RURAL ELECTRIFICATION PROBLEM SET

Question 1: In the construction of an ammeter, a resistor is placed in parallel with the permanent magnet moving coil instrument. If the moving coil instrument has a resistance of 30 ohms and gives a full scale reading with a current of 0.01 amperes, what size resistor is needed in order to have the ammeter read a full-scale when measuring 0.03 amperes.

A) 200 ohms

B) 10,000 ohms

C) 15 ohms

D) 0.1 ohms

SOLUTION: https://youtu.be/46phy6Dycwk

Question 2: A 17 ohm resistor, a 0.095 Henry inductor and a 318 µfarad capacitor are connected in series across a 120 volt 60 Hz supply. What is the total impedance of the circuit?

A) 8.34 ohms

B) 35.8 ohms

C) 25.2 ohms

D) 32.3 ohms

SOLUTION: https://youtu.be/46phy6Dycwk

Question 3: A prony brake test of a motor gave the following data: Force = 2 lb, Length of arm = 1 ft, N (rpm) = 1720. The Electrical meter readings: Current = 11.4 amp;Voltage = 110;Power = 960 Watts. What is the actual power delivered by the motor as measured by the prony brake?

A) 3 hp

B) 0.66 hp

C) 1.3 hp

D) 5 hp

SOLUTION: https://youtu.be/46phy6Dycwk

Question 4: What is the efficiency of the motor in converting electric energy to mechanical energy in Question 3?

A) 75%

B) 95%

C) 63%

D) 51%

SOLUTION: https://youtu.be/46phy6Dycwk

Question 5: What is the power factor in Question 3?

A) 0.95

B) 0.83

C) 0.69

D) 0.76

SOLUTION: https://youtu.be/46phy6Dycwk

Question 6: A capacitance of 40 μF and a resistance of 100 ohms are connected in series across a 220-V, 60 Hz mains. Determine the impedance of the circuit.

A) 166

B) 83

C) 120

D) 42

SOLUTION: https://youtu.be/46phy6Dycwk

Question 7: Determine the voltage across the resistance in Question 6.

A) 18

B) 36.1

C) 183

D) 144

SOLUTION: https://youtu.be/46phy6Dycwk

Question 8: What is the angle between voltage and current in Question 6?

A) 25

B) 34

C) 53

D) 50

SOLUTION: https://youtu.be/46phy6Dycwk

Question 9: What is the power factor in Question 6?

A) 0.80

B) 0.60

C) 0.70

D) 0.83

SOLUTION: https://youtu.be/46phy6Dycwk

Question 10: What is the current I in the circuit shown below?

A) R3 / (R1R2 + R2R3 + R1R3)

B) VR3 / (R1R2 + R1R3 + R2R3)

C) VR2 / (R1R2 + R1R3 + R2R3)

D) VR2 / (R2 + R3 )

SOLUTION: https://youtu.be/46phy6Dycwk

Question 11: What is the current in the resistor R3?

A) 3.33 amps

B) 6.67 amps

C) 10.0 amps

D) 13.33

SOLUTION: https://youtu.be/46phy6Dycwk

Question 12: A 120 volt generator delivers 30 kilowatts to an electric furnace. The current supplied by the generator is about:

A) 500 amps

B) 4 amps

C) 100 amps

D) 250 amps

SOLUTION: https://youtu.be/46phy6Dycwk

Question 13:A 10 ohm resistor is connected in parallel with a capacitive reactance of 24 ohms. What is the total impedance?

A) 26.55 ohms

B) 13.73 ohms

C) 9.23 ohms

D) 14.56 ohms

SOLUTION: https://youtu.be/46phy6Dycwk

Question 14:How much energy is required to operate an 5 hp motor used every other day for 5 hours and a 500 watt lamp used daily for 4 hours a day, both during a 30-day month?

A) 195.9 kw-hrs

B) 339.6 kw-hrs

C) 27.8 kw-hrs

D) 368.6 kw-hrs

SOLUTION: https://youtu.be/46phy6Dycwk

Question 15:What is the current flowing in the center leg?

A) 4 amps

B) 6 amps

C) 5 amps

D) 3 amps

SOLUTION: https://youtu.be/46phy6Dycwk

Question 16:The potential across two points in a complex network is 50 volts. Eight amperes of current are flowing. What is the Thevenin equivalent circuit?

A) Figure A

B) Figure B

C) Figure C

D) Figure D

E) Figure E

SOLUTION: https://youtu.be/46phy6Dycwk

Question 17: A delta resistor network has Ra= 30 ohms, Rb= 10 ohms, and Rc= 20 ohms. What is the equivalent wye network?

A) 10 ohms, 5 ohms and 3.33 ohms

B) 6 ohms, 9 ohms and 10 ohms

C) 3 ohms, 6.66 ohms and 7 ohm

D) 5 ohms, 8 ohms and 3.33 ohms

SOLUTION: https://youtu.be/46phy6Dycwk

Question 18:A No. 10 AWG wire transmits a 220 V, 5-amp current through a distance of 2,000 ft. What is the voltage drop across the line?

A) 10 Volts

B) 20 volts

C) 15 volts

D) 25 volts

SOLUTION: https://youtu.be/46phy6Dycwk

Question 19:A 30 ohm resistor, a 0.095 Henry inductor and a 318 µfarad capacitor are connected in series across a 240 volt 60 Hz supply. What is the total impedance of the circuit? ?

A) 8.34 ohms

B) 40.68 ohms

C) 25.2 ohms

D) 32.3 ohms

SOLUTION: https://youtu.be/46phy6Dycwk

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