MCQOPTIONS
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MCQOPTIONS
This section includes 29 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Machines knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
For a constant load torque, the supply voltage of a squirrel cage induction motor is reduced by a factor of 0.5, its rotor current is modified by a factor is? |
| A. | 2 |
| B. | 0.5 |
| C. | 4 |
| D. | 0.25 |
| Answer» B. 0.5 | |
| 2. |
If a 400 V, 50 hz star connected, 3-phase squirrel cage induction motor is operated from 400V and 75 Hz supply. The torque that the motor can now provide while drawing rated current from the supply will _________ |
| A. | reduce |
| B. | increase |
| C. | remains same |
| D. | increases or reduces based on the rotor resistance. |
| Answer» B. increase | |
| 3. |
The torque developed in the three phase induction motor depends on _________ |
| A. | (i) only |
| B. | (ii) only |
| C. | both (i) and (ii) |
| D. | none of the mentionedView Answer |
| Answer» D. none of the mentionedView Answer | |
| 4. |
A three phase induction motor is connected to 400V, 50 hz supply. If the stator to rotor turn ratio is 2, the standstill rotor induced voltage per phase is? |
| A. | 115.5 V |
| B. | 231 V |
| C. | 346 V |
| D. | 200 V |
| Answer» B. 231 V | |
| 5. |
In a three phase induction motor, voltage between the slip rings at standstill is 50 V. At full load the slip is 0.04. The voltage between slip rings at full load is? |
| A. | 2V |
| B. | 50V |
| C. | 20V |
| D. | 5V |
| Answer» B. 50V | |
| 6. |
A 3-phase induction motor is operating at slip ‘s’. If the slip is reversed, its slip at the instant will be _________ |
| A. | 2-s |
| B. | zero |
| C. | 2+s |
| D. | 1-s |
| Answer» B. zero | |
| 7. |
In an induction motor slip will be negative when the _________ |
| A. | rotor rotates at speed more than synchronous speed and in the direction of the rotation of stator field |
| B. | stator magnetic field and rotor rotate in opposite direction |
| C. | rotor rotates at speed less than synchronous speed and in the opposite direction of the rotation of stator field |
| D. | rotor rotates at speed more than synchronous speed and in the opposite direction of the rotation of stator field |
| Answer» B. stator magnetic field and rotor rotate in opposite direction | |
| 8. |
The mmf produced by the current of the three phase induction motor _________ |
| A. | is standstill with respect to stator mmf |
| B. | rotates at the speed of rotor in air gap |
| C. | rotates at slip speed with respect to stator mmf |
| D. | rotates at synchronous speed with respect to rotor |
| Answer» B. rotates at the speed of rotor in air gap | |
| 9. |
If the three phase supply is fed to the stator and it is running at its normal operating conditions. Then the synchronous speed can be defined as speed at which?a) stator magnetic field rotatesb) rotor magnetic field rotatesc) rotor rotatesd) flux is set up in the rotor 7.If the three phase supply is fed to the rotor and it is running at its normal operating conditions. Then the synchronous speed can be defined as speed at which? |
| A. | stator magnetic field rotatesb) rotor magnetic field rotatesc) rotor rotatesd) flux is set up in the rotor 7.If the three phase supply is fed to the rotor and it is running at its normal operating conditions. Then the synchronous speed can be defined as speed at which?a) stator magnetic field rotates |
| B. | rotor magnetic field rotatesc) rotor rotatesd) flux is set up in the rotor 7.If the three phase supply is fed to the rotor and it is running at its normal operating conditions. Then the synchronous speed can be defined as speed at which?a) stator magnetic field rotatesb) rotor magnetic field rotates |
| C. | rotor rotatesd) flux is set up in the rotor 7.If the three phase supply is fed to the rotor and it is running at its normal operating conditions. Then the synchronous speed can be defined as speed at which?a) stator magnetic field rotatesb) rotor magnetic field rotatesc) rotor rotates |
| D. | flux is set up in the rotor 7.If the three phase supply is fed to the rotor and it is running at its normal operating conditions. Then the synchronous speed can be defined as speed at which?a) stator magnetic field rotatesb) rotor magnetic field rotatesc) rotor rotatesd) flux is set up in the rotorView Answer |
| Answer» B. rotor magnetic field rotatesc) rotor rotatesd) flux is set up in the rotor 7.If the three phase supply is fed to the rotor and it is running at its normal operating conditions. Then the synchronous speed can be defined as speed at which?a) stator magnetic field rotatesb) rotor magnetic field rotates | |
| 10. |
The voltage actually used to set up the working flux in the three phase induction motor is _________ |
| A. | equal to applied voltage |
| B. | less than applied voltage |
| C. | more than applied voltage |
| D. | equal to rotor induced emf. |
| Answer» B. less than applied voltage | |
| 11. |
The rotor of the induction motor must never run at synchronous speed because then the relative speed between the rotating flux and rotor will be _________ |
| A. | zero and hence torque will be zero |
| B. | zero, and torque will be maximum |
| C. | maximum and hence, torque will be zero |
| D. | maximum, and torque will also be zero |
| Answer» B. zero, and torque will be maximum | |
| 12. |
Two of the supply terminals to a three phase induction motor gets interchanges while regular scheduling work. When the machine is switched on, then it will _________ |
| A. | rotate in opposite direction |
| B. | rotate in same direction |
| C. | not start |
| D. | get heated and winding will burn |
| Answer» B. rotate in same direction | |
| 13. |
In an induction motor, when the number of stator slots is equal to an integral multiple of rotor slots? |
| A. | machine will fail to start |
| B. | machine will get heated |
| C. | high starting torque will be achieved |
| D. | discontinuity in torque slip characteristic |
| Answer» B. machine will get heated | |
| 14. |
Rotor leakage reactance for a three phase slip ring induction motor with slip ‘s’ is? |
| A. | s(x2) |
| B. | (x2)/s |
| C. | x2 |
| D. | (x2)(s2) |
| Answer» B. (x2)/s | |
| 15. |
IN_AN_INDUCTION_MOTOR_SLIP_WILL_BE_NEGATIVE_WHEN?$ |
| A. | rotor rotates at speed more than synchronous speed and in the direction of the rotation of stator field |
| B. | stator magnetic field and rotor rotate in opposite direction |
| C. | rotor rotates at speed less than synchronous speed and in the opposite direction of the rotation of stator field |
| D. | rotor rotates at speed more than synchronous speed and in the opposite direction of the rotation of stator field |
| Answer» B. stator magnetic field and rotor rotate in opposite direction | |
| 16. |
In a three phase induction motor, voltage between the slip rings at standstill is 50 V. At full load the slip is 0.04. The voltage between slip rings at full load is$ |
| A. | 2V |
| B. | 50V |
| C. | 20V |
| D. | 5V |
| Answer» B. 50V | |
| 17. |
A_3-phase_induction_motor_is_operating_at_slip_‘s’._If_the_slip_is_reversed,_its_slip_at_the_instant_will_be$# |
| A. | 2-s |
| B. | zero |
| C. | 2+s |
| D. | 1-s |
| Answer» B. zero | |
| 18. |
For a constant load torque, the supply voltage of a squirrel cage induction motor is reduced by a factor of 0.5, its rotor current is modified by a factor |
| A. | 2 |
| B. | 0.5 |
| C. | 4 |
| D. | 0.25 |
| Answer» B. 0.5 | |
| 19. |
If a 400 V, 50 hz star connected, 3-phase squirrel cage induction motor is operated from 400V and 75 Hz supply. The torque that the motor can now provide while drawing rated current from the supply will |
| A. | reduce |
| B. | increase |
| C. | remains same |
| D. | increases or reduces based on the rotor resistance. |
| Answer» B. increase | |
| 20. |
The torque developed in the three phase induction motor depends on |
| A. | standstill rotor phase emf |
| B. | rotor power factor |
| C. | (i) only |
| D. | (ii) only |
| Answer» D. (ii) only | |
| 21. |
A_three_phase_induction_motor_is_connected_to_400V,_50_hz_supply._If_the_stator_to_rotor_turn_ratio_is_2,_the_standstill_rotor_induced_voltage_per_phase_is |
| A. | 115.5 V |
| B. | 231 V |
| C. | 346 V |
| D. | 200 V |
| Answer» B. 231 V | |
| 22. |
The mmf produced by the current of the three phase induction moto? |
| A. | is standstill with respect to stator mmf |
| B. | rotates at the speed of rotor in air gap |
| C. | rotates at slip speed with respect to stator mmf |
| D. | rotates at synchronous speed with respect to rotor |
| Answer» B. rotates at the speed of rotor in air gap | |
| 23. |
If the three phase supply is fed to the rotor and it is running at its normal operating conditions. Then the synchronous speed can be defined as speed at which |
| A. | stator magnetic field rotates |
| B. | rotor magnetic field rotates |
| C. | rotor rotates |
| D. | flux is set up in the rotor |
| Answer» C. rotor rotates | |
| 24. |
If the three phase supply is fed to the stator and it is running at its normal operating conditions. Then the synchronous speed can be defined as speed at which |
| A. | stator magnetic field rotates |
| B. | rotor magnetic field rotates |
| C. | rotor rotates |
| D. | flux is set up in the rotor |
| Answer» B. rotor magnetic field rotates | |
| 25. |
The voltage actually used to set up the working flux in the three phase induction motor is |
| A. | equal to applied voltage |
| B. | less than applied voltage |
| C. | more than applied voltage |
| D. | equal to rotor induced emf. |
| Answer» B. less than applied voltage | |
| 26. |
The rotor of the induction motor must never run at synchronous speed because then the relative speed between the rotating flux and rotor will be |
| A. | zero and hence torque will be zero |
| B. | zero, and torque will be maximum |
| C. | maximum and hence, torque will be zero |
| D. | maximum, and torque will also be zero |
| Answer» B. zero, and torque will be maximum | |
| 27. |
Two of the supply terminals to a three phase induction motor gets interchanges while regular scheduling work. When the machine is switched on, then it will |
| A. | rotate in opposite direction |
| B. | rotate in same direction |
| C. | not start |
| D. | get heated and winding will burn |
| Answer» B. rotate in same direction | |
| 28. |
In an induction motor, when the number of stator slots is equal to an integral multiple of rotor slots |
| A. | machine will fail to start |
| B. | machine will get heated |
| C. | high starting torque will be achieved |
| D. | discontinuity in torque slip characteristic |
| Answer» B. machine will get heated | |
| 29. |
Rotor leakage reactance for a three phase slip ring induction motor with slip ‘s’ is |
| A. | s(x2) |
| B. | (x2)/s |
| C. | x2 |
| D. | (x2)(s<sup>2</sup>) |
| Answer» B. (x2)/s | |