Poly Phase Induction Motor mcq objective questions and answers part1

Q1. In a three-phase induction motor power factor at starting is
(A) high as compared to that while running
(B) low as compared to that while running
(C) the same as that while running
(D) None of these

Q2. Insertion of resistance in the stator of an induction motor
(A) increases the load torque
(B) decreases the starting torque
(C) increases the starting torque
(D) none of the above

Q3. The rotor of an induction motor runs at
(A) synchronous speed
(B) below synchronous speed
(C) above synchronous speed
(D) any of the above

Q4. The torque of an induction motor is
(A) directly proportional to slip
(B) inversely proportional to slip
(C) proportional to the square of the slip
(D) none of the above

Q5. A squirrel cage induction motor is not selected when
(A) initial cost is the main consideration
(B) maintenance cost is to be kept low
(C) higher starting torque is the main consideration
(D) all above considerations are involved

Q6. type of induction motor used for driving high inertia loads
(A) slip ring type
(B) squirrel cage type
(C) any of the above
(D) none of the above

Q7. In case of a double cage induction motor, the inner cage has
(A) high inductance arid low resistance
(B) low inductance and high resistance
(C) low inductance and low resistance
(D) high inductance and high resistance

Q8. The torque developed by a 3-phase induction motor least depends on
(A) rotor current
(B) rotor power factor
(C) rotor EMF
(D) shaft diameter

Q9. What will happen if the relative speed between the rotating flux of stator and rotor of the induction motor is zero ?
(A) The slip of the motor will be 1%
(B) The rotor will not run
(C) The rotor will run at very high speed
(D) The torque produced will be very large

Q10. The stating torque of the slip ring induction motor can be increased by adding
(A) external inductance to the rotor
(B) external resistance to the rotor
(C) external capacitance to the rotor
(D) both resistance and inductance to rotor

Q11. In three-phase induction motors sometimes copper bars are placed deep in the rotor to
(A) improve starting torque
(B) reduce copper losses
(C) improve efficiency
(D) improve power factor

Q12. In a three-phase induction motor
(A) iron losses in stator will be negligible as compared to that in rotor
(B) iron losses in motor will be negligible as compared to that in rotor
(C) iron losses in stator will be less than that in rotor
(D) iron losses in stator will be more than that in rotor

Q13. A 3-phase slip ring motor has
(A) double cage rotor
(B) wound rotor
(C) short-circuited rotor
(D) any of the above

Q14. A 3-phase induction motor stator delta connected, is carrying full load and one of its fuses blows out. Then the motor
(A) will continue running burning its one phase
(B) will continue running burning its two phases
(C) will stop and carry heavy current causing permanent damage to its winding
(D) will continue running without any harm to the winding

Q15. In a three-phase induction motor, the number of poles in the rotor winding is always
(A) zero
(B) more than the number of poles in stator
(C) less than number of poles in stator
(D) equal to number of poles in stator

Q16. In three-phase squirrel-cage induction motors rotor conductors
(A) ends are short-circuited through slip rings
(B) are short-circuited through end rings
(C) are kept open
(D) are connected to insulation

Q17. Rotor rheostat control method of speed control is used for
(A) squirrel-cage induction motors only
(B) slip ring induction motors only
(C) Both of these
(D) none of these

Q18. When the equivalent circuit diagram of double squirrel-cage induction motor is constructed the two cages can be considered in
(A) series
(B) parallel
(C) series-parallel
(D) parallel with stator

Q19. The auto-starters (using three auto transformers) can be used to start cage induction motor of the following type
(A) star connected only
(B) delta connected only
(C) Both of these
(D) none of these

Q20. Which of the following methods is easily applicable to control the speed of the squirrel-cage induction motor?
(A) By changing the number of stator poles
(B) Rotor rheostat control
(C) By operating two motors in cascade
(D) By injecting EMF in the rotor circuit