. Fig 14.2 shows a balanced star-connected system. The line voltage VRY is given by

R N B

EYN

EBN

777. The power delivered by the 3-phase system shown in Fig. 14.2 is √3VL IL cos θ. Here θ is the phase difference between

IR

ERN

Y

VRY VBR

IY IB

R N B

Fig. 14.2 A. B. C. D.

R IR

ERN N B

EYN

EBN

Y

VRY VBR

IY IB

VYB

Fig. 14.2 A. B.

30 + ϕ 30 - ϕ

C. D.

60 + ϕ 120 – ϕ

775. If the load connected to the 3-phase generator shown in Fig. 14.2 has a leading p.f. of cos , then angle between VRY and IR is

Y

N

VYB

778. A 3-phase load is balanced if all the three phases have the same A. impedance B. power factor C. impedance and power factor D. none of the above 779. Three 50-ohm resistors are connected in star across 400 V, 3-phase supply. If one of the resistors is disconnected, then line current will be A. 8 A C. 8√3 A B. 4 A D. 8/√3 A 780. Fig. 14.3 shows a balanced delta-connected supply system. The current in line 1 is

IR

EYN

EBN

Y

1

IB IR

VRY VBR

IY

2 B

IB

IY

VYB

90 – ϕ 90 + ϕ

C. D.

60 + ϕ 30 - ϕ

R N EBN

EYN Y

VBR

IY IB

3

IR - IB..... phasor difference IB - IR ….. phasor difference IY - IR - IB ….. phasor difference none of the above

781. In Fig. 14.3, line currents are ____ behind the respective phase currents.

R

VRY

VYB

1

IB IR

2 B IY

Fig. 14.2 VRY = 230 V VRY > 230 V

A. B. C. D.

IR

ERN

Y Fig. 14.3

776. Each phase voltage in Fig. 14.2 is 230 V. If connections of phase B are reversed then

A. B.

IB

line voltage and corresponding line current phase voltage and corresponding phase current phase current and line current none of the above

Fig. 14.2

B

VBR

R ERN

A. B.

VRY IY

Fig. 14.2 A. B. C. D.

R

B

EYN

EBN

VRY = ERN – ENY …..phasor sum VRY = ERN – EYN.....phasor difference VRY = ENR + EYN …..phasor sum none of the above

774. If the load connected to the 3-phase generator shown in Fig. 14.2 has a lagging p.f. of cos , then angle between VRY and IR is

IR

ERN

VYB

C. D.

VRY < 230 V VRY = 0 V

Y 3 Fig. 14.3

A. B. above

60 30

C. D.

120 none

of

the

787. If one of the resistors in Fig. 14.4 were opencircuited, then power consumed in the circuit is

782. The delta-connected generator shown in Fig. 14.3 has phase voltage of 200 V on no load. If a connection of one of the phases is reversed then resultant voltage across the mesh is

R

10 Ω

400 V

IR

Fig. 14.4

A. B. above

2 B

Y

IY

3

200 V 200√3 V

C. D.

400 V none of

8000 W 4000 W

C. D.

the

784. The resistance between any two terminals of a balanced star connected load is 12 . The resistance of each phase is A. 12  C. 6  B. 18  D. 36 

10 Ω

400 V

783. If one line conductor of a 3-phase line is cut, the load is then supplied by the ____ voltage. A. single phase C. three phase B. two phase D. none of the above

Fig. 14.4

A. B. above

2.5 A 1A

C. D.

400 V R

Y 400 V

10 Ω

B

R

N

Fig. 14.5 A. B. above

Fig. 14.4

A. B. above

400 V 𝟒𝟎𝟎√𝟐 V

C. D.

230 V none of

the

200 W 300 W

C. D.

10 Ω 10 Ω

400 V 400 V

8Ω

6Ω

400 V

8Ω

6Ω

400 V

8Ω

6Ω

400 V

10 Ω N

Fig. 14.6

Fig. 14.4

A. B.

4000 W 2300 W

345 W none of

C. D.

4600 W 5290 W

the

790. The power factor of the star-connected load shown in Fig. 14.6 is

786. The power rating of each resistor in Fig. 14.4 is

400 V

the

R

R

10 Ω

400 V

1.725 A none of

789. If one of the resistors in Fig. 14.5 is open-circuited, power consumption will be

400 V 10 Ω

10 Ω N

400 V

785. The voltage rating of each resistor in Fig. 14.4 should be

400 V

the

10 Ω

400 V

400 V

16000 W none of

788. The power consumed in the star-connected load shown in Fig. 14.5 is 690 W. The line current is

Fig. 14.3 A. B. above

10 Ω N

400 V

1

IB

10 Ω

400 V

A.

0.8 lagging

C.

0.75 lagging

B. above

0.6 lagging

D.

none

of

the

791. The voltage drop across each inductor in Fig. 14.6 is

8Ω

6Ω

400 V

8Ω

6Ω

400 V

8Ω

6Ω

Fig. 14.6 184 V 138 V

C. D.

400 V none of

the

792. The power consumed in each phase of the circuit shown in Fig. 14.6 is

8Ω

6Ω

400 V

8Ω

6Ω

400 V

8Ω

6Ω

4A

D.

36 A

797. Three delta-connected resistors absorb 60 kW when connected to a 3-phase line. If the resistors are connected in star, the power absorbed is A. 60 kW C. 40 kW B. 20 kW D. 180 kW 798. If a balanced delta load has an impedance of (6 + j9) ohms per phase, then impedance of each phase of equivalent star load is A. (6 + j9) ohms C. (12 + j18) ohms B. (2 + j3) ohms D. (3 + j4.5) ohms

400 V

A. B. above

B.

799. In order to measure power in a 3-phase,4-wire unbalanced load, the minimum number of wattmeters required would be A. 1 C. 4 B. 2 D. 3 800. A wattmeter measures ____ power. A. instantaneous C. reactive B. apparent D. average 801. In the circuit shown in Fig. 14.7, the phase sequence is RYB. If the load p.f. is cos  lagging, then reading of wattmeter W2 will be

400 V

W1

R

± ±

Z

IL

Fig. 14.6

N

the

793. Three identical resistances connected in star consume 4000 W. If the resistances are connected in delta across the same supply, the power consumed will be A. 4000 W C. 8000 W B. 6000 W D. 12000 W 794. Three identical resistances, each of 15 , are connected in delta across 400 V, 3-phase supply. The value of resistance in each leg of the equivalent star-connected load would be A. 15  C. 5  B. 7.5  D. 30 

W2

VL IL

± ±

Fig. 14.7

A. 𝑽𝑳 𝑰𝑳 𝐜𝐨𝐬(𝟑𝟎° − 𝝋) √3𝑉𝐿 𝐼𝐿 sin(30° + 𝜑) B. 𝑉𝐿 𝐼𝐿 cos(30° + 𝜑) √3𝑉𝐿 𝐼𝐿 cos(30° + 𝜑)

C. D.

802. If the p.f. of the load shown in Fig. 14.7 (phase sequence is RYB) is zero, then W1

R

± ±

IL

795. Three identical capacitances, each of 450 F, are connected in star. The value of capacitance in each phase of the equivalent delta-connected load would be A. 150 F C. 225 F B. 450 F D. 900 F

VL N IL

Y

Z

B

W2

796. Three identical resistances connected in star carry a line current of 12 A. If the same resistances are connected in delta across the same supply, the line current will be A. 12 A C. 8 A

IL

Y

B

Z

3174 W none of

Z

C. D.

Z

2300 W 4000 W

Z

A. B. above

VL

VL ± ±

Fig. 14.7

A. B. C.

W1 will read zero W2 will read zero both W1 and W2 will read zero

IL

D.

W1 and W2 will read equal and opposite

806. If capacitors of equal capacitance are shunted across each phase in Fig. 14.7, then

803. If the p.f. of the load (phase sequence is RYB) in Fig. 14.7 is unity, then

± ±

IL

± ±

Z

W1

R

W1

R

VL

Z

IL N

VL Z

IL

Z

Z

Y W2

IL

Fig. 14.7

804. If the p.f. of the load (phase sequence is RYB) is Fig. 14.7 is 0.5, then W1

R

± ±

Z

IL VL N IL

Z

Z

Y

B

W2

VL ± ±

IL

Fig. 14.7

A. B. C. D.

W2 will give total power W1 will give total power both W1 and W2 will read equal W2 will give negative reading

805. If the p.f. of the load (phase sequence is RYB) is Fig. 14.7 is 0.4, then W1

R

A. B. C. same D.

total power drawn will change total power drawn will not change power factor of the load remains none of the above

807. In two wattmeter method, the algebraic sum of the readings of two wattmeters will indicate true power only if A. the load is balanced B. phase sequence remains unchanged C. there is no source unbalance D. neutral wire available does not carry any current 808. Three-wattmeter method is not used to measure power in a 3-phase circuit because A. it is complicated B. generally neutral is not available or delta load cannot be opened C. it requires three wattmeters D. none of the above 809. Three resistors having the same resistances are connected in star and across 480 V 3-phase lines. To what value should the line voltage be changed to obtain the same line currents with the resistors deltaconnected? A. 230 V C. 160 V B. 133 V D. 240 V 810. In the circuit shown in Fig. 14.8, the wattmeter reads 1000 W. The total reactive power drawn by the balanced 3-phase load is

± ±

IL Z

VL IL

± ±

Fig. 14.7

W1 will give more reading than W2 both W1 and W2 will give equal and positive reading W2 will give more reading than W1 none of the above

C. D.

W2

VL ± ±

IL

Y

B

B

A. B.

Z

N

VL

W R

N

± ±

IL

N

IL Z

Z

W2

VL ± ±

B

Z

Z

Y

B

Z

IR

IY

Y

Fig. 14.7

A. B. C. D.

W2 will give negative reading both W1 and W2 will give negative reading W1 will give negative reading both W1 and W2 will give positive reading

IB Fig. 14.8

A.

1000 VAR

C.

1732 VAR

B. above

2000 VAR

D.

none of the

811. The most difficult unbalanced 3-phase load to deal with is A. 4-wire star connected unbalanced load B. unbalanced -connected load C. unbalanced 3-wire, Y-connected load D. none of the above 812. In a balanced three-phase system, the line to line voltages are displaced from each other by ____. A. 0° C. 90° B. 30° D. 120° 813. When phase sequence of the three-phase system is reversed ____. A. Phase currents change in angle not in magnitude B. Phase currents are changed C. Total Power consumed is changed D. Phase power are changed 814. A three-phase load is balanced if all the three phases have the same ____. A. Impedance B. Impedance & power factor C. Power factor D. Power 815. In balanced star (wye) connected system, the line voltage is A. 0.707 times the phase voltage B. 1.414 times the phase voltage C. phasor sum of the two phase voltage D. phasor difference of the two phase voltage 816. The phase sequence of a three-phase system is BCA. The other possible phase sequence can be ____. A. CBA C. ACB B. CAB D. none of these 817. Find the line voltage Vab is 𝑉𝑏𝑛 = 265.6∠37° V and the sequence is BCA. A. 460∠ − 203° V C. 460∠ − 83° V B. 𝟒𝟔𝟎∠ − 𝟏𝟕𝟑° V D. 460∠ − 53° V 818. Line B of a 230 V ungrounded-wye system touches the ground. What is the voltage between line A and ground? A. 230 V C. 0 B. 115 V D. 132.79 V 819. A system consists of three equal resistors connected in wye and is fed from a balanced three-phase supply. How much power is reduced if one of the resistors is disconnected? A. 33% C. 25% B. 50% D. 0% 820. Three identical wye-connected resistances consume 1,000 watts. If the resistances are connected in delta

across the same supply, the power consumed will be ____. A. 3,000 W C. 1,000 W B. 6,000 W D. 333 W 821. A balanced delta connected load draws 10 A of line current and 3 kW at 220 V. The reactance of each phase of the load is ____. A. 38.1 Ω C. 23.5 Ω B. 30 Ω D. 22 Ω 822. A 50-HP, three-phase induction motor with full load efficiency of 85% and power factor of 0.80 is connected to a three phase, 480 V system. The equivalent star connected impedance that can replace this motor is ____ A. 7.3∠ − 36.87° Ω C. 4.2∠ − 36.87° Ω B. 7.3∠36.87° Ω D. 𝟒. 𝟐∠𝟑𝟔. 𝟖𝟕° 𝛀 823. Three equal impedances of (20 + j20) ohms re connected in delta to 240 V, three-phase, 60 Hz line. Determine the capacitance of an ideal condenser in wye so that the overall power factor is 0.8 lagging. A. 16.58 μF C. 38.53 μF B. 49.74 μF D. 83.74 μF 824. Find the average power absorbed by a balance three phase load in an ACB circuit in which one line voltage is 𝑉𝑎𝑐 = 480∠30° V and one line current to the load is 𝐼𝑏 = 2.1∠80° A. A. 1337 W C. 1719 W B. 1122 W D. 1122 W 825. A balanced delta connected load having impedance per phase of 20∠30.87° ohms is supplied from a balanced 3-phase, 240 V source. Determine the total real power. A. 6824 W C. 7416 W B. 6912 W D. 6740 W 826. A balanced three-phase load draws 20 kW at 0.447 pf lagging from a 230 V, 60 Hz three phase transmission line. Find the readings of the two wattmeters properly connected to measure power. A. 18.45 kW, 1.55 kW C. 21.55 kW, -1.55 kW B. 14.25 kW, 5.75 kW D. 25.75 kW, -5.75 kW 827. A 25 HP induction motor is operating at rated load from a three phase 450 V, 60 Hz system. The efficiency and power factor of the motor are 87% and 90%, respectively. The apparent power in kVA drawn by the motor is ____. A. 23.82 C. 21.44 B. 27.78 D. 19.30 828. A balanced star connected load is supplied from a symmetrical three phase, 400 volts ABC system. The current in each phase is 30 amperes and lags 30° behind the line voltage. What is the total power? A. 18,000 W C. 20,785 W B. 10,393 W D. 31.177 W

B. 829. A balanced delta load with impedances of 15 – j9 ohms is connected to a three phase source by three wires each of which has 2 + j5 ohms impedance. The load phase voltage is 120 V. Find the line voltages of the source. A. 69 V C. 259 V B. 208 V D. 87 V 830. Two-wattmeter method is applied to a three-phase motor running at full load. The two wattmeters indicate 85.5 kW and 34.7 kW, respectively. What is the operating power factor of the motor? A. 87.45% C. 89.49% B. 80.69% D. 94.76% 831. A 100 KVA balanced three phase load operates at 0.65 power factor lagging at 450 V. If power is measured by two wattmeters, what will be the reading of each wattmeter? A. 20,000 W & 45,000 W C. 10,563 W & 54,437 W B. 25,000 W & 40,000 W D. 65,000 W & 0 W 832. The two wattmeter method is applied to a three phase, three-wire, 100 V, ABC system with the meters in lines B and C, WB = 836 watts and WC = 224 watts. What is the impedance of the balanced delta-connected load? A. 10∠45° Ω C. 𝟐𝟎∠ − 𝟒𝟓° 𝛀 B. 10∠ − 45° Ω D. 20∠45° Ω 833. Two wattmeters are connected are for the two wattmeter method with current coils in lines A and B of a 208 V, ABC circuit that has a balanced delta load. If the meter readings arte 6 kW and -3 kW respectively, find the load impedance per phase. A. 18.8∠ − 35.2° Ω/phase C. 22.3∠ − 36.2° Ω/phase B. 𝟖. 𝟏𝟖∠𝟕𝟗. 𝟏° 𝛀/𝐩𝐡𝐚𝐬𝐞 D. 32.2∠36.2° Ω/ phase 834. Three equal impedances, each represented by a series R-L circuit are connected to a three phase source. A total power of 7630 watts is measured by the two-wattmeter method. If one wattmeter gives zero deflection, determine the values of R and XL for a line voltage of 230 V. A. 3.2, 10 Ω C. 3.2, 9 Ω B. 5.2, 10 Ω D. 5.2, 9 Ω 835. Three equal impedances of (25 + j30) Ω are connected in wye to 240 V, 60 Hz, three-phase source. Determine the value of the capacitor to be connected in parallel with the load so that the total current drawn by the load is 3 amperes. A. 90 μF C. 70 μF B. 80 μF D. 60 μF 836. A delta-connected load draws 17.28 kW from 240-V, balanced three-phase supply. What is the resistance of the load if the reactance is equal to 5 ohms? A. 5 Ω C. 10 Ω

7.5 Ω

D.

2.5 Ω

837. Three identical impedances of 15∠60° ohms are connected in star to a three-phase, three-wire, 240 V system. The lines between the supply and the load have an impedance 2 + j1 ohms. Find the magnitude of the line voltage at the load. A. 123 V C. 416 V B. 240 V D. 213 V 838. A delta connected load having an impedance of (300 + j210) per phase is supplied from 480 V, threephase supply through a line having an impedance of (4 + j8) per wire. What is the total power supplied to the load? A. 1418 W C. 454 W B. 473 W D. 1363 W 839. A certain load takes 300 kW at 400 V. A three-phase capacitor bank rated 15 kVA per phase is connected in parallel with the load to raise the power factor of the load to 90% lagging. What is the power factor of the load before correction? A. 99% C. 95% B. 92% D. 88% 840. A factory load draws 100 kW at 75% lagging power factor from a 480 V source. To increase the power factor to 90% lagging, a synchronous motor operating at 80% leading power factor is connected to the load. What is the rating of the motor if it has an efficiency of 80%? A. 54 HP C. 33 HP B. 43 HP D. 35 HP 841. A three-phase, wye-connected induction motor is connected to a 480 V, three-phase supply. It draws a current of 15 amperes at 80% power factor. A delta connected reactance is connected in parallel with the motor and the combination draws 15 amperes. What is the value of the element? A. 57.4 μF C. 28.7 μF B. 122.5 μF D. 245.0 μF 842. A three-phase balanced load is connected across 220 V, three-phase, ACB source. A wattmeter with its current coil in line A and voltage coil across liens A and B reads 800 W. The potential coil is then connected across liens A and C with the current coil in the same line. What is the power factor of the load if the meter reads -800 W? A. 0.5 lagging C. 0.87 lagging B. 0.5 leading D. 0.87 leading 843. In two-wattmeter method, the readings of the wattmeter will be identical when _____. A. load in one of the two phases is zero B. C. D.

power factor is unity power factor is 0.5 neutral is earthed

844. A wye-connected, balanced three-phase load draws 75 A from 230 V, 60 Hz source. To measure the total power, two wattmeters are connected in lines A and C and reads 8,625 W and 17,250 W, respectively. Determine the impedance of the balanced load. A. 3.07∠30° Ω C. 1.77∠30° Ω B. 𝟑. 𝟕𝟕∠ − 𝟑𝟎° 𝛀 D. 1.77∠ − 30° Ω 845. Two wattmeters are used to measure the power drawn by a balanced three-phase load from a 440 V, three-phase source. The wattmeters are connected in lines A and B and reads 10 kW and -2.5 kW. When a capacitor in parallel with the load and the wattmeters reconnected in lines B and C, the wattmeter in line B reads 7.5 kW. What is the power factor of the combined load? A. 33% C. 28% B. 50% D. 72% 846. The ratio of the readings of wattmeters connected to measure the power delivered to an inductive load is 0.75. If the load draws 75 kVA from 440-V supply, determine the impedance per phase of the deltaconnected load? A. 𝟕. 𝟕𝟒∠𝟏𝟑. 𝟗° 𝛀 C. 2.58∠41.41° Ω B. 7.74∠ − 13.9° Ω 41.41° Ω

D.

2.58∠ −

847. A balanced three-phase, three-wire, 480 V supply has two loads. The first load is delta connected and takes 30 kW at 80% lagging power factor. The second load is delta connected and uses 24 kVA at 90% leading power factor. Find the readings of the two wattmeters connected in lines A and C. A. 28,940 & 22,660 W C. 30,000 & 21,600 W B. 20,400 & 31,200 W D. 32,680 & 18,920 W H. CORRECTION (3-PHASE)

POWER FACTOR

848. EE Board Exam April 1989, October 1989 A three-phase, 60 Hz, 2200 volts induction motor develops 500 HP, 0.8 lagging pf and efficiency of 94%. The power factor is raised to 0.90 lagging by connecting a bank of condensers in delta across the lines. If each of the capacitance unit is built up of four similar 550 V condensers, calculate the required capacitance of each condenser. A.

77.04 μF

C.

76.12 μF

B.

75.42 μF

D.

72.30 μF

849. EE Board Exam October 1987, October 1982 Installed in one of the customer CEPALCO are two single phase transformers each rated 75 kVA are connected V or open delta to serve a 3-phase load of 120 kW at 0.8 p.f. lagging. To prevent the overloading of the transformers, determine the size of the capacitor in kVAR.

A.

40

C.

39

B.

41

D.

42

850. EE Board Exam October 1983 Three single-phase transformers each rated 75 kVA are banked in delta and supplying a three-phase load drawing 160 kVA at 0.8 lagging power factor. If one transformer is removed for repairs, solve for the minimum amount in kVAR of a capacitor needed to prevent overloading of the remaining units. A.

70.32

C.

72.46

B.

73.64

D.

73.28

851. EE Board Exam October 1982 Two single-phase transformers each rated 75 kVA are connected in V or open delta to serve a 3-phase load of 120 W at 0.8 power factor lagging. Determine the size in kVAR of the capacitor needed to prevent overloading of the transformers. A.

40.25

C.

45.24

B.

41.28

D.

43.50

852. EE Board Exam October 1982 A 150 kVA transformer bank will serve a load expected to draw 135 kW at 0.80 lagging power factor. Solve for the size of the capacitor bank needed to be added in order to prevent overloading of the transformer bank. A.

32.506 kVAR

C.

40.391 kVAR

B.

35.866 kVAR

D.

28.266 kVAR

853. EE Board Exam October 1981 A 3-phase generator has the following 3-phase loads: an inductive load drawing 400 kVA at 0.60 pf power factor and a resistive load drawing 80 kVA at 1.00 power factor. Solve for the size in kVAR of the capacitor bank needed to improve the power factor of the combined loads to 0.85 lagging. A.

120.58 kVAR

C.

124.54 kVAR

B.

121.68 kVAR

D.

122.82 kVAR

854. EE Board Exam April 1986 A short, 3-phase, 3-wire transmission line has a receiving end voltage of 4,160 V phase to neutral and serving a balanced 3-phase load of 998.400 volt-amperes at 0.82 pf lagging. At the receiving end the voltage is 4600 V., phase to neutral and the pf is 0.77 lagging. Solve for the size in kVAR of a capacitor needed to improve the receiving end pf to 0.9 lagging maintaining 4160 V. A.

181

C.

172

B.

175

D.

178

855. REE Board Exam October 1996 A 132 kV line, three-phase system delivers 70.7 MVA of a balanced delta load of power factor 70.7%. Determine the reactance necessary in order to attain unity power factor. A. 1,092 Ω C. 1,142 Ω B. 965 Ω D. 1,045 Ω 856. EE Board Exam October 1980 A balanced 500 kVA, 3-phase, 440 volt, 60 Hz, inductive load operates at a pf of 75%. Determine the total capacitive kVAR required improving the pf to 95%. A.

207.46

C.

210.75

B.

176.42

D.

192.21

857. EE Board Exam October 1984 A balanced 3-phase load draws 150 A phase current at 7.5 kV phase to neutral, 0.891 power factor lagging. It is desired to raise the power factor to 0.96 leading. Solve for the amount of capacitor kVAR needed to achieve such pf. A.

2273 kVAR

C.

2509 kVAR

B.

2409 kVAR

D.

2365 kVAR

858. EE Board Exam April 1981 A 3-phase, 3-wire, short transmission line has a resistance of 3 ohms and a reactance of 8 ohms per wire. At the receiving end, a balanced 3-phase load draws a line current of 60 A, at 13,500 volts line to line, 0.90 power factor lagging. Assuming the receiving end voltage is maintained at 13,500 V, solve for the size in kVAR of capacitors needed to raise the power factor at the receiving end to 0.95 leading. A.

1043.5

C.

1026.5

B.

1154.2

D.

1232.2

859. EE Board Exam April 1981 A three-phase balanced load draws a line current of 80 A at 0.90 lagging power factor. Solve for the minimum size in kVAR of the capacitor bank needed to raise the power factor to 0.96 leading, if the line to line voltage is 13,200 volts. A.

1310.15

C.

1247.54

B.

1338.25

D.

1430.12

860. EE Board Exam October 1990

Two Y-connected, 50° rise induction motors are fed by a 4160 V, line to line, 3-phase 60 Hz motorcontrol center 20 feet away. Motor 1 drives a 600hp compressor. The efficiency of this motor is 90% and its power factor is 0.5. Instruments of motor 2 indicate 1730 kW, 277 amperes. Determine the capacity in microfarads per phase of a wyeconnected bank that is required to correct the power factor of the load to 0.966 lagging. A.

172.4 μF

C.

167.2 μF

B.

193.8 μF

D.

182.1 μF

861. EE Board Exam April 1993 A star-connected 400 HP (metric), 2000 V, 50 c/s motor works at a power factor of 0.7 lagging. A bank of mesh-connected condensers is used to raise the power factor to 0.93 lagging. Calculate the capacitance of each unit required if each is rated 500 V, 50 c/s. The motor efficiency is 85%. A.

194 μF

C.

302 μF

B.

225 μF

D.

233 μF

862. A delta connected induction motor takes 20 kW at 0.8 pf from a 500 V 60 Hz mains. Three delta connected capacitors are used to raise the pf to 0.95. What is the capacitance of each capacitor in F? A. 22.3 F C. 29.8 F B. 28.7 F D. 38.9 F 863. A three-phase induction motor delivers 150 HP while operating at 80% efficiency and a power factor of 0.8 lagging from 480 V lines. A wye connected power factor correction capacitor is to be installed to improve the overall power factor to 0.9 lagging. Determine the capacitance required per phase. A. 428 μF C. 1283 μF B. 142.6 μF D. 3850 μF G. UNBALANCED POLYPHASE SYSTEMS 864. EE Board Exam April 1982 Given a balanced 3-wire, three-phase system serving the following loads: 𝑉𝑎𝑏 = 200∠0° 𝑉

𝑍𝑎𝑏 = 10∠53.13° Ω

𝑉𝑏𝑐 = 200∠240° 𝑉

𝑍𝑏𝑐 = 10∠0° Ω

𝑉𝑐𝑎 = 200∠120° 𝑉

𝑍𝑐𝑎 = 10∠30° Ω

Determine the current on line b A.

20.34 A

C.

24.36 A

B.

22.04 A

D.

21.57 A

865. EE Board Exam April 1982 Given the following line voltages and two load impedances: 𝑉𝑎𝑏 = 117∠0° 𝑉

𝑍𝑎𝑏 = 5 + 𝑗12 Ω

𝑉𝑏𝑐 = 117∠240° 𝑉

𝑍𝑏𝑐 = 13 + 𝑗0 Ω

𝑉𝑐𝑎 = 117∠120° 𝑉 Solve for the current in line c. A.

17.41 A

C.

16.62 A

B.

17.95 A

D.

18.46 A

866. EE Board Exam April 1988 Three unequal single-phase loads so connected across the lines of a balanced, 3-phase, 230 volts circuit. The first takes 106 A at 0.78 pf lagging and is connected across lines 1 & 2. The second takes 142 A, at 0.82 pf lagging and is connected across lines 2 & 3. And the third takes 28.4 kW at 0.77 pf lagging and is connected across lines 3 & 1. Find the three line currents.

rated 8 hp, 230 V, 0.70 pf, 0.90 efficiency, which is connected across lines a and b. Load B draws 5 kW at 1.0 pf and is connected across lines b and c. Assume a sequence of a-b-c, solve for the current on line b. A.

42.19 A

C.

41.08 A

B.

27.74 A

D.

34.46 A

870. EE Board Exam April 1980 A factory is supplied by a three-phase, 3-wire system with the following characteristics: 𝑉𝑎𝑏 = 230∠0° 𝑉

𝐼𝑎 = 110∠ − 36.87° 𝐴

𝑉𝑏𝑐 = 230∠240° 𝑉

𝐼𝑐 = 125∠53.13° 𝐴

Find the line current Ib.

A.

254.40 A, 211.38 A, 252 A

A.

145.3 A

C.

184.6 A

B.

231.26 A, 215.20 A, 268 A

B.

163.3 A

D.

166.5 A

C.

254.40 A, 215.20 A, 252 A

D.

231.26 A, 211.38 A, 268 A

867. EE Board Exam October 1992 A 120-V per phase, three-phase Y-connected source delivers power to the following deltaconnected load:

871. EE Board Exam April 1988 Three unequal single-phase loads so connected across the lines of a balanced, 3-phase, 230 volts circuit. The first takes 106 A at 0.78 pf lagging and is connected across lines 1 & 2. The second takes 142 A at 0.82 pf lagging and is connected across 2 & 3. And the third takes 28.4 kW at 0.77 pf lagging. Determine total apparent power.

𝑃ℎ𝑎𝑠𝑒 1 = 40∠0°

A.

94 kVA

C.

78 kVA

𝑃ℎ𝑎𝑠𝑒 2 = 20∠ − 60°

B.

83 kVA

D.

101 kVA

𝑃ℎ𝑎𝑠𝑒 3 = 15∠45° Solve for the three line currents. A.

12.45 A, 9 A, 22.45 A

B.

13.49 A, 9 A, 22.45 A

C.

13.49 A, 10 A. 20.22 A

D.

12.45 A, 10 A, 20.22 A

868. EE Board Exam October 1985 Given: 𝑉𝑎𝑏 = 240∠0° 𝑉

𝑍𝑎𝑏 = 6 + 𝑗8 Ω

𝑉𝑏𝑐 = 240∠240° 𝑉

𝑍𝑏𝑐 = 5 + 𝑗8.66 Ω

𝑉𝑐𝑎 = 240∠120° 𝑉

𝑍𝑐𝑎 = 10 + 𝑗0 Ω

Solve for the three line currents Ia, Ib and Ic. A. Ia = 45 A, Ib = 43 A, Ic = 20 A B. Ia = 48 A, Ib = 42 A, Ic = 24 A C. Ia = 45 A, Ib = 42 A, Ic = 20 A D. Ia = 48 A, Ib = 43 A, Ic = 24 A 869. EE Board Exam April 1985 A three phase 230-V circuit serves two singlephase loads, A and B. Load A is an induction motor

872. REE Board Exam October 1996 The following information is given for a deltaconnected load of three numerically equal impedances that differ in power factor. Line voltage = 120 volts. 𝑍𝑎𝑏 = 15∠30° Ω, 𝑍𝑏𝑐 = 15∠0° Ω and 𝑍𝑐𝑎 = 15∠ − 30° Ω. Phase sequence of voltages is a-b-c. Using the phase sequence as a guide, calculate the total power drawn by the load. A.

2,624 W

C.

2,564 W

B.

2,472 W

D.

2,731 W

873. EE Board Exam April 1993 In AC circuit, find the total power in kW in an unbalanced three-phase circuit loaded as follows: Phase I = 120 V, 100 A, unity pf. Phase II = 100 V, 230 A, 80% pf and phase III = 110 V, 85 A, 77% pf. A.

37.6 kW

C.

32.8 kW

B.

35.3 kW

D.

38.2 kW

874. EE Board Exam April 1983 Two single-phase transformers are connected in V (open delta) and serving a delta connected

impedance load. Each impedance is equal to 16∠36.87° Ω. If the transformer voltages impressed on the impedances are 𝑉𝑎𝑏 = 240∠0° 𝑉, 𝑉𝑏𝑐 = 240∠240° 𝑉, 𝑉𝑐𝑎 = 240∠120° 𝑉. Solve for the total kVA drawn by the load.

Solve for the real power in kW drawn by the commercial building.

A.

6.23

C.

10.8

A.

402.2

C.

419.5

B.

8.31

D.

11.3

B.

404.5

D.

421.5

875. EE Board Exam October 1980, October 1982 Three impedances Zan = 20 + j0, Zbn = 16 + j12, Zcn = 5 – j15 ohms, are connected in wye across a 230 V (line to line), 3-phase, 4-wire source. The phase sequence is a-b-c, counterclockwise. Determine the current passing thru the neutral.

𝑉𝑎𝑏 = 2,400∠0° 𝑉

𝐼𝑎 = 85∠330° 𝐴

𝑉𝑏𝑐 = 2,400∠240° 𝑉

𝐼𝑐 = 100∠80° 𝐴

880. EE Board Exam October 1981 A 3-phase, 3-wire load draws the following line currents: 𝐼𝑎 = 60∠330° 𝐴, 𝐼𝑏 = 78.4∠214° 𝐴 and 𝐼𝑐 = 75∠80° 𝐴. If the voltages impressed on the load are balanced 3-phase, having a magnitude of 4140 volts line to line, solve for the total power in kW.

A.

7.54 A

C.

8.81 A

A.

556.16

C.

536.54

B.

9.12 A

D.

8.02 A

B.

506.85

D.

520.18

876. EE April 1981 A wye-connected transformer with neutral connection has balanced voltages of 265 V between lines and neutral. The transformer is serving two single phase motors. Motor A (rated 4 hp, 0.90 efficiency, 0.80 power factor lagging) is connected across line a and neutral. Motor B (rated 3 hp, 0.85 efficiency, 0.85 power factor lagging) is connected across line b and neutral. Solve for the neutral current, using Van as reference vector. A.

20.42 A

C.

22.45 A

B.

25.37 A

D.

23.14 A

877. REE Board Exam October 1998 The loads of a wye connected transformer are: Ia = 10 cis (-30°); Ib = 12 cis 215°; Ic = 15 cis 82°. What is the neutral current? A. 1.04 cis 72.8° C. 0.92 cis 62.5° B.

2.21 cis (-30°)

D.

3.11 cis 72.6°

881. EE Board Exam October 1983 Given the following load impedances in delta and the impressed voltages as follows: 𝑉𝑎𝑏 = 220∠0° 𝑉

𝑍𝑎𝑏 = 8 + 𝑗6 Ω

𝑉𝑏𝑐 = 220∠240° 𝑉

𝑍𝑏𝑐 = 8.66 − 𝑗5 Ω

𝑉𝑐𝑎 = 220∠120° 𝑉

𝑍𝑐𝑎 = 10 + 𝑗0 Ω

What will be the reading of the two wattmeters connected to measure total power. Use line a as the common potential point. A. C.

3.869 kW, 9.031 kW 3.125 kW, 6.778 kW

B. D.

2.546 kW, 8.357 kW 4.055 kW, 9.848 kW

882. EE Board Exam October 1984 The 3-phase power supply to a factory has the following measurements:

878. EE Board Exam April 1980 A factory is supplied by a three-phase, 3-wire system with the following characteristics:

𝑉𝑎𝑏 = 240∠0° 𝑉

𝐼𝑎 = 120∠330° 𝐴

𝑉𝑏𝑐 = 240∠240° 𝑉

𝐼𝑏 = 157∠214° 𝐴

𝑉𝑐𝑎 = 240∠120° 𝑉

𝐼𝑐 = 150∠80° 𝐴

𝑉𝑎𝑏 = 230∠0° 𝑉

𝐼𝑎 = 110∠ − 36.87° 𝐴

Solve for the total power drawn.

𝑉𝑏𝑐 = 230∠240° 𝑉

𝐼𝑐 = 125∠53.13° 𝐴

A.

60.2 kW

C.

58.8 kW

B.

56.5 kW

D.

62.4 kW

Determine the power consumed by the load. A.

42.75 kW

C.

40.23 kW

B.

48.78 kW

D.

45.12 kW

879. EE Board Exam April 1981 The following voltages and line currents were measured to a 3-phase, 3-wire feeder serving a commercial building:

883. EE Board Exam April 1985 A three-phase 230-V circuit serves two singlephase loads, A and B. Load A is an induction motor rated 8 hp, 230 V, 0.70 pf, 0.90 efficiency, which is connected across lines a and b. Load B draws 5 kW at 1.0 pf and is connected across lines b and c.

Assume a sequence of a-b-c, solve for the total power factor of the load. A.

0.907

C.

0.864

B.

0.704

D.

0.886

884. EE Board Exam October 1987 A wound rotor motor, 7.5 HP, 230 volts, 3-phase takes a line current of 18.4 ampere, when operating at rated output at an efficiency of 88%. Calculate the indication on the wattmeter when this is inserted to measure power by the T-method. A.

3.179 kW

C.

3.361 kW

B.

4.401 kW

D.

4.042 kW

885. EE Board Exam October 1994 A wattmeter with its current coil in line 2 and potential coil across lines 2 and 3 is connected to a balanced 3-phase system. The only load supplied is a single phase one connected to lines 1 and 2. This load is known to be inductive. If the wattmeter reads zero watts, determine the power factor of the singlephase load. A.

0.707

C.

0.800

B.

0.866

D.

0.900

886. EE Board Exam April 1984 A balanced 3-phase load draws 75 amperes line current at 230 volts line to line and 0.848 lagging power factor. If the two-wattmeter is used, solve for the readings of the two wattmeters. A. C.

15.32 kW, 10.02 kW 16.42 kW, 8.92 kW

B. D.

17.86 kW, 7.48 kW 17.24 kW, 8.10 kW

887. EE Board Exam October 1980 Three equal impedances, each having a resistance of 8 ohms and an inductive reactance of 7 ohms are connected in delta to lines a, b and c of a 240 V, 3phase, 3-wire line, phase sequence a-b-c. What is the reading of a single-phase wattmeter connected with its current coil in line a and the potential coil across lines b and c? A.

6,180 W

C.

6,561 W

B.

6,324 W

D.

6,004 W

888. EE Board Exam October 1992 A 3-phase feeder carries two lagging balanced loads. The power observed by each is measured by two wattmeter method, giving the following readings:

First Load:

W1 = 160 kW

W2 = 96 kW

Second Load:

W1 = 90 kW

W2 = 48 kW

What is the combined kVA load on the feeder? A.

434.68

C.

504.35

B.

462.35

D.

420.12

889. EE Board Exam October 1992 National Power Corporation used two wattmeters to measure 3-phase power of a balanced Y-connected lagging power factor motor loads. Each wattmeter indicates 15.4 kW. The voltage coils are connected across lines 2 and 3, and across lines 1 and 3, respectively. The line to line voltages are 230 volts with V12 leading V23 and the line currents are each 120 A. Calculate the total power supplied. A.

37.44 kW

C.

39.67 kW

B.

30.72 kW

D.

34.88 kW

890. EE Board Exam April 1980 A factory is supplied by a three-phase, 3-wire system with the following characteristics: 𝑉𝑎𝑏 = 230∠0° 𝑉 36.87° 𝐴

𝐼𝑎 = 110∠ −

𝑉𝑏𝑐 = 230∠240° 𝑉

𝐼𝑐 = 125∠53.13° 𝐴

A.

0.934 lagging

C.

0.892 lagging

B.

0.908 lagging

D.

0.866 lagging

891. EE Board Exam October 1981 A 3-phase, 3-wire load draws the following line currents: 𝐼𝑎 = 60∠330° 𝐴, 𝐼𝑏 = 78.4∠214° 𝐴 and 𝐼𝑐 = 75∠80° 𝐴. If the voltages impressed on the load are balanced 3-phase, having a magnitude of 4140 volts line to line, solve for the power factor of the load. A.

0.976

C.

0.982

B.

0.999

D.

0.906

892. EE Board Exam April 1995 Three unequal single-phase induction motor loads are connected across the lines and neutral conductor of a balanced, 3-phase, 350 volts circuit. The line to neutral voltages is each 202 volts. The first load takes 20 kW at 0.82 power factor, the second takes 28 kW at 0.75 power factor, and the third takes 36 kW at 0.80 power factor. What is the current in the neutral conductor? A.

105.5 amps

C.

125.4 amps

B.

86.6 amps

D.

none of these

893. For an unbalanced load which connection is suitable A. 3 wire open delta B. 4 wire star connection C. 3 wire delta connection D. 3 wire star connection 894. What is the minimum number of wattmeters required for measuring power of a three phase balanced load? A. two C. one B. four D. three 895. The power is to be measured for a balanced delta connected load whose terminals cannot be opened. How many wattmeters do you need? A. four C. two B. one D. three 896. What is the minimum number of wattmeters required to measure unbalanced power for a three-phase system? A. two C. three B. four D. one 897. In two wattmeter method, the readings of the wattmeter will be identical when A. load in one of the phases is zero B. power factor is unity C. power factor is 0.5 D. neutral is earthed 898. Two wattmeters can be used to measure 3-phase for a A. balanced and unbalanced load B. unbalanced load only C. balanced load only D. unity power factor only 899. In 2 wattmeter method, the reading of one of the wattmeter will be zero when A. power factor is unity B. power factor is 0.5 C. load in one of the phases is zero D. a neutral wire is not provided 900. For a 3 phase unbalanced load A. the power factor of each phase will be in proportional to the load B. the power factor of each phase will be the same C. the power factor of at least one of the phase must be leading D. the power factor of each phase may be different 901. A wattmeter is installed in a balanced 3-phase system. The wattmeter will measure

A. B.

total power real power

C. D.

active power reactive power

902. A three-phase, three-wire, 240 V, CBA system supplies power a wye-connected load with impedances of 𝑍𝑎 = 𝑍𝑏 = 25∠90° Ω, 𝑍𝑐 = 20∠0° Ω. Find the total power. A. 1,553 W C. 1,883 W B. 2,589 W D. 2,104 W 903. A 100 V, balanced three-phase source has two single-phase loads. The first load has an impedance of (5 + jX) ohms and connected across lines A and B. The second load is connected across B and C and has an impedance of (R – j2) ohms. Determine the values of R and X, if the current in line B is 25.93∠ − 102.37° A and the ratio of X to R is 1.5. A. 2 Ω, 3 Ω C. 4 Ω, 6 Ω B. 3 Ω, 4.5 Ω D. 5 Ω, 7.5 Ω 904. Three – single phase loads are connected between lines of a 280 V, balanced three phase source. The currents measured in lines B and C are: 𝐼𝑏 = 85.22∠ − 72.5° A, 𝐼𝑐 = 60.71∠170° A. What is the negative sequence component of the currents? A. 39.21∠105.2° A C. 37.64∠ − 104.5° A B. 𝟑𝟑. 𝟗𝟑∠𝟏𝟔𝟏. 𝟔° A D. 41.82∠72.8° A 905. Two of the three unbalanced currents are given for an unbalanced, three-phase system. Find the positive sequence of phase B current of the neutral current is 32∠39.2° A. A. 32∠39.2° A C. 106.23∠61.5° B. 181∠47.1° A D. 𝟔𝟎. 𝟑𝟑∠ − 𝟒𝟏. 𝟕° A 906. The phase b voltage and the phase b current of a balanced 3-phase system are: V = 220 sin (t + 210°) and I = 10 sin (t – 180°). What is the power of the system? A. 3300 W C. 1905 W B. 5716 W D. 3810 W 907. Two voltage generators are in series. The voltage being generated are Vab = 50 sin(t - 30°) and Vbc = 100 sin(t + 60°). What is the output voltage Vac? A. 111.83 cis 33.5° C. 145.5 cis 50.1° B.

50 cis 30°

D.

150 cis 30°

TWO PORT NETWORKS 908. As the poles of a network shift away from the axis, the response A. remain constant C. becomes more oscillating B. becomes less oscillating D. none of these

R Y B

909. The response of a network is decided by the location of A. Its zeros C. both zeros & poles

B. Its poles nor poles

D.

neither

zeros

910. The pole-zero configuration of a network function is shown. The magnitude of the transfer function will A. Decrease with frequency B. increase with frequency C. Initially increase and then decreases with frequency D. Be independent of frequency 911. Given I1 = 2V1 + V2 and I2 = V1 + V2 the Zparameters are given by A. 2, 1, 1, 1 C. 1, 1, 1, 2 B. 1, -1, -1, 2 D. 2, -1, 1, 1 912. The short – circuit admittance matrix of a two-port network is as shown The two-port network is A. Non reciprocal & passive B. Non-reciprocal & active C. Reciprocal & passive D. reciprocal & active 913. If the two port network is reciprocal, then A. Z12 / Y12 = Z122 – Z11 Z12 B. Z12 = 1/Y22 C. h12 = -h21 D. AD-BC = 0 914. Two networks are cascaded through an ideal buffer. If tr1 & tr2 are the rise times of two networks, then the over-all rise time of the two networks together will be A. √ tr1 tr2 C. tr1 + tr2 B. √ (tr12 +tr22) D. (tr1 + tr2 )/ 2 915. Which one of the following combinations of open circuit voltage and Thevenin’s equivalent resistance represents the Thevenin’s equivalent of the circuit shown in the given figure?

A. B.

1 V, 10 Ω C. 1 V, 1 kΩ D.

D.

Symmetrical Components

1 mV, 1 kΩ 1 mV, 10 Ω

916. REE Board Exam October 1998 If the loads of a wye-connected transformer are: Ia = 10 cis (-30°) Ib = 12 cis 215° Ic = 15 cis 82° What is the phase b positive sequence component? A. 13.4 cis (-32.2°) C. 12.27 cis 208.4°

B. 10.2 cis 240° 31.6°)

D.

12.27

cis

(-

917. REE Board Exam March 1998, September 2001 The three unbalanced currents are: Ia = 10 cis (-30°) Ib = 0 Ic = 10 cis 150° Find the negative sequence current of phase a. A. 8.66 cis 30° C. -5.77 B. 5.77 cis (-60°) D. 5.77 918. EE Board Exam October 1984 Given the following currents: Ia = 60 + j0 A Ib = -36 – j48 A Ic = -48 + j36 A Solve for the negative sequence component Ia. A. 8.641 – j1.543 C. 9.751 – j1.464 B. 9.436 + j1.346 D. 8.354 + j1.034 919. REE Board Exam October 1998 The three unbalanced currents are: Ia = 10 cis (-30°) Ib = 0 Ic = 10 cis 150° Find the zero sequence current. A. 3.33 cis 30° C. 5.77 B. 0 D. 3.33 920. EE Board Exam October 1984 Given the following currents: Ia = 60 + j0 A Ib = -36 – j48 A Ic = -48 + j36 A Solve for the zero component of Ia. A. 10 + j4 C. -8 – j4 B. 8 – j6 D. 12 – j6 921. REE Board Exam October 1997 The sequence currents of phase a current are as follows: Zero sequence current = 14.13∠17.34° Positive sequence current = 2.98∠10.06 Negative sequence current = 708.26∠ − 31° Determine the phase a current. A. 𝟕𝟐𝟎∠ − 𝟑𝟎° C. 710∠88° B. 730∠ − 15.2° D. 695∠15.2° 922. REE Board Exam October 1998 The sequence components of phase a current are: Zero sequence current = 0.47 + j1.49 Positive sequence current = 18.4 cis (-31.6°) Negative sequence current = 3.23 cis 168.2° Determine the phase b current. A. 18 cis 215° C. 19 cis 220° B. 15 cis 240° D. 20 cis 225° 923. REE Board Exam March 1998 The sequence components of phase a current are: Zero sequence current = 0.47 + j1.49 Positive sequence current = 18.4 cis (-31.6°) Negative sequence current = 3.23 cis 168.2°

Determine the phase c current. A. 17.5 cis 91° C. B. 18 cis 215° D.

22.5 cis 82° 15 cis 100°

924. EE Board Exam April 1992 Determine the symmetrical components of the line current in line ‘a’ if one of the in-phase impedance of its delta connected load connected across lines ‘ca’ is removed. The delta load with impedance of 10∠0° ohms per phase is supplied from a 220 volts, 60 cycle, 3-phase source. Assume a phase sequence of a-b-c. A. Ia1 = 11 A, Ia2 = 11 A, Ia0 = 0 A B. Ia1 = 7.33 A, Ia2 = 7.33 A, Ia0 = 7.33 A C. Ia1 = 22 A, Ia2 = 22 A, Ia0 = 22 A D. Ia1 = 25.4 A, Ia2 = 12.7 A, Ia0 = 0 A 925. EE Board Exam April 1991 A star-connected balanced load takes 75 A from a balanced 3-phase, 4-wire supply. If the two supply lines of the fuses are removed determine the symmetrical components of the lines after the fuses are removed. A. I1 = 25 A, I2 = 25 A, I3 = 25 A B. I1 = 25 A, I2 = 50 A, I3 = 0 A C. I1 = 75 A, I2 = 75 A, I3 = 75 A D. I1 = 75 A, I2 = 0 A, I3 = 0 A 926. REE Board Exam September 2000 If the loads of a wye-connected transformer are: Ia = 10 cis (-30°) Ib = 12 cis 215° Ic = 15 cis 82° Find the positive sequence component of phase a current. A. 13.4 cis (-32.2°) C. 12.27 cis 208.4° B. 10.2 cis 240° D. 12.27 cis (31.6°) 927. The method of symmetrical components is very useful for A. solving unbalanced polyphase circuits B. analyzing the performance of 3-phase electrical machinery C. calculating currents resulting from unbalanced faults D. all of the above 928. An unbalanced system of 3-phase voltages having RYB sequence actually consists of A. a positive-sequence component B. a negative-sequence component C. a zero-sequence component D. all of the above 929. The zero-sequence component of the unbalanced 3phase system of vectors VA, VB and VC is of their vector sum. A. one-third C. two-third B. one-half D. one-fourth

930. In the case of an unbalanced star-connected load supplied from an unbalanced 3-, 3 wire system, load currents will consists of A. positive-sequence components B. negative-sequence components C. zero-sequence components D. only A and B 931. In symmetrical components, what is the vector sum of 1 + a + a2? A. 1 C. -1 B. 0 D. infinity 932. REE Board Exam October 1997 The sequence currents of a three phase current are: Zero sequence current = 14.13 cis 17.34° Positive sequence current = 708.26 cis (-31°) Negative sequence current = 2.98 cis 10.06° Determine the phase a current. A. 720 cis (-30°) C. 710 cis 88° B. 730 cis (-15.2°) D. 695 cis 15.2° 933. REE Board Exam April 2001 The three unbalanced currents are: Ia = 10 cis (-30°) Ib = 0 Ic = 10 cis 150° Find the phase B positive sequence current. A. 8.66 A C. 5.77 A B. 5.77 cis 240° A D. 8.66 cis 120° A 934. REE Board Exam September 2002 The phase currents of a three-phase system are: Ia = 100 cis 0° Ib = 80 cis 240° Ic = 91.8 cis 130.9° Find the zero sequence current. A. 90.23 cis 3.68° A B. 270.7 cis 3.68° A C. 34.68 cis (-30.24°) A D. none of the above 935. Given three unbalanced three-phase voltages: Va = 150 + j0 V Vb = -90 – j120 V Vc = -120 + j90 V Determine Va1 A. 142.43 + j12.35 B. 135.32 – j 1.34 C. 145.62 + j13.66 D. 140.23 – j9.32 936. A. B.

1.

C. D.

Four 3 pCoul spheres are in corners of square q 1 cm on sides. Find the force in Newton?

The correct answer is: 15.5 x 10^(-10)

2.

The correct answer is: 0.999

In a cable capacitor, voltage gradient is maximum at the surface of the 9.

3.

When will an ac voltage, v = 120 sin 120*pi*t reach

The correct answer is: conductor

its first peak?

Which of the following voltmeter has the most

The correct answer is: 4.167 ms

inaccurate reading? 10. A balanced delta load with impedances of 15 - j9 The correct answer is: Low sensitive, 900 kohms

ohms is connected to a three phase source by three wires each of which has 2 + j5 ohms impedance.

4.

Electrostatic instruments are exclusively used as

The load phase voltage is 120 V. Find the line voltages at the source. The correct answer is: 259 V

The correct answer is: voltmeters

11. A three-phase motor takes 10 kVA at 0.67 pf lagging from a source of 230 volts. It is in parallel

5.

The input impedance of your test equipment should exceed the impedance of the circuit under test by what ratio?

The correct answer is: 10 to 1

6.

Part of the which produces bright spot through collection of electrons

with a balanced delta load having 16 ohms resistance and 12 ohms capacitive reactance in series in each phase. Determine the total power factor.

The correct answer is: 0.967 lagging

12. To roughly check his kWh meter an electrician hook-up a wattmeter, he switched on the load, he counted 5 rev in 18 sec, the meter constant is 3.2.

The correct answer is: Aquadag coating

The wattmeter reads 368 Watts. What is the error of the meter?

7.

An isolated sphere 10 cm in radius is charged in air to 500 Volts. How much charge is required?

The correct answer is: 8% slower 13. Two single-phase transformers are connected in V (open delta) and serving a delta connected impedance load. Each impedance is equal to 16 cis

The correct answer is: 5.563 nC

(36.87 deg) ohms. If the transformer voltages impressed on the impedances are Vab = 240 cis (0 deg) V, Vbc = 240 cis (240 deg) V, Vca = 240 cis

8.

A 3-phase, 3-wire load draws the following line

(120 deg) V. Solve for the total kVA drawn by the

currents: Ia = 60 cis (330 deg) A, Ib = 78.4 cis (214

load.

deg) A, Ic = 75 cis (80 deg) A. If the voltages impressed on the load are balanced 3-phase,

The correct answer is: 10.8 14. Three resistance are connected in series has a total

having a magnitude of 4140 volts line to line, solve

resistance of 120 ohms. If Rx = 20 ohms and Ry is

for the power factor of the load.

twice greater than Rz. Find Ry and Rz.

The correct answer is: Ry = 75 ohms& Rz = 25 ohms 15. The resistance of a coil of wire is 1 k-ohms at 20 degrees C. If the coil is immersed into oil, the resistance falls to 880 ohms. If the wire has a temperature coefficient of 0.006 at 20 degrees C, how much is the temperature of the liquid? The correct answer is: 0 degrees C 16. Which of the following ammeters is the most sensitive? The correct answer is: 0 - 1 micro-ammeter 17. A plate capacitor is made up of 501 sheet of

22. A dc motor draws 200 Amp is located at 100 ft from the supply line. The wire has a resistance of 0.01 ohm per 100 ft. What is the voltage at the motor terminals if the supply voltage is 120 Volts? The correct answer is: 116 volts 23. Find the Thevenin impedance equivalent across R2 of a linear close circuit having 10 volt supply in series with two resistors (R1= 50 ohms and R2 = 200 ohms). The correct answer is: 40 ohms 24. A 10 ohms R1, 30 ohms XL and 60 ohms XL are connected in parallel across a 220 volts 60 Hz

aluminum 25 cm x 30 cm with a dielectric of paraffin

source. What is the current in R1 in ampere?

paper 0.0015 cm thick. What is the capacitance in

The correct answer is: 22

microfarads of the condenser (K for paraffin paper is 2.3)? The correct answer is: 25 18. A three-phase balanced load is connected across 220 V, three-phase, ACB source. A wattmeter with its current coil in line A and voltage coil across lines A and B reads 800 W. The potential coil is then connected across lines A and C with the current coil

25. A load of 10 ohms was connected to a 12-volt battery. The current drawn was 1.18 amperes. What is the internal resistance of the battery? The correct answer is: 0.20 ohm 26. What is a dielectric? The correct answer is: an insulator between two metal plates in a capacitor 27. The time constant of an R-C circuit is defined as the

in the same line. What is the power factor of the

time during which capacitor charging current

load if the meter reads -800 W?

becomes ____ percent of its ____ value.

The correct answer is: 0.87 lagging

The correct answer is: 37, initial 28. The unit of electric intensity is The correct answer is: both B and C 29. For medium, electric flux density is related to

19. Two electrons in a vacuum experience a force of 2 x 10^-15 N. How far apart are the electrons?

electric density E by the equation The correct answer is: D = (permittivity of free space*relative permittivity)E

The correct answer is: 3.39 x 10^-7 m

30. Which part of the oscilloscope emits electrons? The correct answer is: Heater cathode 31. A coil has a resistance of 100 ohms at 90 degrees

20. Calculate the capacitance between two parallel

C. At 100 degrees C, its resistance is 101 ohms.

plates each of which is 100 cm^2 and 2 mm apart in

What is the temperature coefficient of the wire at 90

air.

degrees C?

The correct answer is: 0.443 uuF

The correct answer is: 0.001

21. The hot resistance of a 100 watt, 250 V incandescent lamp would be The correct answer is: 625 ohms

32. When the grid bias of the oscilloscope is varied, what is being controlled?

The correct answer is: Amplitude 33. An electric water heater has a rating of 1 kW, 230

43. Three capacitors A, B and C are charged as follows: A = 10 uF, 100 V; B = 15 uF, 150 V and C =

V. The coil used as the heating element is 10 m

25 uF, 200 V. They are connected in parallel with

long and has a resistivity of 1.724 x 10^-6 ohm-cm.

terminals of like polarity together. What is the

Determine the required diameter of the wire in mils.

voltage across the combination?

The correct answer is: 2.52 mils 34. The most efficient form of damping employed in electrical instruments is The correct answer is: eddy currents 35. When using an ohmmeter to measure the continuity of a wire, the resistance should measure The correct answer is: both A and B 36. If relative permittivity of mica is 5, its absolute

The correct answer is: 165 V 44. A current meter should have a The correct answer is: very low internal resistance 45. A capacitor is charged by a constant 10 mA current source which is turned on for 1 second. Assuming the capacitor is initially uncharged, determine the power supplied by the source if the capacitor has a value of 1 mF.

permittivity is The correct answer is: 5*(permittivity of free space)

The correct answer is: 100 mW

37. A 150 kVA transformer bank will serve a load expected to draw 135 kW at 0.80 lagging power

46. If an oscilloscope with a vertical deflection of 0.1

factor. Solve for the size of the capacitor bank

volt rms per centimeter (cm), is used in conjunction

needed to be added in order to prevent overloading

with a 10 ohm shunt resistor to measure a 25 milli-

of the transformer bank.

amp current, compute the vertical deflection?

The correct answer is: 35.866 kVAR 38. The permeability of free space The correct answer is: 4pi x 10^-7 H/m

The correct answer is: 2.5 cm

39. If admittance Y = 0.06 - j0.08 mho, then conductance G equals The correct answer is: 0.06

47. What is the most accurate of all instruments for measuring high power?

40. A certain precision 1 micro-farad capacitor has a very high resistance material used between its conducting surfaces. The capacitor is charged to 1

The correct answer is: Bolometer

volt at t = 0 and disconnected from the source. It is found that the voltage drops to 0.9 volt in 100 hour. Find the insulation resistance of the capacitor. The correct answer is: 3420 G-ohms

48. An uncharged capacitor in series with a 120 volt voltmeter of 10,000 ohms resistance is suddenly connected to a 100 V battery. One second later, the

41. In an R-C circuit across a d. c voltage source, which of the following is zero at the beginning of the

voltmeter reads 60 volt. Determine the capacitance of the capacitor.

transient? The correct answer is: capacitor voltage 42. An inductive reactance of 8 ohms is connected in

The correct answer is: 195.76 uF

parallel with a capacitive reactance of 18 ohms. This combination is then connected in series with a variable resistance. For what value of resistance will the power factor be 0.5? The correct answer is: 8.314 ohms

49. A galvanometer has a resistance of 300 ohms. What is the ohmic resistance to make it read one is to ten?

The correct answer is: 33.33

The correct answer is: watthour meter 10. The moving coil-current in a wattmeter is

50. How do you design direct current ammeter such that is could read high current values?

proportional to the _____ across the circuit. The correct answer is: Voltage 11. For a moving-coil meter movement, the full scale current deflection is

The correct answer is: Employ shunt resistor across

The correct answer is: the amount of current needed in the moving-coil to produce full-scale

1.

What is the common type of meter movement? The correct answer is: D Arsonval

2.

A certain wire 20 ft long and 100 circular mil area has a resistance of 1.6 ohms. What is its resistivity? The correct answer is: 8 ohm-CM/ft

3.

What is the rms value of a square wave with an amplitude of 10 A and frequency of 1 Hz? The correct answer is: 10 A

4.

The meter that is suitable for only direct current measurement is The correct answer is: permanent magnet type

5.

deflection of a pointer of the meter 12. A wound rotor motor, 7.5 HP, 230 volts, 3phase takes a line current of 18.4 ampere, when operating at rated output at an efficiency of 88%. Calculate the indication on the wattmeter when this is inserted to measure power by the T-method. The correct answer is: 3.179 kW 13. What is the purpose of the rheostat in ohmmeter? The correct answer is: Compensate aging battery of the meter 14. Two wattmeters are used to measure the power drawn by a balanced three-phase load

The rms value of a half-wave rectified

from a 440 V, three-phase source. The

symmetrical square wave current of 2 A is

wattmeters are connected in lines A and B and

The correct answer is: 2^1/2 A

reads 10 kW and -2.5 kW. When a capacitor in parallel with the load and the wattmeters

6. 7.

1000 kW is equal to how many is ergs/sec.

reconnected in lines B and C, the wattmeter in

The correct answer is: 1 x 10^13

line B reads 7.5 kW. What is the power factor

A 60 uF capacitor is connected in series with a

of the combined load?

400 ohm resistor. If the capacitor is initially

The correct answer is: 50%

uncharged, determine the resistor and

the CT ratio is 1200/5. The potential going into

constant for a suddenly applied source emf of

the wattmeter is 115 volts. What is the MW

120 volts.

indicated when the wattmeter reads 800 watts?

The correct answer is: 26.78 V, 93.22 V 8.

A light bulb having a tungsten filament draws

The correct answer is: 192 MW 16. If D is the electric flux density, then value of

0.5 amp at 110 volts. The cold resistance of the

electric intensity in air is

filament is 20 ohms at 20 deg C with

The correct answer is: D/(permittivity of free

temperature coefficient of resistance for tungsten at this temperature of 0.0005 per deg

space) 17. A 35 unit south pole is placed 1 inch to a 20

C. Determine the operating temperature of the

unit south pole. Determine the force between

bulb.

the poles.

The correct answer is: 2520 deg C 9.

15. At a 115 kV substation, the PT ratio is 100 and

capacitor voltages when t = 1.5 times the time

Induction instruments have found widest applications as

The correct answer is: 108.5, repulsion 18. The rms value of the voltage waveform v(t) = sin 10t + sin 20t is ____. The correct answer is: 1

19. Two point charges Q1 = 50 microcoulombs and Q2 = 10 microcoulombs are located at (-1, 1, 3)

The correct answer is: 44.7 volts 32. Which of the following is zero inside charge-

and (3, 1, 0) meters respectively. Find the

conducting spheres?

magnitude of the force on Q1.

The correct answer is: both A and B

The correct answer is: 4.9 N 20. An electronic measuring device that provides instantaneous visual indication of voltage

33. The unit of absolute permittivity of a medium is The correct answer is: Newton/meter 34. Capacitor of 30-microfarad capacitance is in

excursions

series with a coil across an 8,000 cycle supply.

The correct answer is: Oscilloscope

What inductance is required for resonance?

21. Find the current that flows through the filament of a 400 watt flat iron connected to a 220 volt

The correct answer is: 13.19 uH 35. Two metallic plates separated by 1 cm are

power line.

connected across a 12 V battery. A certain

The correct answer is: 500 mA

material is inserted completely filling the space

22. The current in an open circuit is The correct answer is: zero 23. What is the energy stored in a 50 uF capacitor if the impressed voltage is 220 volts? The correct answer is: 1.21 joules 24. Ten (10) kW is equal to ____ gram-cal/sec. The correct answer is: 2,388 25. The capacitor that stores the charge of 0.5 C at 10 volts has a capacitance of ____ farad. The correct answer is: 0.05 26. The force between two charges placed a given

between the plates and the charge on each plate observed to double. What is the dielectric constant of the plastic material? The correct answer is: 2 36. The positive terminal of a 6-V battery is connected to the negative terminal of a 12-V battery whose positive terminal is grounded. The potential at the positive terminal of the 6-V battery is ____ volt. The correct answer is: -12 37. In a cable capacitor, voltage gradient is

distance apart _____ as the relative permittivity

maximum at the surface of the

of the medium is increased

The correct answer is: conductor

The correct answer is: decreases 27. Point charges in air are located accordingly: Q1

38. Two spheres separated from each other by 10 m have charges of 0.001 Coulomb and 0.003

= 3 x 10^-8 C at (0, 0) meters, Q2 = 5 x 10^-8 C

Coulomb, respectively. In between the two

at (3, 0) meters and Q3 = -5 x 10^-8 C at (0, 4)

spheres is a point of zero electric field. What is

meters. Calculate the field intensity at (3, 4)

its distance from the 0.001 Coulomb sphere?

meters.

The correct answer is: 3.66 m

The correct answer is: 59.97 V/m 28. What is the typical full-scale deflection current

39. A 12 micro-farad capacitor charged at 500 Volts and a 6 micro-farad capacitor charged at

of a moving coil instrument?

250 Volts are connected in parallel. What is the

The correct answer is: 50 mA

potential difference in the combination?

29. In a cable with compound dielectric voltage gradient is inversely proportional to The correct answer is: both A and B 30. For the voltage waveform v(t) = 2 + cos (wt +

The correct answer is: 500 Volts 40. A 33 kilo ohms resistor is connected in a series parallel combination made up of a 56 kilo ohm resistor and a 7.8 kilo ohm resistor. What is the

180 deg) find the ratio of Vrms/Vave.

total combined resistance of these three

The correct answer is: 3/(2*2^1/2)

resistors?

31. A series circuit with 2 amperes flows through a 20 ohm resistor, 50 ohm inductive reactance

The correct answer is: 39067 ohms 41. An electric water heater has a rating of 1 kW,

and 60 ohm capacitive reactance. What is the

230 V. The coil used as the heating element is

supply voltage?

10 m long and has a resistivity of 1.724 x 10^-6

ohm-cm. Determine the required diameter of the wire in mils.

1.

measuring high power?

The correct answer is: 2.52 mils 42. Which of the following cannot be easily

The correct answer is: Bolometer

measured with a simple meter circuit? The correct answer is: Impedance

2.

43. What is the degree of exactness of

The correct answer is: 1.44 x 10^-3 J

value of the variable being measured? 3.

44. Four capacitors A, B, C and D are connected

The correct answer is: An ohmmeter

accumulated in A, B and C are equal to 2000, capacitance of the combination is known to be

4.

5.

The correct answer is: 1000 uC in parallel with an impedance Z2 = 12 + j6. The

series resistance required to operate the lamp

input reactive power is 2500 var lagging. What

from an 80 V supply.

is the total active power?

The correct answer is: 6 ohms

The correct answer is: 3025 W on a balanced three-phase source. If the

The hot resistance of an incandescent lamp is 10 ohms and the rated voltage is 50 V. Find the

45. An impedances Z1 = 2 + j4 ohms is connected

46. Three 10-ohm resistances are connected delta

A moving coil voltmeter measures The correct answer is: only dc voltages

35 uF, how much charge is accumulated in capacitor D?

Which type of meter requires its own power source?

across a 15-V DC source. The charges 750 and 1500 uC, respectively. If the total

A 20 uF capacitor is charged by a 12-V battery. What is the stored energy in the capacitor?

measurement when compared to the expected The correct answer is: Accuracy

What is the most accurate of all instruments for

6.

If a body is considered as a conducting sphere

equation of the phase Van =120 sin wt. What is

of 0.5 m radius, its capacitance to infinity is

the equation of the line current in line a?

The correct answer is: 55 pF

The correct answer is: 36 sin wt 47. For measuring DC voltage, the most accurate

7.

type of meter is the

2.5 x1 0^21 electrons pass in 10 seconds.

The correct answer is: D Arsonval

The correct answer is: 10 Amperes

48. A copper bar has a length of 20 ft., width of 4 inches and thickness of 0.5 inch. If the

Find the current in a conductor through which

8.

resistivity of copper is 10.37 ohms-CM/ft, what

What is the time constant of a 500 mH coil and a 3,300 ohm resistor in series?

is the resistance of the bar?

The correct answer is: 0.0015 sec

The correct answer is: 81.4 micro-ohms 49. A milliameter with full-scale deflection of 1 mA and a resistance of 25 ohms was used to measure an unknown current by shunting the meter with a 1-ohm resistor. The meter then

9.

Three identical capacitances, each of 450 uF, are connected in star. The value of capacitance

reads half-scale. What is the unknown value?

in each phase of the equivalent delta-

The correct answer is: 13 mA

connected load would be

50. At what on a meter movement are the most accurate reading taken? The correct answer is: Midscale

The correct answer is: 150 uF

The correct answer is: extend the range of ac instruments 16. A certain capacitor is charged at 48 volts after which its stored energy is 5.76 x 10^-2 joules. 10. An ac source of 200 Vrms supplies active power of 600 W and reactive power of 800

What is the capacitance of the capacitor? The correct answer is: 50 uF

VAR. The rms current drawn from the source is The correct answer is: 5 A 11. Three equal positive charges of 10 statcoulomb each are located at the vertices of an equilateral triangle of 2 cm leg. What is the

17. A constant voltage is applied to a series RL

magnitude of the force acting on each charge?

circuit at t = 0 by closing the switch. The

The correct answer is: 43.3 dynes

voltage across L is 25 volts at t = 0 and drops

12. A 5 microfarad capacitor is discharged

to 5 volts at t = 0.025 second. If L = 2 H, what

suddenly through a coil having an inductance

must be the value of R in ohms?

of 2 H and a resistance of 200 ohms. The

The correct answer is: 128.80

capacitor is initially charge to a voltage of 10

18. Three identical resistances, each of 15 ohms,

volts. Find the additional resistance required

are connected in delta across 400 V, 3-phase

just to be prevent oscillation.

supply. The value of resistance in each leg of

The correct answer is: 1065 ohms

the equivalent star-connected load would be

13. For medium, electric flux density is related to electric density E by the equation The correct answer is: D = (permittivity of free space*relative permittivity)E 14. Two heaters, rated at 1000 W, 250 volts each, are connected in series across a 250 volt, 50 Hz A.C. mains. The total power drawn from the

The correct answer is: 5 ohms 19. Find the dielectric constant to air The correct answer is: Approximately 1 20. _____ is used to store electrical energy in an electrostatic field. The correct answer is: A capacitor 21. The torque of a spring controlled ammeter

supply would be ____ watt.

varies as the square of the current thru it. If the

The correct answer is: 500

current of 5 amperes produces deflection of 90

15. The main purpose of using instrument transformer in a.c. measurements is to

degrees, the deflection in degrees for a current of 3 amperes is ____. The correct answer is: 32.4

22. Across a 230-V, 60 Hz power supply is a 15ohm non-inductive resistor. What is the

28. Induction instruments have found widest applications as

equation of the voltage and resulting current?

The correct answer is: watthour meter

The correct answer is: e = 325.5 sin 377t and i

29. If D is the electric flux density, then value of

= 21.6 sin 377t 23. How does a pointer of an underdamped ammeter behave? The correct answer is: Move slowly 24. The Norton equivalent of a circuit consists of a 2 A current source in parallel with a 4 ohm resistor. Thevenin equivalent of this circuit is a ____ volt source in series with a 4 ohm

electric intensity in air is The correct answer is: D/(permittivity of free space) 30. Which of the following safety rules should be observed while working on a live electric circuit? The correct answer is: both A and B 31. When an R-C circuit is currently connected

resistor.

across a d.c. voltage source, the initial rate of

The correct answer is: 8

change of capacitor current is

25. Two electrons in a vacuum experience a force of 2 x 10^-15 N. The correct answer is: 3.39 x 10^-7 m

The correct answer is: -Io/(damping factor) 32. A series RLC circuit with R = 1 k-ohm, L = 1 H and C = 6.25 uF is suddenly connected across a 24 V dc source. At t = 0, i = 0 and q = 0. Determine the current after 0.01 sec. The correct answer is: 5.40 mA

26. Four cubic meters of water is to be heated by means of four 1.5 kW, 230-V immersion heating elements. Assuming the efficiency of

33. A capacitor whose plates is 20 cm x 3.0 cm

the heater as 90%, determine the time required

and is separated by a 1.0-mm air gap is

in boiling the water if the initial temperature is

connected across a 12-V battery. Determine

20 degrees C and if all four elements are

the charge accumulated on each plate after a

connected in parallel.

long time.

The correct answer is: 69 hrs 27. When a 15 V square wave is connected across a 50 volt AC voltmeter, it will read ____.

The correct answer is: 6.4 x 10^-10 C 34. A power plant customer draws power at 220 volts from transformers on a pole. Current transformers with a ratio of 200/5 are used to

The correct answer is: 15 V

meter the electrical usage. What is the multiplier of the kW-hr and demand meters? The correct answer is: 40 35. A capacitor is rated 100 kVAR, 380 V, 50 Hz. What will its rating be at 60 Hz, 220 V? The correct answer is: 40 kVAR

40. An electronic measuring device that provides instantaneous visual indication of voltage excursions The correct answer is: Oscilloscope 41. Energy stored by a coil is doubled when its current is increased by ____ percent.

36. The force between two charges placed a given distance apart _____ as the relative permittivity of the medium is increased The correct answer is: decreases 37. The stator of a 440 V, 50 HP shunt motor is tested at 75 degrees C for its insulation resistance between terminals connected together and the ground frame. When a 50,000 ohm voltmeter is connected in series with a 600 V DC source, the meter indicates 125 V. Calculate the insulation resistance. The correct answer is: 190 kilo-ohms 38. The maximum voltage that can be applied to a

The correct answer is: 141.4 42. A coil takes apparent power and reactive power of 100 VA and 80 VAR, respectively. What is the Q factor of the coil? The correct answer is: 1.33 43. Which of the following instruments has its reading independent of the waveform and frequency of the ac supply? The correct answer is: hot-wire 44. A galvanometer has a resistance of 300 ohms. What is the ohmic resistance to make it read one is to ten?

capacitor without the capacitor breaking down or shorting The correct answer is: working voltage 39. Which of the following ammeters is the most sensitive? The correct answer is: 0 - 1 micro-ammeter

The correct answer is: 33.33 45. One kWh of energy equals nearly The correct answer is: 860 kcal 46. What is the resonant frequency of a circuit when L is 5 microhenrys and C is 9 picofarads are in series? The correct answer is: 23.7 MHz 47. Electric flux remaining from an electric charge of +Q coulomb is The correct answer is: Q 48. What is VOM?

The correct answer is: A combinational ohmmeter, milliammeter, and voltmeter

If relative permittivity of mica is 5, its absolute permittivity is >>>>>> . 5*(permittivity of free space) Which meter used dual triode tube and requires external power for operation >>> VTVM If a multiple capacitor has 10 plates, each of area 10 square cm, then>>>SERIES

49. A series RLC circuit is excited by an ac voltage v(t) = sin t. If L = 10 H and C = 0.1 F, then the peak value of the voltage across R will be

According to Gauss theorem, the surface integral of the normal component of the electric flux density D over a closed surface containing charge Q is >>>>>> q What test instrument will you use to make a modulated envelope visible? Logic pulser??

The correct answer is: 1 50. A.25 sin (314t + pi/3) 51. Select one:



52.

a. 10 sin (314t - pi/6)

53.

b. 5*(2^1/2)*sin (314t + pi/4)

54.

c. 5 sin (314t + pi/2)

A capacitor is charged with 0.23 watt-second of energy at a voltage of 48 volts. What is its capacitance? answer is 200 microfarad

 An instrument that measures small amount of current and is based on the electromagnetic principle. Gavlvanometer induction instruments have found widest applications as ---watthour meter An alternating voltage is given by v = 20 sin 157t. The frequency of the alternating voltage is ____. 25hz The objective of a capacitor is to --- Block DC and pass AC current If admittance Y = 0.06 - j0.08 mho, then conductance G equals >>>>>>>>> .06 A sine wave has a maximum value of 20 V. Its value at 135 degrees is >>>>>>> 14.14 A coil of 40 ohms resistance has an inductance of 100 mH and is connected in parallel with a 40 uF capacitor. What is the resonance frequency of the circuit?=======79.6

jcms