EE Reviewer

Question 1: EE Board 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 B. 0.20 ohm C. 0.25 ohm D. 0.30 ohm

Question 2: 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. 5Ω B. 4Ω C. 3Ω D. 2Ω

Question 3: EE Board 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 B. 145.7 ohms C. 147.5 ohms D. 157.4 ohms

Question 4: 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 B. 1.0 ohm C. 0.2 ohm D. 0.3 ohm

Question 5: EE Board April 1988 A Barangay power station supplies 60 kW to a load over 2,500 ft, 100 mm 2, two-conductors 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 B. 108 A C. 110 A D. 102 A

Question 6:

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A 120 V DC motor draws current of 100 A and is located 1000 ft from the supply source. If the diameter of the copper transmission line is 0.45 inch, what must be the voltage of the supply? A. 125.32 V B. 130.24 V C. 129.32 V D. 127.05 V

Question 7: EE Board October 1986 A 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 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 B. 590 V C. 585 V D. 590 V

Question 8: 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. 8Ω B. 4Ω C. 6Ω D. 10Ω

Question 9: A resistive coil draws 2 A at 110 V after operating for a long time. If the temperature rise is 55 0C above the ambient temperature of 20 0C, calculate the external resistance which must be initially connected in series with the coil to limit the current to 2 A. The temperature coefficient of the material of the coil is 0.0043 per 0C at 20 0C. A. 10.12 ohms B. 10.52 ohms C. 11.45 ohms D. 12.05 ohms

Question 10: A carbon resistor dissipates 60 W of power from a 120 V source at 20 0C. How much power will be dissipated in the resistor at 120 0C if connected across the same source? Assume the temperature coefficient of carbon at 20thC is -0.0005 per 0C. A. 61.50 W B. 65.21 W C. 62.34 W D. 63.16 W Posted by electricalengineeringreviewer at 11:41 PM 4 comments: Email ThisBlogThis!Share to TwitterShare to FacebookShare to Pinterest

DC ELECTRIC CIRCUITS - Day 4 Question 1: EE Board April 1981, EE Board October 1984

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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 B. 0.64 A C. 0.48 A D. 0.57 A

Question 2: An arc lamp takes 10 A 50 volts. A resistance R is to be place in series so that the lamp may burn correctly from a 110 V supply. Find the power wasted in this resistor. A. 800 watts B. 600 watts C. 700 watts D. 900 watts

Question 3: Conductor “x” of a certain material and a given cross section has a resistance of 0.1 ohm per meter and a temperature coefficient of 0.005 per 0C. Conductor “y” of another material and a given cross section has a resistance of 0.5 ohms per meter and a temperature coefficient of 0.001 per 0C. Is desired to make a coil having a resistance of 500 ohms and a temperature coefficient of 0.002 by using suitable lengths of the two wires connected in series. Calculate the required length of wire “x” A. 1225 m B. 1250 m C. 1240 m D. 1210 m

Question 4: EE Board 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 B. 0.26 ohm C. 0.23 ohm D. 0.03 ohm

Question 5: A high voltage DC transmission line delivers 1000 MW at 500 kV to an aggregate load over a distance of 900 km. Determine the voltage at the sending end. Assume the loop resistance of the line to be 1mΩ per km. A. 510.5 kV B. 505.2 kV C. 507.7 kV D. 503.6 kV

Question 6: EE Board April 1989

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It is required that a loading of 3 kW be maintained in a heating element at an initial temperature of 20 0C, 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 0C. Calculate the final temperature of the heating element. A. 345.43 0C B. 326.42 0C C. 336.84 0C D. 318.48 0C

Question 7: A 200-W, 110-V incandescent lamp has a filament having a temperature coefficient of resistance equal to 0.005 at 0C. If the normal operating temperature of the bulb is 2500 0C, how much current will the bulb draw at the instant it is turned on. Assume a room temperature of 20 0C. A. 29.42 A B. 18.37 A C. 22.31 A D. 28.21 A

Question 8: The power drawn by a resistive coil made of copper wire is 220 W at 100 V and 20 0C. Calculate the power consume by the coil at 115 V and 100 0C. The temperature coefficient of resistance at 20 0C is 0.00393. A. 175 W B. 211 W C. 183 W D. 225 W

Question 9: 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 B. 2.52 mils C. 3.21 mils D. 1.35 mils

Question 10: When two resistors A and B are connected in series, the total resistance is 36 ohms. When connected in parallel, the total resistance is 8 ohms. What is the ratio of the resistance R a to resistance Rb . Assume Ra