1. Which of the following motors is used most frequently ?
a) DC shunt motor
b) AC induction motor
c) 3-phase commutator motor
d) 3-phase induction motor
ans. d
2. What is the advantage of the slip ring induction motor over the squirrel cage induction motor?
a) It is suitable for higher speeds
b) Its efficiency is higher
c) Its power factor is higher
d) It can be started with the help of rotor resistances
ans. d
3. The starting torque of the slip ring induction motor can be increased by
a) adding resistance to the rotor
b) adding resistance to the stator
c) adding resistance to both
d) none of these
ans.
4. What will happen to rotor copper losses of the frequency of the input to an induction motor increases?
a) Increases
b) Decreases
c) Remains same
d) None of these
ans. a
5. In an induction motor, if the phase sequence of applied voltage is changed
a) no back emf will be developed in rotor
b) no torque will be developed by rotor
c) speed will drop to zero
d) direction of rotation of motor will change
ans. d
6. If a rotor of induction motor could be theoretically rotated at synchronous speed, the voltage that would be generated in the rotor is
a) zero
b) equal to applied voltage
c) more than applied voltage
d) none of these
ans. a
7. In an induction motor, if the rotor is locked, then the rotor frequency of the induction motor will be
a) more than the supply frequency
b) zero
c) equal to the supply frequency
d) less than the supply frequency
ans. c
8. When measuring the no load input to an induction motor, using two wattmeter method, it is necessary to subtract wattmeter readings , because the no load power factor is
a) lagging
b) less than 0.5
c) unity
d) zero
ans. b
9. The purpose of skewing of rotor slots in induction motor is
a) to reduce the magnetic hum of motor
b) to increase the distribution factor
c) to reduce the locking tendency of rotor
d) to increase the breadth factor
ans. c
10. If the speed is 460 rpm then the number of poles of a 50 Hz induction motor are
a) 4
b) 8
c) 12
d) 18
ans. c
a) DC shunt motor
b) AC induction motor
c) 3-phase commutator motor
d) 3-phase induction motor
ans. d
2. What is the advantage of the slip ring induction motor over the squirrel cage induction motor?
a) It is suitable for higher speeds
b) Its efficiency is higher
c) Its power factor is higher
d) It can be started with the help of rotor resistances
ans. d
3. The starting torque of the slip ring induction motor can be increased by
a) adding resistance to the rotor
b) adding resistance to the stator
c) adding resistance to both
d) none of these
ans.
4. What will happen to rotor copper losses of the frequency of the input to an induction motor increases?
a) Increases
b) Decreases
c) Remains same
d) None of these
ans. a
5. In an induction motor, if the phase sequence of applied voltage is changed
a) no back emf will be developed in rotor
b) no torque will be developed by rotor
c) speed will drop to zero
d) direction of rotation of motor will change
ans. d
6. If a rotor of induction motor could be theoretically rotated at synchronous speed, the voltage that would be generated in the rotor is
a) zero
b) equal to applied voltage
c) more than applied voltage
d) none of these
ans. a
7. In an induction motor, if the rotor is locked, then the rotor frequency of the induction motor will be
a) more than the supply frequency
b) zero
c) equal to the supply frequency
d) less than the supply frequency
ans. c
8. When measuring the no load input to an induction motor, using two wattmeter method, it is necessary to subtract wattmeter readings , because the no load power factor is
a) lagging
b) less than 0.5
c) unity
d) zero
ans. b
9. The purpose of skewing of rotor slots in induction motor is
a) to reduce the magnetic hum of motor
b) to increase the distribution factor
c) to reduce the locking tendency of rotor
d) to increase the breadth factor
ans. c
10. If the speed is 460 rpm then the number of poles of a 50 Hz induction motor are
a) 4
b) 8
c) 12
d) 18
ans. c
