25  MCQs about Synchronous Motors:

1. The speed of a synchronous motor is determined by:
A. The frequency of the AC supply
B. the number of poles on the rotor
C. The excitation current
D. both the frequency of the AC supply and the number of poles on the rotor
Answer: (C)

2. The torque produced by a synchronous motor is proportional to:
A. The excitation current
B. the slip
C. The difference between the stator and rotor fluxes
D. the square of the excitation current
Answer: (C)

3. The slip of a synchronous motor is:
A. zero
B. positive
C. negative
D. cannot be determined without knowing the load
Answer: (A)

4. A synchronous motor can operate at:
A. lagging power factor
B. Leading power factor
C. Unity power factor
D. all of the above
Answer: (D)

5. The synchronous motor is a:
A. self-starting motor
B. non-self-starting motor
C. can be either self-starting or non-self-starting, depending on the design
D. cannot be used to power a load
Answer: (B)

6. The rotor of a synchronous motor is made of:
A. copper
B. aluminum
C. steel
D. permanent magnet material
Answer: (C)

7. The stator of a synchronous motor is made of:
A. copper
B. aluminum
C. steel
D. permanent magnet material
Answer: (A)

8. The synchronous motor is used in applications where:
A. A constant speed is required
B. A high starting torque is required
C. A low starting torque is required
D. Both a constant speed and a high starting torque are required
Answer: (A)

9. The synchronous motor is used in the following applications:
A. electric clocks
B. generators
C. induction motors
D. transformers
Answer: (A, B)

10. The synchronous motor is more efficient than the induction motor:
A. at all loads
B. at light loads
C. at heavy loads
D. cannot be determined without knowing the load
Answer: (B)

11. The synchronous motor is more expensive than the induction motor:
A. always
B. sometimes
C. never
D. cannot be determined without knowing the application
Answer: (B)

12. The synchronous motor is more reliable than the induction motor:
A. always
B. sometimes
C. never
D. cannot be determined without knowing the application
Answer: (B)

13. The synchronous motor is more maintenance-intensive than the induction motor:
A. always
B. sometimes
C. never
D. cannot be determined without knowing the application
Answer: (C)

14. The synchronous motor is used in applications where a constant speed is required, such as:
A. electric clocks
B. generators
C. induction motors
D. transformers
Answer: (A, B)

15. The synchronous motor is used in applications where a high starting torque is required, such as:
A. electric clocks
B. generators
C. induction motors
D. elevators
Answer: (D)

16. The synchronous motor is used in applications where a low starting torque is required, such as:
A. electric clocks
B. generators
C. induction motors
D. fans
Answer: (A)

17. The synchronous motor is more efficient than the induction motor at light loads:
A. true
B. false
C. cannot be determined without knowing the load
Answer: (A)

18. The synchronous motor is more efficient than the induction motor at heavy loads:
A. true
B. false
Answer: (A)

19. The synchronous motor is more expensive than the induction motor at light loads:
A. true
B. false
C. cannot be determined without knowing the application
Answer: (C)

20. The synchronous motor is more expensive than the induction motor at heavy loads:
A. true
B. false
C. cannot be determined without knowing the application
Answer: (B)

21. The synchronous motor is more reliable than the induction motor at light loads:
A. true
B. false
C. cannot be determined without knowing the application
Answer: (C)

22. The synchronous motor is more reliable than the induction motor at heavy loads:
A. true
B. false
C. cannot be determined without knowing the application
Answer: (B)

23. The synchronous motor is more maintenance-intensive than the induction motor at light loads:
A. true
B. false
C. cannot be determined without knowing the application
Answer: (C)

24. The synchronous motor is more maintenance-intensive than the induction motor at heavy loads:
A. true
B. false
C. cannot be determined without knowing the application
Answer: (B)

25. The V-curve of a synchronous motor shows the relationship between:
A. the excitation current and the speed
B. The excitation current and the torque
C. The torque and the speed
D. The power factor and the speed
Answer: (C)