1.Which of the following motors uses a commutator
a) universal motor
b) split phase motor
c) shaded pole motor
d) none of the above
ans. a
2. If a dc series motor is connected to an ac supply
a) the motor will not start
b) the motor will start but then come to stop
c) the motor will start and run but will have poor performance
d) None of these
ans. c
3. If a 3-phase , 4-pole, 50 Hz induction motor runs at a speed of 1440 rpm then the slip is
a) 0.03
b) 0.10
c) 0.04
d) 0.05
ans. c
4. A starting torque of 100 Nm is developed by an auto-transformer starter with a tapping of 40%. If the tapping of auto transformer starter is at 80% , then the starting torque would be
a) 200 Nm
b) 50 Nm
c) 400 Nm
d) 25 Nm
ans. c
5. The complete circle diagram of a 3-phase induction motor can be drawn with the help of
a) running light test alone
b) both running light and blocked rotor tests
c) running light , blocked rotor and stator resistance tests
d) blocked rotor test alone
ans. c
6. The power factor of a delta connected 3-phase , 50 Kw induction motor is 0.4 when delivering 20 % of its rated load. If its stator is reconnected in star , then its pf
a) remains unchanged
b) is improved
c) is worsened
d) none of these
ans. b
7. A 3-phase induction motor runs at 980 rpm at no load. If its squirrel cage rotor is replaced by solid cylinder, then its no load speed would be
a) zero
b) 980 rpm
c) below 980 rpm
d) 490 rpm
ans. c
8. An induction motor in which the stator has the squirrel cage winding is
a) 3-phase squirrel cage motor
b) 1-phase induction motor
c) 1-phase ceiling fan
d) 1-phase table fan
ans. c
9. For satisfactory performance of a 3-phase 420 V , 60 Hz induction motor , the supply voltage at 50 Hz should be equal to
a) 420 V
b) 380 V
c) 350 V
d) 400 V
ans. c
10. A 3-phase wound rotor induction motor with star-connected rotor, runs clockwise. If the phase sequence of the rotor terminals is changed, then the motor would
a) not run
b) run clockwise
c) run anti -clockwise
d) none of these
ans. b
a) universal motor
b) split phase motor
c) shaded pole motor
d) none of the above
ans. a
2. If a dc series motor is connected to an ac supply
a) the motor will not start
b) the motor will start but then come to stop
c) the motor will start and run but will have poor performance
d) None of these
ans. c
3. If a 3-phase , 4-pole, 50 Hz induction motor runs at a speed of 1440 rpm then the slip is
a) 0.03
b) 0.10
c) 0.04
d) 0.05
ans. c
4. A starting torque of 100 Nm is developed by an auto-transformer starter with a tapping of 40%. If the tapping of auto transformer starter is at 80% , then the starting torque would be
a) 200 Nm
b) 50 Nm
c) 400 Nm
d) 25 Nm
ans. c
5. The complete circle diagram of a 3-phase induction motor can be drawn with the help of
a) running light test alone
b) both running light and blocked rotor tests
c) running light , blocked rotor and stator resistance tests
d) blocked rotor test alone
ans. c
6. The power factor of a delta connected 3-phase , 50 Kw induction motor is 0.4 when delivering 20 % of its rated load. If its stator is reconnected in star , then its pf
a) remains unchanged
b) is improved
c) is worsened
d) none of these
ans. b
7. A 3-phase induction motor runs at 980 rpm at no load. If its squirrel cage rotor is replaced by solid cylinder, then its no load speed would be
a) zero
b) 980 rpm
c) below 980 rpm
d) 490 rpm
ans. c
8. An induction motor in which the stator has the squirrel cage winding is
a) 3-phase squirrel cage motor
b) 1-phase induction motor
c) 1-phase ceiling fan
d) 1-phase table fan
ans. c
9. For satisfactory performance of a 3-phase 420 V , 60 Hz induction motor , the supply voltage at 50 Hz should be equal to
a) 420 V
b) 380 V
c) 350 V
d) 400 V
ans. c
10. A 3-phase wound rotor induction motor with star-connected rotor, runs clockwise. If the phase sequence of the rotor terminals is changed, then the motor would
a) not run
b) run clockwise
c) run anti -clockwise
d) none of these
ans. b
