Single Phase Induction Motors Multiple Choice Questions and Answers In English -05

1. Which motor is normally free from mechanical and magnetic vibrations ?

(A) Split phase motor
(B) Universal motor
(C) Hysteresis motor
(D) Shaded pole motor
Ans: C

2. 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

3. 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

4. If starting winding of a single-phase induction motor is left in the circuit, it will
(A) run faster
(B) spark at light loads
(C) draw excessive current and overheat
(D) run slower
Ans: C

5. 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

6. Which of the following statements regarding reluctance-start motor is incorrect ?
(A) It is similar to reluctance motor
(B) It is basically an induction motor and not a synchronous one
(C) So far as its basic working principle is concerned, it is similar to shaded pole motor
(D) the air-gap between rotor and salient poles is non- uniform
Ans: A

7. To reverse the direction of rotation of acapacitor start motor while it is running we should
(A) disconnect motor from the supply till it stops then reconnect it to supply with reversed connection of main or auxiliary winding
(B) disconnect motor from supply and immediately reconnect it to supply with reversed connections of the main winding
(C) reverse the direction of connection of the auxiliary winding and after motor comes to rest then connect auxiliary winding to the supply
(D) reverse the direction of connections of the auxiliary winding and immediately connect it to supply
Ans: A

8. In case of a reluctance motor, when the load is increased so that it cannot maintain synchronous speed the motor will
(A) become unstable
(B) draw excessive armature current and may burn out
(C) fall out of synchronism and come to stand still
(D) run as induction motor
Ans: D

9. If a D.C. series motor is operated on A.C. supply, it will
(A) spark excessively
(B) have poor efficiency
(C) have poor power factor
(D) all of the above
Ans: D

10. A reluctance motor
(A) is self-starting
(B) is constant speed motor
(C) needs no D.C. excitation
(D) all of the above
Ans: D

11. As hysteresis motors are free from mechanical and magnetic vibrations therefore these are considered as suitable for
(A) fans
(B) blowers
(C) sound equipment
(D) mixer grinders
Ans: C

12. In a hysteresis motor, the rotor must have
(A) retentivity
(B) resistivity
(C) susceptibility
(D) none of the above
Ans: A

13. The rotor of a hysteresis motor is made of
(A) aluminium
(B) cast iron
(C) chrome steel
(D) copper
Ans: C

14. 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

15. The capacitors used in single-phase capacitor motors have no
(A) voltage rating
(B) dielectric medium
(C) polarity marking
(D) definite value
Ans: C

16. The electric motor used in portable drills is
(A) capacitor run motor
(B) hysteresis motor
(C) universal motor
(D) repulsion motor
Ans: C

17. 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

18. The speed control of universal motor used for sewing machines is by
(A) friction
(B) varying the resistance
(C) tapping the field
(D) centrifugal mechanism
Ans: B

19. Torque developed by a single phase induction motor at starting is
(A) pulsating
(B) uniform
(C) none of the above
(D) nil
Ans: D

20. In split phase motor main winding is of
(A) thin wire placed at the top of the slots
(B) thin wire placed at the bottom of the slots
(C) thick wire placed at the bottom of the slots
(D) thick wire placed at the top of the” slots
Ans: C