Power Systems MCQs | Part 4 | Diploma in Electrical Engineering

This is Part 4 of 30 MCQs on Power Systems for the Diploma in Electrical Engineering. This set of 30 MCQs will test your knowledge. Each question focuses on different aspects of power systems. Use these questions to prepare for exams.

1. Calculate the load current in a single-phase circuit with a load of 2 kW and a voltage of 230 V.

A. 7.8 A B. 8.7 A C. 9.4 A D. 10.1 A

2. What is the power factor of a system with a real power of 500 W and an apparent power of 600 VA?

A. 0.75 B. 0.80 C. 0.83 D. 0.86

3. Determine the synchronous speed of a 4-pole motor operating at 50 Hz.

A. 1200 RPM B. 1500 RPM C. 1800 RPM D. 2000 RPM

4. A 3-phase, 400 V system supplies a balanced load of 30 kW at a power factor of 0.8 lagging. Calculate the line current.

A. 50.4 A B. 52.1 A C. 54.3 A D. 56.2 A

5. Calculate the total impedance in a series circuit with a resistance of 4 ohms and a reactance of 3 ohms.

A. 5 ohms B. 6 ohms C. 7 ohms D. 8 ohms

6. A power system delivers 100 MW with a loss of 10 MW. What is the efficiency of the system?

A. 88% B. 90% C. 92% D. 94%

7. Determine the voltage drop in a 5 km transmission line with a resistance of 0.2 ohms per km and a current of 100 A.

A. 100 V B. 150 V C. 200 V D. 250 V

8. A transformer has a primary voltage of 11 kV and a secondary voltage of 400 V. Calculate the turns ratio.

A. 25:1 B. 27.5:1 C. 30:1 D. 32.5:1

9. What is the phase angle difference in a 3-phase system with a power factor of 0.9 lagging?

A. 25.8° B. 26.8° C. 27.8° D. 28.8°

10. A synchronous generator has an induced emf of 240 V and a synchronous reactance of 10 ohms. Calculate the current if the terminal voltage is 230 V.

A. 1.0 A B. 1.2 A C. 1.4 A D. 1.6 A

11. Calculate the reactive power in a circuit with a real power of 500 W and an apparent power of 600 VA.

A. 300 VAR B. 400 VAR C. 500 VAR D. 600 VAR

12. A 100 MVA transformer has a per-unit impedance of 0.1. What is its actual impedance in ohms if the base impedance is 5 ohms?

A. 0.5 ohms B. 1.0 ohms C. 1.5 ohms D. 2.0 ohms

13. A transmission line has a series impedance of 0.1 + j0.2 ohms per km. Calculate the total impedance for a 50 km line.

A. 5 + j10 ohms B. 6 + j12 ohms C. 7 + j14 ohms D. 8 + j16 ohms

14. Determine the line-to-line voltage in a balanced 3-phase system with a line current of 10 A and a phase impedance of 5 ohms.

A. 75.5 V B. 86.6 V C. 95.8 V D. 100.0 V

15. A generator supplies a load of 20 MW at a power factor of 0.9 lagging. Calculate the reactive power.

A. 9.7 MVAR B. 10.7 MVAR C. 11.7 MVAR D. 12.7 MVAR

16. Calculate the base current for a system with a base power of 50 MVA and a base voltage of 220 kV.

A. 100 A B. 113 A C. 125 A D. 227 A

17. A transformer has an efficiency of 95%. If the input power is 200 kW, what is the output power?

A. 185 kW B. 190 kW C. 195 kW D. 200 kW

18. Calculate the power factor of a circuit with a real power of 800 W and a reactive power of 600 VAR.

A. 0.6 B. 0.7 C. 0.8 D. 0.9

19. Determine the total capacitance of three capacitors in series with capacitances of 10 μF, 20 μF, and 30 μF.

A. 5.45 μF B. 6.67 μF C. 8.18 μF D. 9.09 μF

20. Calculate the line-to-neutral voltage in a balanced 3-phase system with a line-to-line voltage of 400 V.

A. 220 V B. 230 V C. 240 V D. 250 V

21. A 10 kW load is connected to a 400 V, 3-phase supply. Calculate the current drawn by the load.

A. 12.5 A B. 14.4 A C. 16.2 A D. 18.0 A

22. A motor draws 30 A from a 415 V supply and operates at a power factor of 0.85. Calculate the real power consumed by the motor.

A. 8.3 kW B. 10.6 kW C. 11.5 kW D. 12.8 kW

23. Determine the resonant frequency of a series RLC circuit with L = 2 H and C = 0.5 μF.

A. 159.2 Hz B. 250.0 Hz C. 318.3 Hz D. 636.6 Hz

24. A power plant generates 500 MW with an efficiency of 40%. Calculate the input power required.

A. 1000 MW B. 1100 MW C. 1200 MW D. 1300 MW

25. Calculate the maximum demand of a system with a connected load of 150 kW and a demand factor of 0.75.

A. 100 kW B. 112.5 kW C. 125 kW D. 137.5 kW

26. A synchronous motor operates with a field current of 10 A and produces a back emf of 230 V. Calculate the generated emf if the field current is increased to 12 A.

A. 276 V B. 288 V C. 300 V D. 312 V

27. A transmission line has a shunt capacitance of 0.1 μF per km. Calculate the total capacitance for a 200 km line.

A. 10 μF B. 15 μF C. 20 μF D. 25 μF

28. Calculate the power loss in a transmission line with a resistance of 2 ohms and a current of 50 A.

A. 200 W B. 300 W C. 400 W D. 500 W

29. A capacitor is charged to 100 V and has a capacitance of 50 μF. Calculate the energy stored in the capacitor.

A. 0.25 J B. 0.50 J C. 0.75 J D. 1.0 J

30. Determine the short-circuit current if a 100 MVA transformer with a 10% impedance experiences a fault.

A. 10 kA B. 15 kA C. 20 kA D. 25 kA

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Thank you for going through Part 4 of MCQs on Power Systems for the Diploma in Electrical Engineering”. Review the questions regularly. Stay updated with power system concepts. Keep practicing and learning.

30 MCQs on Power Systems (Part 4) | Diploma in Electrical Engineering