## Multiple Choice Questions (MCQ) on Single Phase Motors for Electrical Engineering

1. In a split phase motor
(a) the starting winding is connected through a centrifugal switch
(b) the running winding is connected through a centrifugal switch
(c) both starting and running windings are connected through a centrifugal switch
(d) centrifugal switch is used to control supply voltage

Ans: a

2. Which of the following motor will give relatively high starting torque ?
(a) Capacitor start motor
(b) Capacitor run motor
(c) Split phase motor

Ans: a

3. Which of the following motor will have relatively higher power factor ?
(a) Capacitor run motor
(c) Capacitor start motor
(d) Split phase motor

Ans: a

4. In a shaded pole motor, the shading coil usually consist of
(a) a single turn of heavy wire which is in parallel with running winding
(b) a single turn of heavy copper wire which is short-circuited and carries only induced current
(c) a multilayer fine gauge copper wire in parallel with running winding
(d) none of the above

Ans: b

5. If a particular application needs high speed and high starting torque, then which of the following motor will be preferred ?
(a) Universal motor
(c) Capacitor start motor
(d) Capacitor start and run motor

Ans: a

6. The value of starting capacitor of a fractional horse power motor will be
(a) 100 uF
(b) 200 uF
(c) 300 uF
(d) 400 uF

Ans: c

7. In repulsion motor direction of rotation of motor
(a) is opposite to that of brush shift
(b) is the same as that of brush shift
(c) is independent of brush shift

Ans: b

8. In a single phase motor the centrifugal switch
(a) disconnects auxiliary winding of the motor
(b) disconnects main winding of the motor
(c) reconnects the main winding the motor
(d) reconnects the auxiliary winding of the motor

Ans: a

9. The running winding of a single phase motor on testing with meggar is found to be ground. Most probable location of the ground will be
(a) at the end connections
(b) at the end terminals
(c) anywhere on the winding inside a slot
(d) at the slot edge where coil enters or comes out of the slot

Ans: d

10. Which of the following motors is used in mixies ?
(a) Repulsion motor
(b) Reluctance motor
(c) Hysteresis motor
(d) Universal motor

Ans: d

11. Which of the following motors is inherently self starting ?
(a) Split motor
(c) Reluctance motor
(d) None of these

Ans: b

12. The direction of rotation of an hysteresis motor is determined by
(b) position of shaded pole with respect to main pole
(c) retentivity of the rotor material
(d) none of these

Ans: b

13. Short-circuiter is used in
(a) repulsion induction motor
(b) repulsion motor
(c) repulsion start induction run motor
(d) none of the above

Ans: c

14. The range of efficiency for shaded pole motors is
(a) 95% to 99%
(b) 80% to 90%
(c) 50% to 75%
(d) 5% to 35%

Ans: d

15. For which of the applications a reluctance motor is preferred ?
(a) Electric shavers
(b) Refrigerators
(c) Signalling and timing devices
(d) Lifts and hoists

Ans: c

16. The motor used on small lathes is usually
(a) universal motor
(b) D.C. shunt motor
(c) single-phase capacitor run motor
(d) 3-phase synchronous motor

Ans: c

17. Which of the following motors is preferred for tape-recorders ?
(b) Hysteresis motor
(c) Two value capacitor motor
(d) Universal motor

Ans: b

18. A schrage motor can run on
(a) zero slip
(b) negative slip
(c) positive slip
(d) all of the above

Ans: d

19. Single phase induction motor usually operates on
(a) 0.6 power factor lagging
(b) 0.8 power factor lagging
(d) unity power factor

Ans: a

20. In a two value capacitor motor, the capacitor used for running purposes is
(a) air capacitor
(b) paper spaced oil filled type
(c) ceramic type
(d) a.c. electrolytic type

Ans: b

21. In A.C. series motor compensating winding is employed to
(a) reduce the effects of armature reaction
(b) increase the torque
(c) reduce sparking at the brushes
(d) none of the above

Ans: c

22. In case of a shaded pole motor the direction of rotation of the motor is
(a) from main pole to shaded pole
(b) from shaded pole to main pole
(c) either of the above depending on voltage
(d) either of the above depending on power factor

Ans: a

23. The speed of a universal motor is generally reduced by using
(a) gear trains
(b) V-belts
(c) brakes
(d) chains

Ans: a

24. When a D.C. series motor is connected to A.C. supply, the power factor will be low because of
(a) high inductance of field and armature circuits
(b) induced current in rotor due to variations of flux
(c) fine copper wire winding
(d) none of the above

Ans: a

25. In a hysteresis motor, the rotor must have
(a) retentivity
(b) resistivity
(c) susceptibility
(d) none of the above

Ans: a

26. The rotor of a hysteresis motor is made of
(a) aluminium
(b) cast iron
(c) chrome steel
(d) copper

Ans: c

27. The electric motor used in portable drills is
(a) capacitor run motor
(b) hysteresis motor
(c) universal motor
(d) repulsion motor

Ans: c

28. Which of the following applications always have some load whenever switched on ?
(a) Vacuum cleaners
(b) Fan motors
(c) Pistol drills
(d) All of the above

Ans: c

29. In repulsion motor, maximum torque is developed when
(a) brush axis is at 45° electrical to the field axis
(b) brush axis coincides with the field axis
(c) brush axis is at 90° electrical to the field axis
(d) none of the above

Ans: a

30. Speed torque characteristic of a repulsion induction motor is similar to that of a D.C.
(a) shunt motor
(b) series motor
(c) compound motor
(d) separately excited motor

Ans: c

31. The shaded pole motor is used for
(a) high starting torque
(b) low starting torque
(c) medium starting torque
(d) very high starting torque

Ans: b

32. The motor used for the compressors is
(a) d.c. series motor
(c) capacitor-start capacitor-run motor
(d) reluctance motor

Ans: c

33. Which of the following motors is used in a situation where load increases with speed ?
(a) Induction motor
(b) Three-phase series motor
(c) Schrage motor
(d) Hysteresis motor

Ans: b

34. In repulsion motor, zero torque is developed when
(a) brush axis is 45° electrical to field axis
(b) brush axis coincides with the field axis
(c) brush axis is 90° electrical to field axis
(d) both (b) and (c)

Ans: d

35. If a single phase induction motor runs slower than normal, the most likely defect is
(a) worn bearings
(b) short-circuit in the winding
(c) open-circuit in the winding
(d) none of the above

Ans: a

36. Which of the following motors is used in tape-recorders ?
(a) Hysteresis motor
(b) Reluctance motor
(c) Capacitor-run motor
(d) Universal motor

Ans: a

37. In a universal motor, the most common cause of brush sparking is
(a) open armature winding
(b) shorted armature winding
(c) shorted field winding
(d) high commutator mica
(e) all of the above

Ans: e

38. Most of the fractional horsepower motors have either
(a) hard and annealed bearings
(b) ball or roller bearings
(c) soft and porous bearings
(d) plain or sleeve bearings

Ans: d

39. Which of the following motors has two separate windings on the motor ?
(a) Repulsion motor
(b) Repulsion induction motor
(c) Repulsion start induction run motor
(d) None of the above

Ans: b

40. A shaded pole motor does not possess
(a) centrifugal switch
(b) capacitor
(c) commutator
(d) all of the above

Ans: d

41. In a A.C. series motor armature coils are usually connected to commutator
(a) through resistance
(b) through reactances
(c) through capacitors
(d) solidly

Ans: a

42. A repulsion motor is equipped with
(a) slip rings
(b) commutator
(c) both (a) and (b)
(d) none of the above

Ans: b

43. Locked rotor current of a shaded pole motor is
(a) equal to full load current
(b) less than full load current
(c) slightly more than full load current
(d) several times the full load current

Ans: c

44. Which of the following statements regarding hysteresis motor is in incorrect ?
(a) It is extremely sensitive to fluctuations in supply voltage
(b) Its high starting torque is due to its high rotor hysteresis loss
(c) It is extremely quiet in operation
(d) It accelerates from rest to full-speed almost instantaneously

Ans: a

45. The starting winding of a single-phase motor is placed in
(a) armature
(b) field
(c) rotor
(d) stator

Ans: d

Tags -
#MCQ on electrical engineering
#Single Phase Motors mcq
#Electrical Multiple Choice Questions
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