EE review

1.To determine the polarity of the voltage drop across a resistor, it is necessary to know a. Value of current through the resistor b. Direction of current through the resistor c. Value of resistor d. EMFs in the circuit 2. In a delta network, each element has a value R. The equivalent value of each element in star network will be a. R/6 c. R/2 b. R/4 d. R/3 3. The efficiency of power transfer when maximum transfer of power occurs a. 100% c. 75% b. 80% d. 50% 4. A star circuit has each element of resistance R/2. The equivalent delta elements will be a. R/6 c. 2R b. 3/2 R d. 4R 5. The resistance of two wires is 25 ohms when connected in series and 6 ohms when connected in parallel. The resistance of each wire is a. 10 Ω, 15 Ω c. 5 Ω, 10 Ω b. 20 Ω, 30 Ω d. 10 Ω, 20 Ω 6. Four wires of the same material, the same cross-sectional area and the same length when connected in parallel give a resistance of 0.25 Ω. If the same four wires are connected in series, the effective resistance will be a. 1 Ω c. 3 Ω b. 2 Ω d. 4 Ω 7. Which of the following statement is true both for a series and a parallel dc circuit? a. Elements have individual currents c. Voltages are additive b. Currents are additive d. Power are additive 8. A 40 W bulb is connected in series with a room heater. If now the 40 W bulb is being replaced by 100 W bulb, the heater output will a. Decrease c. Remain the same b. Increase d. Heater will burn out 9. Three identical resistors are first connected in parallel and then in series. The resultant resistance of the first combination to the second will be a. 9 times c. 1/3 times b. 1/9 times d. 3 times 10. Which of the following can have negative temperature coefficient? a. Compounds of silver c. Metallic alloys b. Liquid metals d. Electrolytes 11. An ideal voltage source should have a. Large value of e.m.f. c. Zero source resistance b. Small value of e.m.f. d. Infinite source resistance 12. The circuit whose properties are the same in either direction is known as a. Unilateral circuit c. Irreversible circuit b. Bilateral circuit d. Reversible circuit 13. A cooper wire of unknown length has a diameter of 0.25 inch and a resistance of 0.28 ohm. By successive passes through drawing dies, the diameter of the wire is reduced to 0.05 inch.

Assuming that the resistivity of copper wire remains unchanged in the drawing process, determine the resistance of the reduced-size wire? a. 175 ohms c. 185 ohms b. 157 ohms d. 160 ohms

14.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 one end of the conductor according to the formula. ρ = 0.003 + 10⁻⁴l² ohm-cm? a. 1.0 ohm c. 1.0806 ohm b. 0.0806 ohm d. 1.5806 ohm 15. The resistance of a given electric device is 46 ohms at 25°C. If the temperature coefficient of resistance of the material is 0.004545 at 20°C. What is the temperature of the device when its resistance is 92 ohms? a. 200°C c. 250°C b. 225°C d. 275°C 16. A resistance of 8 ohms is connected in series with two resistances each of 12 ohms connected in parallel. What resistance should be shunted across this parallel combination so that the total current taken shall be 2.0 A with 20 V applied? a. 1 ohm c. 2 ohms b. 3 ohms d. 4 ohms 17. A certain source has a constant emf of 12.6 volts and an internal resistance of 0.15 ohm. What is the maximum load power taken by a load resistor connected across the terminals of the source? a. 254.6 watts c. 274.6 watts b. 284.6 watts d. 264.6 watts 18. A resistor B is connected across 220-volt supply. A voltmeter having a resistance of 12,000 ohms is connected between the center of the resistor and one side of the supply. It reads 100 volts. What is the value of R in ohms? a. 4500 ohms c. 4800 ohms b. 4600 ohms d. 4500 ohms 19. Two materials X and Y have temperature coefficients of resistance of 0.004 and 0.0004 respectively at a given temperature. In what proportion must X and Y be joined in series to produce a circuit having a temperature coefficient of resistance of 0.001? a. 1:5 c. 1:7 b. 1:10 d. 1:20 20. How many calories are developed in 1.0 minute in an electric heater which draws 5.0 A when connected to a 110-volt line? a. 7850.4 cal c. 7860.4 cal b. 7873.4 cal d. 7883.4 cal

21. It is required to heat 22.68 kg of water from 15°C to boiling point in 15 minutes. If the thermal efficiency of the heater is 80%. Find the current taken, the supply voltage being 220 V. a. 30.9 Amps c. 40.9 Amps b. 50.9 Amps d. 60.9 Amps 22. A voltage of 200 V is applied to a tapped resistor of 500 ohms. Find the resistance between two tapping points connected to a circuit needing 0.10 A at 25 V? a. 59 ohms c. 69 ohms b. 89 ohms d. 79 ohms 23. Two charge objects attract each other with a force F. If the charges on both objects are doubled with no change in separation, the force between them becomes a. 1/4 F₁ c. 1/5 F₁ b. 4 F₁ d. 5 F₁ 24. A 0.001 coulomb of charge is separated from a 0.003 coulomb charge by 10 meters. If P denotes the pointed zero electric field between the charges, determine the distance P and the 0.001 coulomb charges? a. 2.66 m c. 3.66 m b. 4.66 m d. 5.66 m 25.The attraction capacity of electromagnet will increase if the a. Core length increases c. Flux density decreases b. Core area increases d. Flux density increases 26. Laminated cores, in electrical machines are used to reduce a. Copper loss c. Hysteresis loss b. Eddy current loss d. All of the above 27. An inductive coil has a resistance of 9.5 ohms. A battery of 115 volts is suddenly connected to the coil. After the current has risen to 10 A, it is changing at the rate of 160 A/sec. What is the self inductance of the coil in mH? a. 125 c. 150 b. 175 d. 190 28. A fuel cell converts _______ energy into electrical energy. a. Chemical c. Solar b. Mechanical d. Magnetic 29. The rms value of a sine wave is 100 A. Its peak value is a. 70.7 A c. 150 A b. 141.4 A d. 282.8 A 30. In a pure capacitive circuit, if the supply frequency is reduced to 1/2, the current will a. Be reduced by half c. Be four times as high b. Be doubled d. Be reduced to one-fourth 31. The power factor of a series R-L-C circuit at its half-power points is a. Unity c. Leading b. Lagging d. Lagging or Leading 32. For the same load, if the power factor of load is reduced, it will a. Draw more current c. Same current but less power b. Less current d. Less current but more power 33. When A.C. flows through a resistance, then a. Current leads emf c. Current & emf are in-phase b. Current lags emf d. None of the above

34. A choke coil is used for controlling current in an a. AC circuit only c. Both AC and DC circuits b. DC circuit only d. Integrated circuit 35. 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 systems 36. A resistance R and a reactance X in series is connected in parallel with an inductive reactance of 300 ohms across terminal a and b. Determine the values of R and X in order that the impedance across a and b is a pure resistance of 150 ohms? a. 100 ohms c. 120 ohms b. 110 ohms d. 130 ohms 37. A coil of 40 ohms resistance and 30 ohms reactance are connected in parallel with a capacitance C to produce resonance. The source voltage is 100 volts. What is the power drawn by the circuit? a. 140 W c. 150 W b. 160 W d. 170 W 38. A parallel resonant circuit having L=100 micro henry and C=10 pico farads. If Q factor of the circuit is 50, what is the band width of the resonant circuit? a. 21.84 khz c. 31.84 khz b. 41.84 khz d. 51.84 khz 39.In the two wattmeter method of measuring power taken by a balanced 3-phase load, if the load power factor is 0.50, one of the wattmeters will read a. One half of total power c. 0.707 of total power b. 0.866 of total power d. Zero 40. 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 be easily changed d. It is simple arrangement 41. 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 unbalanced d. Neutral wire available does not carry any current 42. The minimum number of wattmeter/s to measure power in a 3-phase unbalanced starconnected load is a. One c. Three b. Two d. Four 43. 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

44. A single wattmeter is used to measure the power taken by a balanced 3-phase load. If the wattmeter reads 2580 watts, what is the total load power if the T-method is used? a. 2580 watts c. 5160 watts b. 1290 watts d. 3,870 watts 45. A 3-wire, 3-phase supply feeds a load consisting of three identical resistors. By how much is the load reduced if one of the resistors be removed when the load is wye connected? a. 25% c. 75% b. 50% d. 100% 46. Three equal resistors are connected in wye across 480-volts, 3-phase lines. The line current is 6 A. To what value the line voltage be changed to obtain the same line current with the resistors delta connected? a. 120 V c. 130 V b. 150 V d. 160 V 47. If a capacitor is connected across a dc source without a resistor, the time constant of the circuit is a. V/R c. 1/RC b. RC d. Zero 48. A capacitor having a capacitance of 30 micro farads is connected across 220 V dc source. The charging current will be least a. When the capacitor is half charged b. Initially c. When the capacitor is fully charged d. When capacitor is charged 63.2%

49. A resistor is connected across the terminals of a 20 micro farads capacitor which has been previously charged to a voltage of 500 volts. If the voltage falls to 300 volts in 0.50 minute, the resistance in meg-ohms of the resistor is equal to a. 1.94 meg-ohms c. 2.94 meg-ohms b. 3.94 meg-ohms d. 4.94 meg-ohms 50. The purpose of providing dummy coils in a generator is a. To enhance flux density b. To amplify voltage c. To provide mechanical balance for the rotor d. To reduce eddy currents 51. If dc generator fails to build up the probable cause could not be a. Imperfect brush contact b. Field resistance less than the critical resistance c. No residual magnetism in the generator d. Faulty shunt connections tending to reduce the residual magnetism 52. If a self excited dc generator after being installed, fails to build up on its first trial run, the first

thing to do is to a. Reverse the field connections b. Increase the field resistance c. Increase the speed of prime-mover d. Check armature insulation resistance 53. A dc shunt generator driven at a normal speed in the normal direction fails to build up armature voltage because a. The resistance of the armature is high b. There is no residual magnetism c. The field current is too small d. None of these 54. The simplest way to shift load from one shunt generator to the other running in parallel is to a. Adjust their field rheostats b. Use equalizer connection c. Add resistance in their armature circuit d. None of these 55. A 6-pole wave wound armature has 600 conductors. If the flux per pole is 20 mWb, at what speed must the armature be driven to generate 240 volts? a. 350 V c. 360 V b. 3800 V d. 400 V 56. A 20 kW compound generator works on full load with terminal voltage of 250 V. The armature, series, and shunt windings have resistances of 0.05 ohm, 0.025 ohm, and 100 ohms, respectively. If the machine is connected short shunt, the emf generated is nearest to a. 256.126 V c. 156.126 V b. 356.126 V d. None of the above 57. A belt driven 60 kW shunt-wound generator running at 500 rpm is supplying full load to a bus bar at 200 V. At what speed will it run if the belt breaks and the machine continue to run taking 5 kW from the bus bar? The armature and field resistances are 0.1 Ω and 100 Ω respectively. Brush contact drop may be taken as 2V. Neglect armature reaction. a. 221 rpm c. 321 rpm b. 421 rpm d. 521 rpm 58. If a DC motor is connected across the AC supply it will a. Run at normal speed b. Not run c. Run at lower speed d. Burn due to heat produced in the field winding by eddy currents 59.The speed of a DC shunt motor more than its full-load speed can be obtained by a. Decreasing the field current c. Decreasing the armature current b. Increasing the field current d. Increasing the armature current 60. If the speed of a DC shunt motor is increased the back emf of the motor will a. Decrease c. Remain the same b. Increase d. Becomes zero 61. Which loss in a DC generator does not vary with load as well as flux density? a. Copper loss c. Hysteresis loss b. Eddy current loss d. Windage loss 62. In case of DC shunt motors, the speed is dependent on back emf only because a. Back emf is equal to armature drop b. Armature drop is negligible

c. Flux is proportional to armature current d. Flux is practically constant in DC shunt motors 63. By looking at which part of the motor, it can be easily confirmed that a particular motor is DC motors? a. Frame c. Commutator b. Shaft d. Stator 64. In DC motor, which of the following can sustain the maximum temperature rise? a. Slip-rings c. Field winding b. Commutator d. Stator 65. As the load is increased, the speed of DC shunt motor will a. Reduce slightly c. Increase proportionately b. Increase slightly d. Remains unchanged 66. Which of the following method of speed control of DC machine will offer minimum efficiency? a. Voltage control method c. Armature control method b. Field control method d. All of the above 67. Which motor should not be started on no-load? a. Series motor c. Cumulatively compound motor b. Shunt motor d. Differentially compound motor 68. By providing a variable resistance across the series field (diverter) in a DC series motor, speeds above normal can be obtained because a. Armature current decreases c. Line current decreased b. Flux is reduced d. None of the above 69. A 220-V, 10-HP, dc shunt motor has armature and field resistances of 0.25 and 100 ohms respectively. The full load efficiency is 83%. Determine the value of starting resistance in order that the armature starting current will not exceed 200% of its full load value. a. 1.599 A c. 2.599 A b. 3.599 A d. 4.599 A 70. A shunt motor has an armature resistance of 0.20 ohm. The armature takes a current of 120 A from a 440-V source and running at 800 rpm. If the total torque developed is unchanged, determine the speed if the magnetic field is reduced to 60% of the initial value. a. 1182 rpm c. 1150 rpm b. 1282 rpm d. 1250 rpm 71. A 15 HP, 220-V shunt motor draws an armature current of 55 A at full load. The armature resistance including brushes is 0.25 ohm. Calculate the total resistance of a starting box which would permit this motor to develop a starting torque equal to twice that at full load. a. 1.75 ohms c. 2.75 ohms b. 3.75 ohms d. 4.75 ohms

72. A 220-V dc motor has Rs=0.40 Ω, Rsh=175 Ω, and Ra=0.40 Ω. The machine is connected short shunt compound to 220-V mains. Calculate HP developed in the armature when the armature current is 30 A.

a. 5.85 hp c. 6.85 hp b. 7.85 hp d. 8.85 hp 73. A 550-V long shunt compound motor has an armature resistance of 0.215 ohm and a series field resistance of 0.15 ohm. The full load speed is 1900 rpm when the armature current is 22 A. At what speed will the motor operate with no-load if the armature current drop to 3 A with a corresponding drop in flux to 88% of full-load value. a. 2086.7 rpm c. 2186.7 rpm b. 2050.7 rpm d. 2150.7 rpm 74. If the input to the prime-mover of an alternator is kept constant but the excitation is increased, then a. KVA will be lagging c. KW will be changed b. KVA will be leading d. The pf of the load remains constant 75. Two alternators are running in parallel. If the driving force of both the alternators is change, this will result in change in a. Frequency c. Generated voltage b. Back emf d. All of the above 76. The advantage of providing damper winding in alternators is a. Elimination of harmonic effects b. Provide a low resistance path for the currents due to unbalancing of voltage c. Oscillations are provided when tow alternators operate in parallel d. All of the above 77. The armature reaction of an alternator will be completely magnetizing in case the load power factor is a. Unity c. Zero lagging b. 0.707 d. Zero loading 78. Which type of protection is provided on a generator to protect against stator installation failure? a. Over-current relay c. Thermocouple actuated alarm b. Differential protection d. Reverse power relay 79. A 4-pole, 3-phase, 60-Hz, wye-connected alternator has 24 slots with 40 turns in each coil and sinusoidally distributed flux per pole of 63 mWb. What is the terminal voltage on open-circuit if the pitch factor is unity? a. 4493 V c. 4393 V b. 4293 V d. 4193 V 80. Which winding of the transformer has less cross-sectional area? a. Primary winding c. Low voltage winding b. Secondary winding d. High voltage winding 81. Open-circuit test on transformer is conducted to determine a. Hysteresis losses c. Core losses b. Copper losses d. Eddy current losses 82. In power transformers, the tappings are provided on a. High voltage side c. In the middle of both windings b. Low voltage side d. LV as well as on HV side 83. The efficiency in transformer is maximum at a. Full-load c. One-third the full-load b. Half-load d. No-load

84. In general, the most important point to keep under constant watch during t he operation of a transformers is it a. Primary voltage c. Exciting current b. Core loss d. Temperature 85. In a 25-KVA single-phase transformer the core loss and full load copper losses are respectively 320 and 380 watts. What is the efficiency at half load and 0.866 power factor? a. 76.3% c. 86.3% b. 96.3% d. 66.3% 86. Referring to problem 96 above, determine the load in KVA in which the efficiency is maximum? a. 12.94 kVA c. 22.94 kVA b. 32.94 kVA d. 42.94 kVA 87. Determine the all day efficiency of a 50 kVA distribution transformer having a full load efficiency of 94% and full load copper loss is just equal to the constant iron loss. The loading is as per the following schedule at unity power factor; No load for 10 hours, 25% of full load for 6 hours, half load for 5 hours, and full load for 3 hours. a. 78.46% c. 88.46% b. 98.46% d. 68.46% 88. A 5-kVA, 1000/100-V two winding transformer is used as an autotransformer by connecting the two windings such that it can supply a 1100-volt load. The maximum kVA that can be supplied to the load is a. 45 kVA c. 35 kVA b. 55 kVA d. 65 kVA 89. In any two phases for an induction motor are interchanged. a. The motor will run in reverse direction b. The motor will run in reduced speed c. The motor will not run d. The motor will burn 90. 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 ohm c. 5.185 x 10⁻⁵ ohm b. 13.8 x 10⁻⁶ ohm d. 2.96 x 10⁻⁵ ohm 91. Determine the resistance of a bus bar 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 ohm c. 3.431 x 10⁻⁵ ohm b. 4.312 x 10⁻⁴ ohm d. 1.075 x 10⁻⁴ ohm 92. One turn of a copper bar is produced by cutting a 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 ohm c. 17.22 x 10⁻⁶ b. 15.53 x 10⁻⁶ ohm d. 14.83 x 10⁻⁶ 93. Determine the resistance of a conductor 0.10 meter long, with a uniform diameter of 1.0 cm and having a resistivity which varies as a function of length L measured from one end of the conductor according to the formula: ρ 0.003 + 10⁻⁴ L² ohm-cm. a. 0.0852 ohm c. 0.0806 ohm b. 0.0915 ohm d. 0.0902 ohm 94. A coil has 6,000 turns of wire and a resistance of 380 ohms. The coil is rewound with the same quantity (weighs) 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 ohm 95.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 to 2.5 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 96. A one-meter rod of 2cm 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 97. 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 mm. What does its resistance become? a. 0.85 ohm c. 0.93 ohm b. 0.78 ohm d. 0.81 ohm 98. 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. 0.5R d. 0.25R 99. What is the size in square millimeter (mm²) is the cable of 250 MCM size? a. 118.656 mm² c. 112.565 mm² b. 126.675 mm² d. 132.348 mm² 100. 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 101. The resistance of a wire is 126.48 ohms at 100°C and 100 ohms at 30°C. Determine the temperature coefficient of copper at 0°C? a. 0.00427 c. 0.0256

b. 0.00615 d. 0.0356 102. Two heating elements which are 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 103. 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 104. The resistance of 120 meters of wire is 12 ohms. What is its conductance? a. 0.0521 mho c. 6 mhos b. 0.083 mho d. 12 mhos 105. A load of 10 ohms was connected to a 12-volt battery. This 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 106. 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 107. A Barangay power station supplies 60 kW to a load over 2,500 ft, 100mm², two-conductors copper feeder, the resistance of which is 0.078 ohm per 1000 ft. The bus bar voltage is maintained constant at 600 volts. Determine the load current? a. 105 A c. 110 A b. 108 A d. 102 A 108. The LRT car, 5 km distance from the Tayuman, takes 100 A over a 100 mm hard drawn copper trolley wire having a resistance of 0.270 ohm per km. The rail and the ground return have a resistance of 0.06 ohm per km. If the station voltage is 750 volts, what is the voltage of the car? a. 585 V c. 587 V b. 590 V d. 595 V 109. Two (2) 115 volts incandescent lamps A and B are connected in series across a 230 volts 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 110. If the resistor rated at 5 watts and 6 volts are connected across a battery with an opencircuit

voltage of 6 volts. What is the internal resistance of the battery if the resulting current is 0.8 amp? a. 0.30 ohm c. 0.23 ohm b. 0.26 ohm d. 0.03 ohm 111. It is required that a loading of 3kW be maintained in a heating element at an initial temperature of 20°C, a voltage of 220 volts 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 3kW 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 112. Three resistors of 10, 15 and 20 ohms each are connected in parallel. What is the total conductance? a. 0.217 mho c. 4.62 mhos b. 3.41 mhos d. 0.52 mho 113. Three resistors of 10, 15 and 20 ohms each are connected in parallel. What is the equivalent resistance? a. 45 ohms c. 0.22 ohm b. 17.2 ohms d. 4.62 ohm 114. A 5-ohm resistance is connected is parallel with a 10-ohm resistance. Another set, a 6ohm and an 8-ohm resistances are also connected in parallel. The two sets are connected in series. What is the equivalent resistance? a. 6.76 ohms c. 14.4 ohms b. 9.25 ohms d. 21.2 ohms 115. 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

116. A 10-ohm and a 20-ohm resistance are connected in parallel. Another resistance of 5ohm is connected in series with the two. If the supply voltage is 48 volts, what is the current through the 10-0hm resistance? a. 3.21 A c. 4.02 A b. 2.74 A d. 5.72 A 117. 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 118. An electric kettle was marked 500 watts, 230 volts found to take 15 minutes to bring 1 kilogram of water at 15 degree celcius to boiling point. Determine the heat efficiency of the kettle. a. 79.1% c. 72.4% b. 75.3% d. 74.8% 119. A process equipment contains 100 gallons of water at 25 degree celcius. 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 120. A total of 0.8 kg of water at 20 degree celcius is placed in a 1-kW electric kettle. How long in minutes is needed to raise the temperature of the water to 100 degree celcius? a. 4.46 min. c. 6.34 min. b. 5.32 min. d. 4.56 min. 121. How many calories does an electric heater of 100 watts generate per second? a. 10 c. 1000 b. 23.88 d. 42.25 122. 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 123. 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 ⁰F c. 133.56 ⁰F b. 125.42 ⁰F d. 128.33 ⁰F 124. 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 ⁰C c. 72.6 ⁰C b. 68.4 ⁰C d. 42.6 ⁰C 125. 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 boiling the water if the initial temperature is 20°C and if all elements are connected in parallel. a. 71 hrs c. 69 hrs b. 63 hrs d. 66 hrs 126. A circuit consisting of three resistors rated 10-ohms, 15-ohms, and 20-ohms are connected in delta. What would be the resistances of the equivalent wye connected load? a. 0.30, 0.23 and 0.15 ohm c. 3.33, 4.44 and 6.66 ohms b. 3.0, 4.0 and 5.0 ohms d. 5.77, 8.66 and 11.55 ohms 127. The equivalent wye element of 3 equal resistors each equal to R and connected in delta is? a. R c. R/3

b. 3/2 R

d. 3R

128. 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 129. 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 volts station draws 200 A from the line. How much is the current supplied by each station? a. 133.33 A, 66.67 A c. 117.44 A, 82.56 A b. 123.67 A, 76.33 A d. 125.54 A, 63.05 A 130. A lead storage 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. If the two batteries together delivers 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 131. In Manila, the LRT runs between Gil Puyat Station and Tayuman Station, which is 4 km ap art 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, 128 A 132. An LRT car, 5 km distance from the Tayuman, takes 100 A over a 100 mm hard drawn copper trolley wire having a resistance of 0.270 ohm per km. The rail and the ground return has a resistance of 0.06 ohm per km. If the station voltage is 750 volts, what is the efficiency of transmission? a. 78% c. 74% b. 81% d. 79% 133. 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 134. 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

135. A 120 volts battery having an internal resistance of 0.5 ohm, is connected through a line resistance of 9.5 ohms to a variable load resistor. What maximum power will the battery deliver to the load resistor? a. 36 W c. 630 W b. 63 W d. 360 W 136. 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 feet. The bus bar voltage is maintained constant at 600 volts. Determine the maximum power which can be transmitted? a. 230.77 kW c. 242.73 kW b. 220.35 kW d. 223.94 kW

137. 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 138. 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 139. Twelve identical wires of resistance 6 ohms each are arranged to form the edge of a cube. A current of 40mA is led into the cube at one corner and out at the other diagonally opposite corner. Calculate the potential difference developed between these corners? a. 0.20 volt c. 0.22 volt b. 0.28 volt d. 0.24 volt 140. Three equal positive charges of 10 statcoulombs each are located at the vertices of an equilateral triangle of 2 cm leg. What is the magnitude of the force acting on each charge? a. 12.5 dynes c. 43.3 dynes b. 25 dynes d. 50 dynes 141. Two point charges 10 cm apart exert a force of 1 x 10⁻³ grams on each other. If the charges are the same value, what is the value of each charge in statcoulombs? a. 8.90 statcoulombs c. 6.90 statcoulombs b. 9.90 statcoulombs d. 7.90 statcoulombs 142. Two electrons in a vacuum experienced a force of 2 x 10⁻¹⁵ N. How far apart are the electrons? a. 0.48 x 10⁻⁷ m c. 3.39 x 10⁻⁷ m b. 2.84 x 10⁻¹² m d. 5.05 x 10⁻¹² m 143. Two point charges of 2 C and a 5 C are 10 meters apart. A third point charge of 6 C is placed between them. At what distance from the 5 C charge must the 6 C charge is placed, in such a way that it would stay in equilibrium?

a. 6.125 m c. 6.025 m b. 5.365 m d. 5.256 m 144. Two spheres separated from each other by 10 meters have charges of 0.001 coulomb and 0.003 coulomb respectively. In between the two spheres is a point of zero electric field. What is the distance from the 0.001 coulomb sphere? a. 6.34 m c. 2.24 m b. 7.78 m d. 3.66 m 145. Two metallic plates separated by 1 cm are connected across a 12 volt battery. A certain plastic material is inserted completely filling the space between the plates and the charge on each plate observed to double. What is the dielectric constant of the plastic material? a. 0.5 c. 4 b. 2 d. 6 146. Calculate the capacitance between two parallel plates each of which is 100 cm² and 2 mm apart in air? a. 0.443 x 10⁻¹² F c. 0.452 x 10⁻¹² F b. 0.515 x 10⁻¹² F d. 0.502 x 10⁻¹² F 147. A parallel plate capacitor is made of 350 plates, separated by paraffined paper 0.0010 cm thick (k=2.5). The effective size of the plate is 15 by 30 cm. What is the capacitance of this capacitor? a. 35 x 10⁻⁶ F c. 140 x 10⁻⁶ F b. 15 x 10⁻⁶ F d. 70 x 10⁻⁶ F 148. A capacitor is charged with 0.23 watt-second of energy at a voltage of 48 volts. What is its capacitance? a. 180 x 10⁻⁶ F c. 200 x 10⁻⁶ F b. 240 x 10⁻⁶ F d. 220 x 10⁻⁶ F 149. A 20 micro-farad capacitor is charged by a 12 volts battery. What is the stored energy in the capacitor? a. 1.07 x 10⁻³ J c. 2.88 x 10⁻³ J b. 2.88 x 10⁻² J d. 1.44 x 10⁻³ J 150. A parallel plate capacitor with air between its plate is charged until the potential difference V appears across it. Another capacitor having hard rubber (dielectric constant = 3) between its plates but otherwise identical, is also charged to the same potential difference. If the energy of the first capacitor is W, that of the second is ____? a. 9W c. W b. W/3 d. 3W 151. The result of capacitance C₁ = 6 microfarads and C₂ connected in series is 3 microfarads. Capacitor C₂, in microfarad is ___? a. 3 c. 8 b. 4 d. 6 152. A condenser of 1 microfarad capacitance is charged to 100 volts and then disconnected from

power supply. A second but uncharged capacitor of 3 microfarad is then connected across the first capacitor. The voltage across the parallel combination is ___? a. 66 2/3 volts c. 25 volts b. 45 volts d. 110 volts 153. Three capacitors A, B, and C are charged as follows: A = 10 microfarads, 100 volts; B = 15 microfarads, 150 volts; C = 25 microfarads, 200 volts. They are connected in parallel with terminals of like polarity together. What is the voltage across the combination? a. 150 volts c. 185 volts b. 120 volts d. 165 volts 154. A coaxial cable has a 10-mm diameter inside conductor and a metallic sheath with an inside diameter of 20 mm. If the insulating medium has a dielectric constant, K=2, and a permittivity of 1.113 x 10⁻¹⁰, what is the capacitance between the conductor and the shield per km? a. 0.1605 microfarad/km c. 0.0803 microfarad/km b. 0.8036 microfarad/km d. 0.0403 microfarad/km 155. A lead sheath cable for underground service has a copper conductor (diameter = 0.350 inch) surrounded by 0.20 inch wall of rubber insulation. Assuming the dielectric constant of 4.3 for rubber, calculate the capacitance of the cable per mile length? a. 1.01 microfarad/mile c. 0.76 microfarad/mile b. 0.504 microfarad/mile d. 0.252 microfarad/mile 156. The force acting on a pole of 3 Wb is 12 N. The magnitude intensity of the magnetic field is ________? a. 4 N/Wb c. 36 N/Wb b. 12 N/Wb d. None of the above 157. The reluctance of a non-magnetic circuit is 12 units. How much flux will be set up if surrounded by a coil 600 turns carrying a current of 3 Amperes? a. 150 c. 50 b. 16.67 d. 200 158. If a current of 5 amperes flows through a long wire of radius 0.004 meter, what is the flux density (H) produced 0.02 meter away from the surface of the wire? a. 19.70 AT/m c. 66.34 AT/m b. 39.80 AT/m d. 33.17 AT/m 159. The relative permeability of certain silicon steel is 4500. A certain magnetic loop consists of a silicon steel of 10 cm², 20 cm long and an air gap of ¼ cm. What is the reluctance of the magnetic circuit? a. 2.54 x 10⁻² c. 6.44 x 10⁻⁴ b. 6.44 x 10 ⁻³ d. 2.54 x 10⁻³ 160. A certain laminated steel core has a permeability of 3000. The length is 5 cm and the cross section is 2 square cm. What is its reluctance? a. 7500 c. 1200 b. 8.33 x10⁻⁴ d. 2.5

161. A magnetic circuit consists of silicon steel of 3000 permeability, of 10 cm length and a cross section of 1.5 square cm and an air gap of the same cross-section and of 2 cm length. A ½-ampere current flows through the 5000-turn coil. What is the field intensity at the air gap? a. 250 oersted c. 2262 oersted b. 795 oersted d. 1567 oersted 162. A magnetomotive force is supplied by a current of one ampere through 100 turns. The magnetic circuit consists of a steel core of 1000 permeability, 10 cm long and 4 square cm area and an air gap one cm long. What is the field intensity at the air gap? a. 12.25 oersted c. 100.53 oersted b. 497.66 oersted d. 124.4 oersted 163. A magnetic circuit consists of silicon steel of 3000 permeability and an air gap. The length of the steel core is 10 cm and the air gap is 2 cm. Both have the same cross-section of 1.5 square cm. A current of ½ ampere flows through the windings to produce 2351 maxwells flux. How many turns are there in the coil? a. 4120 turns c. 2500 turns b. 5000 turns d. 1250 turns 164. A permanent magnet loudspeaker is equipped with a 10 ohm, 10 turns voice coil wound on a tube 1 inch in diameter. The flux density in the air gap is 10,000 lines per square inch. If the impedance of the voice coil is a pure resistance, what will be the maximum thrust delive red to the core if the impressed signal is 20dB above 0.005 watt? a. 0.0336 N c. 0.0276 N b. 0.0116 N d. 0.0532 N 165. A small single-phase transformer has 10.2 watts at no-load. The core has a volume of 750 cubic cm. The maximum flux density is 10,000 gauss and the hysteresis constant of the core is 5 x 10⁻⁴. Using the Steinmetz law to find the hysteresis, determine the eddy current loss? a. 4.55 W c. 3.55 W b. 5.55 W d. 2.55 W 166. A magnetic coil produces 100,000 maxwells with 2,000 turns and with a current of 2 amperes. The current is cut-off and the flux collapses in 0.01 second. What is the average voltage that will appear across the coil? a. 20 kV c. 2,000 kV b. 200 kV d. 2 kV 167. A magnet, which generates 800 maxwells of flux, is inserted through a coil of 1000 turns. It is then withdrawn within 0.15 second. What is the voltage that appears across the coil? a. 0.22 V c. 533 V b. 53.3 V d. 0.0533 V 168. A conductor, 50 mm long, moves at a velocity of 2.5 meters per second across a magnetic field of 0.90 Wb/m². What is the voltage generated? a. 0.125 V c. 0.1125 V b. 0.0648 V d. 0.072 V 169. A piece of conductor 10 cm long moves a magnetic field of 10,000 gauss at a velocity of 120

cm/sec. What voltage appears across the conductor? a. 0.24 V c. 60 V b. 0.12 V d. 120 V

170. What is the coefficient of coupling of two coils whose mutual inductance is 1 H and whose selfinductance are 1.2 and 2 H? a. 1.549 c. 0.645 b. 2.400 d. 0.912 171. The total inductance of two coils, A and B when connected in series aiding is 0.5 H and 0.2 H when connected in series opposing. Coil A when isolated from coil B has a self-inductance of 0.2 H. Calculate the self-inductance of coil B? a. 0.16 H c. 0.20 H b. 0.12 H d. 0.15 H 172. The energy (Wₒ) stored in a coil is dependent in the inductance (L) of the coil and the current flowing. If the inductance were doubled with the same current flowing, what would be the resulting stored energy? a. 2.0 Wₒ c. 1.0 Wₒ b. 0.5 Wₒ d. 4.0 Wₒ 173. A 6.0 H coil whose resistance is 12 ohms is connected in series with a 24 ohms resistor and to a 144 volts battery and a switch. The switch is closed at t=0. Determine the energy stored in the magnetic field at steady state? a. 50 J c. 52 J b. 48 J d. 46 J 174. Two coils of inductances 4 and 6 Henry are connected in parallel. If their mutual inductance is 3 Henry, calculate the equivalent inductance of the combination if mutual inductance assist and if mutual inductance opposes the self-inductance respectively? a. 2.4 H and 1.4 H c. 6.25 H and 2.75 H b. 3.75 H and 0.94 H d. 16 H and 4 H 175. What is the wavelength of a carrier wave with a frequency of 100 megahertz? a. 3.0 m c. 1.5 m b. 7.5 m d. 6.0 m 176. 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 177. 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 178. A wire carries a current, i = 3 cos 314t amperes. What is the average current over 6 seconds? a. 0 A c. 3.0 A

b. 1.5 A d. 0.523 A 179. Three loads, units A, B and C are connected in parallel and take currents that are respectively 12, 10 and 15 Amperes. 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. 28.33 A c. 26.46 A b. 30.21 A d. 32.10 A 180. An industrial coil has a resistance of 32 ohms and a reactance of 24 ohms and rated 440 volts at 60 hertz. A factory will connect the coil to 440 volts, 5o hertz supply. Solve for the value of a series resistor needed to avoid over-current condition? a. 2.07 ohms c. 2.44 ohms b. 2.64 ohms d. 2.25 ohms 181. Across 230 volts, 60 hertz power supply is a 15 ohm non-inductive resistor. What is the equation of the resulting current? a. 21.68 sin 377t c. 15.33 sin 377t b. 26.55 sin 377t d. 28.16 sin 377t 182. Two relays each with 20 ohms resistance and 0.16 henry inductance are connected in series. What is the equivalent impedance? a. 20 + j102.2 ohms c. 40 + j120.63 ohms b. 20 + j95.32 ohms d. 40 + j25.32 ohms 183. An inductive coil takes a current takes a current of 2 amperes and consumes 160 watts when connected to a 240 volts AC supply. A second coil when connected across the same supply takes 3 amperes and 500 watts. Find the total power when the two coils are connected in series to this supply? a. 144.56 watts c. 150.22 watts b. 134.31 watts d. 128.35 watts 184. A coil draws 1875 watts when connected to a 150 volts dc source. It consumes 3072 watts when used on 240 volts, 60 hertz AC source. Find the inductance of the coil? a. 0.0255 H c. 0.0153 H b. 0.0341 H d. 0.0240 H 185. A current of 10 amperes and a power-factor of 0.8 lagging is taken from a single phase 250 volts supply. The reactive power of the system is? a. 1500 c. 2500 b. 2000 d. None of these 186. A resistor of 6 ohms and n unknown impedance coil in series draws 12 amperes from 120 volts, 60 hertz line. If the real power taken from the line is 1152 watts, what is the coil inductance? a. 15.9 mH c. 20 mH b. 10 mH d. 1.59 mH 187. Determine the power angle in the series circuit which consists of R=25 ohms. L=0.2 henry across a power supply of 200 volts, 30 hertz? a. 36.4° c. 46.4° b. 52.4° d. 56.4°

188. The impedance coil absorbs 250 watts when connected across 220 volts, 60 hertz mains. It is then connected across 110 volts, 25 hertz mains and also absorbs 250 watts. What is the inductance of the coil? a. 0.125 H c. 0.154 H b. 0.149 H d. 0.163 H 189. An impedance coil takes 10 A and absorbs 250 W when connected across a 220 V, 60 Hz source. What power will it absorb when connected across 110 V, 25 Hz mains? a. 539 W c. 439 W b. 239 W d. 339 W 190. An industrial coil has a resistance of 32 ohms and a reactance of 24 ohms and rated 440 volts at 60 Hz. A factory will connect the coil to a 440 V, 50 Hz supply. How much percentage overcurrent will the coil suffer? a. 5% c. 6% b. 10% d. 8% 191. A 25-ohm resistor connected in series with a coil of 50 ohm resistance and 150 mH inductance. What is the power factor of the circuit? a. 85% c. 90% b. 80% d. 75% 192. The ohmic resistance of a large magnetic contactor is measured to be 20 ohms. A 230 V is impressed on the contactor and the current is taken as 3.2 A. Neglecting core loss, determine the inductance of the contractor in mH? a. 261 c. 183 b. 315 d. 251

193. A load of 20 + j35 ohms is connected across a 220 volts source. Determine the power factor And the VARS. a. 49.6%, 1042 VARS c. 52.2%, 1023 VARS b. 85.3%, 975 VARS d. 42.3%, 1087 VARS 194. Find the total impedance in rectangular for the following three series impedances: 12