1. Starting winding of a single phase motor of a refrigerator is disconnected from the circuit by means of a
(a) magnetic relay
(b) thermal relay
(c) centrifugal switch
(d) none of the above
Ans: a
2. 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
3. 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
4. Which of the following statements regarding two value capacitor motor is incorrect ?
(a) It is a reversing motor
(b) It is preferred to permanent-split single-value capacitor motor where frequent reversals are required
(c) It has low starting as well as rush¬ing currents
(d) It has high starting torque
Ans: b
5. Two-value capacitor motor finds increased application as compressor motor in small home air-conditioners because
(a) it is comparatively cheaper
(b) it has almost non-destructible capacitor
(c) it has low starting as well as running currents at relatively high power factor
(d) it is quiet in operation
Ans: c
6. If the centrifugal switch of a two-value capacitor motor using two capacitors fails to open then
(a) motor will not come upto speed
(b) motor will not carry the load
(c) current drawn by the motor will be excessively high
(d) electrolytic capacitor will, in all probability, suffer break down
Ans: d
7. 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
8. 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
9. 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
10. 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
11. 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 im-mediately connect it to supply
Ans: a
12. 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
13. 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
14. A shaded pole motor does not possess
(a) centrifugal switch
(b) capacitor
(c) commutator
(d) all of the above
Ans: d
15. 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
16. Which of the following statements regarding a reluctance motor is incorrect ?
(a) It cannot be reversed, ordinarily
(b) It requires no D.C. field excitation for its operation
(c) It is nothing else but a single-phase, salient pole synchronous-induction motor
(d) Its squirrel cage-rotor is of unsym-metrical magnetic construction in order to vary reluctance path bet¬ween stator and rotor
Ans: a
17. A universal motor is one which
(a) can be operated either on D.C. or A.C. supply at approximately the same speed and output
(b) can be marketed internationally
(c) runs at dangerously high speed on no-load
Ans: a
18. A repulsion motor is equipped with
(a) slip rings
(b) commutator
(c) both (a) and (b)
(d) none of the above
Ans: b
19. The capacitors used in single-phase capacitor motors have no
(a) voltage rating
(b) dielectric medium
(c) polarity marking
(d) definite value
Ans: c
20. 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
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