1. In which of the following motors, external resistance can be added to start the motor?
a) a squirrel cage induction motor
b) a slip ring induction motor
c) a wound synchronous motor
d) a salient pole synchronous motor
ans. b
2. which of the following lubricants is the shaft of the motor lubricated?
a) Graphite
b) Grease
c) Silicon oil
d) Mineral oil
ans. b
3. An induction motor has a rated speed of 715 rpm. How many poles has its rotating magnetic field?
a) 2 poles
b) 4 poles
c) 6 poles
d) none of these
ans. d
4. The rated speed of an induction motor is 1410 rpm. What is meant by the statement " the slip s=1"?
a) The speed of the motor is higher than the synchronous speed
b) The motor runs at a synchronous speed
c) The motor runs at its rated speed
d) The rotor is stationary
ans. d
5. The injected emf in the rotor of an induction motor must have
a) the same frequency as the slip frequency
b) the same phase as the motor emf
c) a high value for satisfactory speed control
d) none of these
ans. a
6. The field of an induction motor rotor rotates with reference to stator at
a) synchronous speed
b) slip speed
c) rotor speed
d) very low speed
ans. a
7. The reactance per phase as compared to the resistance per phase of and induction motor is
a) quite high
b) slightly large
c) almost same
d) very small
ans. a
8. Which of the following is most economical method for starting single-phase motor?
a) Capacitor-start method
b) Split phase method
c) Induction start method
d) Resistance start method
ans. a
9. Which of the following motors is most suitable for signalling devices and timer
a) DC series motor
b) DC shunt motor
c) two phase induction motor
d) reluctance motor
ans. d
10. Which of the following consumers draws inductive reactive power ?
a) an electrical heater
b) a filament lamp
c) an electrolysis system which draws the current via transformers and rectifiers
d) a 3-phase induction motor
ans. d
a) a squirrel cage induction motor
b) a slip ring induction motor
c) a wound synchronous motor
d) a salient pole synchronous motor
ans. b
2. which of the following lubricants is the shaft of the motor lubricated?
a) Graphite
b) Grease
c) Silicon oil
d) Mineral oil
ans. b
3. An induction motor has a rated speed of 715 rpm. How many poles has its rotating magnetic field?
a) 2 poles
b) 4 poles
c) 6 poles
d) none of these
ans. d
4. The rated speed of an induction motor is 1410 rpm. What is meant by the statement " the slip s=1"?
a) The speed of the motor is higher than the synchronous speed
b) The motor runs at a synchronous speed
c) The motor runs at its rated speed
d) The rotor is stationary
ans. d
5. The injected emf in the rotor of an induction motor must have
a) the same frequency as the slip frequency
b) the same phase as the motor emf
c) a high value for satisfactory speed control
d) none of these
ans. a
6. The field of an induction motor rotor rotates with reference to stator at
a) synchronous speed
b) slip speed
c) rotor speed
d) very low speed
ans. a
7. The reactance per phase as compared to the resistance per phase of and induction motor is
a) quite high
b) slightly large
c) almost same
d) very small
ans. a
8. Which of the following is most economical method for starting single-phase motor?
a) Capacitor-start method
b) Split phase method
c) Induction start method
d) Resistance start method
ans. a
9. Which of the following motors is most suitable for signalling devices and timer
a) DC series motor
b) DC shunt motor
c) two phase induction motor
d) reluctance motor
ans. d
10. Which of the following consumers draws inductive reactive power ?
a) an electrical heater
b) a filament lamp
c) an electrolysis system which draws the current via transformers and rectifiers
d) a 3-phase induction motor
ans. d
