MCQOPTIONS
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MCQOPTIONS
This section includes 165 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
A change of 4% of supply voltage to an induction motor will produce a change of approximately ________? |
| A. | 4% in the rotor torque |
| B. | 8% in the rotor torque |
| C. | 12% in the rotor torque |
| D. | 16% in the rotor torque |
| Answer» E. | |
| 2. |
A 500 kW, 3-phase, 440 volts, 50 Hz, A.C. induction motor has a speed of 960 r.p.m. on full load. The machine has 6 poles. The slip of the machine will be__________? |
| A. | 0.01 |
| B. | 0.02 |
| C. | 0.03 |
| D. | 0.04 |
| Answer» E. | |
| 3. |
A 3-phase slip ring motor has____________? |
| A. | double cage rotor |
| B. | wound rotor |
| C. | short-circuited rotor |
| D. | any of the above |
| Answer» C. short-circuited rotor | |
| 4. |
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 |
| Answer» B. will continue running burning its two phases | |
| 5. |
A 3-phase induction motor delta connected is carrying too heavy 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 phase |
| C. | will stop and carry heavy current causing permanent damage to its winding |
| D. | will continue running without any harm to the winding |
| Answer» D. will continue running without any harm to the winding | |
| 6. |
A 3-phase 440 V, 50 Hz induction motor has 4% slip. The frequency of rotor e.m.f. will be____________? |
| A. | 200 Hz |
| B. | 50 Hz |
| C. | 2 Hz |
| D. | 0.2 Hz |
| Answer» D. 0.2 Hz | |
| 7. |
5 H.P., 50-Hz, 3-phase, 440 V, induction motors are available for the following r.p.m. Which motor will be the costliest ? |
| A. | 730 r.p.m. |
| B. | 960 r.p.m. |
| C. | 1440 r.p.m. |
| D. | 2880 r.p.m. |
| Answer» B. 960 r.p.m. | |
| 8. |
Insertion of resistance in the rotor of an induction motor to develop a given torque |
| A. | ecreases the rotor current |
| B. | ncreases the rotor current |
| C. | otor current becomes zero |
| D. | otor current remains same |
| Answer» E. | |
| 9. |
Which of the following component is usually fabricated out of silicon steel? |
| A. | earings |
| B. | haft |
| C. | tator core |
| D. | one of the above |
| Answer» D. one of the above | |
| 10. |
The speed of a squirrel-cage induction motor can be controlled by all of the following except |
| A. | hanging supply frequency |
| B. | hanging number of poles |
| C. | hanging winding resistance |
| D. | educing supply voltage |
| Answer» D. educing supply voltage | |
| 11. |
Reduced voltage starter can be used with |
| A. | lip ring motor only but not with squirrel cage induction motor |
| B. | quirrel cage induction motor only but not with slip ring motor |
| C. | quirrel cage as well as slip ring induction motor |
| D. | one of the above |
| Answer» D. one of the above | |
| 12. |
In induction motor, percentage slip depends on |
| A. | upply frequency |
| B. | upply voltage |
| C. | opper losses in motor |
| D. | one of the above |
| Answer» D. one of the above | |
| 13. |
The torque developed by a 3-phase induction motor least depends on |
| A. | otor current |
| B. | otor power factor |
| C. | otor e.m.f. |
| D. | haft diameter |
| Answer» E. | |
| 14. |
Slip of an induction motor is negative when |
| A. | agnetic field and rotor rotate in opposite direction |
| B. | otor speed is less than the synchronous speed of the field and are in the same direction |
| C. | otor speed is more than the synchronous speed of the field and are in the same direction |
| D. | one of the above |
| Answer» D. one of the above | |
| 15. |
If any two phases for an induction motor are interchanged |
| A. | he motor will run in reverse direction |
| B. | he motor will run at reduced speed |
| C. | he motor will not run |
| D. | he motor will burn |
| Answer» B. he motor will run at reduced speed | |
| 16. |
The efficiency of an induction motor can be expected to be nearly |
| A. | 0 to 90 % |
| B. | 0 to 90 % |
| C. | 5 to 98 % |
| D. | 9 % |
| Answer» C. 5 to 98 % | |
| 17. |
The torque developed in the cage induction motor with auto-starter is |
| A. | /torque with direct switching |
| B. | × torque with direct switching |
| C. | 2 × torque with direct switching |
| D. | 2/torque with direct switching |
| Answer» D. 2/torque with direct switching | |
| 18. |
The frame of an induction motor is usually made of |
| A. | ilicon steel |
| B. | ast iron |
| C. | luminium |
| D. | ronze |
| Answer» C. luminium | |
| 19. |
As load on an induction motor goes on increasing |
| A. | ts power factor goes on decreasing |
| B. | ts power factor remains constant |
| C. | ts power factor goes on increasing even after full load |
| D. | ts power factor goes on increasing up to full load and then it falls again |
| Answer» E. | |
| 20. |
Less maintenance troubles are experienced in case of |
| A. | lip ring induction motor |
| B. | quirrel cage induction motor |
| C. | oth (A) and (B) |
| D. | one of the above |
| Answer» C. oth (A) and (B) | |
| 21. |
An induction motor with 1000 r.p.m. speed will have |
| A. | poles |
| B. | poles |
| C. | poles |
| D. | poles |
| Answer» C. poles | |
| 22. |
The number of slip rings on a squirrel cage induction motor is usually |
| A. | wo |
| B. | hree |
| C. | our |
| D. | one |
| Answer» E. | |
| 23. |
The shaft of an induction motor is made of |
| A. | igh speed steel |
| B. | tainless steel |
| C. | arbon steel |
| D. | ast iron |
| Answer» D. ast iron | |
| 24. |
The maximum torque in an induction motor depends on |
| A. | requency |
| B. | otor inductive reactance |
| C. | quare of supply voltage |
| D. | ll of the above |
| Answer» E. | |
| 25. |
In an induction motor, no-load the slip is generally |
| A. | ess than 1 % |
| B. | .5 % |
| C. | % |
| D. | % |
| Answer» B. .5 % | |
| 26. |
Size of a high speed motor as compared to low speed motor for the same H.P. will be |
| A. | igger |
| B. | maller |
| C. | ame |
| D. | ny of the above |
| Answer» C. ame | |
| 27. |
In a squirrel cage motor the induced e.m.f. is |
| A. | ependent on the shaft loading |
| B. | ependent on the number of slots |
| C. | lip times the stand still e.m.f. induced in the rotor |
| D. | one of the above |
| Answer» D. one of the above | |
| 28. |
In squirrel cage induction motors, the rotor slots are usually given slight skew in order to |
| A. | educe windage losses |
| B. | educe eddy currents |
| C. | educe accumulation of dirt and dust |
| D. | educe magnetic hum |
| Answer» E. | |
| 29. |
The auto-starters (using three auto transformers) can be used to start cage induction motor of the following type |
| A. | tar connected only |
| B. | elta connected only |
| C. | oth (A) and (B) |
| D. | one of the above |
| Answer» D. one of the above | |
| 30. |
The shape of the torque/slip curve of induction motor is |
| A. | arabola |
| B. | yperbola |
| C. | ectangular parabola |
| D. | traight line |
| Answer» D. traight line | |
| 31. |
When the equivalent circuit diagram of double squirrel-cage induction motor is constructed the two cages can be considered |
| A. | n series |
| B. | n parallel |
| C. | n series-parallel |
| D. | n parallel with stator |
| Answer» C. n series-parallel | |
| 32. |
The starting torque of a 3 phase squirrel cage induction motor is |
| A. | wice the full load torque |
| B. | .5 times the full load torque |
| C. | qual to full load torque |
| D. | ny of the above |
| Answer» C. qual to full load torque | |
| 33. |
Step-less speed control of induction motor is possible by which of the following methods? |
| A. | .m.f. injection in rotor eueuit |
| B. | hanging the number of poles |
| C. | ascade operation |
| D. | one of the above |
| Answer» C. ascade operation | |
| 34. |
What will happen if the relative speed between the rotating flux of stator and rotor of the induction motor is zero? |
| A. | he slip of the motor will be 5% |
| B. | he rotor will not run |
| C. | he rotor will run at very high speed |
| D. | he torque produced will be very large |
| Answer» C. he rotor will run at very high speed | |
| 35. |
The torque of a rotor in an induction motor under running condition is maximum |
| A. | t the unit value of slip |
| B. | t the zero value of slip |
| C. | t the value of the slip which makes rotor reactance per phase equal to the resistance per phase |
| D. | t the value of the slip which makes the rotor reactance half of the rotor |
| Answer» D. t the value of the slip which makes the rotor reactance half of the rotor | |
| 36. |
Short-circuit test on an induction motor cannot be used to determine |
| A. | indage losses |
| B. | opper losses |
| C. | ransformation ratio |
| D. | ower scale of circle diagram |
| Answer» B. opper losses | |
| 37. |
In an induction motor if air-gap is increased |
| A. | he power factor will be low |
| B. | indage losses will be more |
| C. | earing friction will reduce |
| D. | opper loss will reduce in an induction motor |
| Answer» B. indage losses will be more | |
| 38. |
In three-phase squirrel-cage induction motors |
| A. | otor conductor ends are short-circuited through slip rings |
| B. | otor conductors are short-circuited through end rings |
| C. | otor conductors are kept open |
| D. | otor conductors are connected to insulation |
| Answer» C. otor conductors are kept open | |
| 39. |
Which of the following methods is easily applicable to control the speed of the squirrel-cage induction motor? |
| A. | y changing the number of stator poles |
| B. | otor rheostat control |
| C. | y operating two motors in cascade |
| D. | y injecting e.m.f. in the rotor circuit |
| Answer» B. otor rheostat control | |
| 40. |
Low voltage at motor terminals is due to |
| A. | nadequate motor wiring |
| B. | oorly regulated power supply |
| C. | ny one of the above |
| D. | one of the above |
| Answer» D. one of the above | |
| 41. |
A 3-phase slip ring motor has |
| A. | ouble cage rotor |
| B. | ound rotor |
| C. | hort-circuited rotor |
| D. | ny of the above |
| Answer» C. hort-circuited rotor | |
| 42. |
In an induction motor the relationship between stator slots and rotor slots is that |
| A. | tator slots are equal to rotor slots |
| B. | tator slots are exact multiple of rotor slots |
| C. | tator slots are not exact multiple of rotor slots |
| D. | one of the above |
| Answer» D. one of the above | |
| 43. |
A 3-phase induction motor stator delta connected, is carrying full load and one of its fuses blows out. Then the motor |
| A. | ill continue running burning its one phase |
| B. | ill continue running burning its two phases |
| C. | ill stop and carry heavy current causing permanent damage to its winding |
| D. | ill continue running without any harm to the winding |
| Answer» B. ill continue running burning its two phases | |
| 44. |
Blocked rotor test on induction motors is used to find out |
| A. | eakage reactance |
| B. | ower factor on short circuit |
| C. | hort-circuit current under rated voltage |
| D. | ll of the above |
| Answer» E. | |
| 45. |
In medium sized induction motors, the slip is generally around |
| A. | .04 % |
| B. | .4 % |
| C. | % |
| D. | 4 % |
| Answer» D. 4 % | |
| 46. |
An induction motor is identical to |
| A. | .C. compound motor |
| B. | .C. series motor |
| C. | ynchronous motor |
| D. | synchronous motor |
| Answer» E. | |
| 47. |
The vafcie of transformation ratio of an induction motor can be found by |
| A. | pen-circuit test only |
| B. | hort-circuit test only |
| C. | tator resistance test |
| D. | one of the above |
| Answer» C. tator resistance test | |
| 48. |
Which type of bearing is provided in small induction motors to support the rotor shaft? |
| A. | all bearings |
| B. | ast iron bearings |
| C. | ush bearings |
| D. | one of the above |
| Answer» B. ast iron bearings | |
| 49. |
If an induction motor with certain ratio of rotor to stator slots, runs at 1/7 of the normal speed, the phenomenon will be termed as |
| A. | umming |
| B. | unting |
| C. | rawling |
| D. | ogging |
| Answer» D. ogging | |
| 50. |
A change of 4% of supply voltage to an induction motor will produce a change of approximately |
| A. | % in the rotor torque |
| B. | % in the rotor torque |
| C. | 2% in the rotor torque |
| D. | 6% in the rotor torque |
| Answer» E. | |