MCQOPTIONS
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MCQOPTIONS
This section includes 101 Mcqs, each offering curated multiple-choice questions to sharpen your Electrical Engineering Questions knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Slip rings are usually made of___________? |
| A. | copper |
| B. | carbon |
| C. | phospor bronze |
| D. | aluminium |
| Answer» D. aluminium | |
| 2. |
The crawling in the induction motor is caused by____________? |
| A. | low voltage supply |
| B. | high loads |
| C. | harmonics develped in the motor |
| D. | improper design of the machine |
| E. | none of the above |
| Answer» D. improper design of the machine | |
| 3. |
For driving high inertia loads best type of induction motor suggested is_____________? |
| A. | slip ring type |
| B. | squirrel cage type |
| C. | any of the above |
| D. | none of the above |
| Answer» B. squirrel cage type | |
| 4. |
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 |
| Answer» D. all above considerations are involved | |
| 5. |
Short-circuit test on an induction motor cannot be used to determine___________? |
| A. | windage losses |
| B. | copper losses |
| C. | transformation ratio |
| D. | power scale of circle diagram |
| Answer» B. copper losses | |
| 6. |
The term ‘cogging’ is associated with___________? |
| A. | three phase transformers |
| B. | compound generators |
| C. | D.C. series motors |
| D. | induction motors |
| Answer» E. | |
| 7. |
The number of slip rings on a squirrel cage induction motor is usually____________? |
| A. | two |
| B. | three |
| C. | four |
| D. | none |
| Answer» E. | |
| 8. |
An induction motor with 1000 r.p.m. speed will have____________? |
| A. | 8 poles |
| B. | 6 poles |
| C. | 4 poles |
| D. | 2 poles |
| Answer» C. 4 poles | |
| 9. |
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 |
| Answer» C. increases the starting torque | |
| 10. |
The starting torque of a three phase induction motor can be increased by__________? |
| A. | increasing slip |
| B. | increasing current |
| C. | both A. and (b) |
| D. | none of the above |
| Answer» D. none of the above | |
| 11. |
In a star-delta starter of an induction motor___________? |
| A. | resistance is inserted in the stator |
| B. | reduced voltage is applied to the stator |
| C. | resistance is inserted in the rotor |
| D. | applied voltage perl stator phase is 57.7% of the line voltage |
| Answer» E. | |
| 12. |
Reduced voltage starter can be used with_____________? |
| A. | slip ring motor only but not with squirrel cage induction motor |
| B. | squirrel cage induction motor only but not with slip ring motor |
| C. | squirrel cage as well as slip ring induction motor |
| D. | none of the above |
| Answer» D. none of the above | |
| 13. |
The rotor of an induction motor runs at__________? |
| A. | synchronous speed |
| B. | below synchronous speed |
| C. | above synchronous speed |
| D. | any of the above |
| Answer» C. above synchronous speed | |
| 14. |
Which of the following component is usually fabricated out of silicon steel ? |
| A. | Bearings |
| B. | Shaft |
| C. | Statorcore |
| D. | None of the above |
| Answer» D. None of the above | |
| 15. |
Slip ring motor is preferred over squirrel cage induction motor where___________? |
| A. | high starting torque is required |
| B. | load torque is heavy |
| C. | heavy pull out torque is required |
| D. | all of the above |
| Answer» B. load torque is heavy | |
| 16. |
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 | |
| 17. |
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. | |
| 18. |
The starting torque of a 3-phase squirrel cage induction motor is____________? |
| A. | twice the full load torque |
| B. | 1.5 times the full load torque |
| C. | equal to full load torque |
| Answer» C. equal to full load torque | |
| 19. |
The torque of a rotor in an induction motor under running condition is maximum__________? |
| A. | at the unit value of slip |
| B. | at the zero value of slip |
| C. | at the value of the slip which makes rotor reactance per phase equal to the resistance per phase |
| D. | at the value of the slip which makes the rotor reactance half of the rotor |
| Answer» D. at the value of the slip which makes the rotor reactance half of the rotor | |
| 20. |
A pump induction motor is switched on to a supply 30% lower than its rated voltage. The pump runs. What will eventually happen ? It will____________? |
| A. | stall after sometime |
| B. | stall immediately |
| C. | continue to run at lower speed without damage |
| D. | get heated and subsequently get damaged |
| Answer» E. | |
| 21. |
Blocked rotor test on induction motors is used to find out? |
| A. | leakage reactance |
| B. | power factor on short circuit |
| C. | short-circuit current under rated voltage |
| D. | all of the above |
| Answer» E. | |
| 22. |
Insertion of reactance in the rotor circuit_______? |
| A. | reduces starting torque as well as maximum torque |
| B. | increases starting torque as well as maximum torque |
| C. | increases starting torque but maxi-mum torque remains unchanged |
| D. | increases starting torque but maxi-mum torque decreases |
| Answer» B. increases starting torque as well as maximum torque | |
| 23. |
Which motor is preferred for use in mines where explosive gases exist ? |
| A. | Air motor |
| B. | Induction motor |
| C. | D.C. shunt motor |
| D. | Synchronous motor |
| Answer» B. Induction motor | |
| 24. |
Which type of bearing is provided in small induction motors to support the rotor shaft ? |
| A. | Ball bearings |
| B. | Cast iron bearings |
| C. | Bush bearings |
| D. | None of the above |
| Answer» B. Cast iron bearings | |
| 25. |
The speed characteristics of an induction motor closely resemble the speedload characteristics of which of the following machines? |
| A. | D.C. series motor |
| B. | D.C. shunt motor |
| C. | universal motor |
| D. | none of the above |
| Answer» C. universal motor | |
| 26. |
The complete circle diagram of induetion motor can be drawn with the help of data found from__________? |
| A. | noload test |
| B. | blocked rotor test |
| C. | stator resistance test |
| D. | all of the above |
| Answer» E. | |
| 27. |
The circle diagram for an induction motor cannot be used to determine____________? |
| A. | efficiency |
| B. | power factor |
| C. | frequency |
| D. | output |
| Answer» B. power factor | |
| 28. |
The torque developed by a 3-phase induction motor least depends on__________? |
| A. | rotor current |
| B. | rotor power factor |
| C. | rotor e.m.f. |
| D. | shaft diameter |
| Answer» E. | |
| 29. |
Lubricant used for ball bearing is usually___________? |
| A. | graphite |
| B. | grease |
| C. | mineral oil |
| D. | molasses |
| Answer» C. mineral oil | |
| 30. |
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 5% |
| B. | The rotor will not run |
| C. | The rotor will run at very high speed |
| D. | The torque produced will be very large |
| Answer» C. The rotor will run at very high speed | |
| 31. |
In the squirrel-cage induction motor the rotor slots are usually given slight skew__________? |
| A. | to reduce the magnetic hum and locking tendency of the rotor |
| B. | to increase the tensile strength of the rotor bars |
| C. | to ensure easy fabrication |
| D. | none of the above |
| Answer» B. to increase the tensile strength of the rotor bars | |
| 32. |
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 |
| Answer» C. external capacitance to the rotor | |
| 33. |
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. | |
| 34. |
The power scale of circle diagram of an induction motor can be found from__________? |
| A. | stator resistance test |
| B. | no-load test only |
| C. | short-circuit test only |
| D. | none of the above |
| Answer» D. none of the above | |
| 35. |
The low power factor of induction motor is due to___________? |
| A. | rotor leakage reactance |
| B. | stator reactance |
| C. | the reactive lagging magnetizing current necessary to generate the magnetic flux |
| D. | all of the above |
| Answer» E. | |
| 36. |
An induction motor can run at synchronous speed when____________? |
| A. | it is run on load |
| B. | it is run in reverse direction |
| C. | it is run on voltage higher than the rated voltage |
| D. | e.m.f. is injected in the rotor circuit |
| Answer» E. | |
| 37. |
The shape of the torque/slip curve of induction motor is__________? |
| A. | parabola |
| B. | hyperbola |
| C. | rectangular parabola |
| D. | straigth line |
| Answer» D. straigth line | |
| 38. |
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. | |
| 39. |
Insertion of resistance in the rotor of an induction motor to develop a given torque? |
| A. | decreases the rotor current |
| B. | increases the rotor current |
| C. | rotor current becomes zero |
| D. | rotor current rernains same |
| Answer» E. | |
| 40. |
The vafcie of transformation ratio of an induction motor can be found by__________? |
| A. | open-circuit test only |
| B. | short-circuit test only |
| C. | stator resistance test |
| D. | none of the above |
| Answer» C. stator resistance test | |
| 41. |
Which is of the following data is required to draw the circle diagram for an induction motor ? |
| A. | Block rotor test only |
| B. | No load test only |
| C. | Block rotor test and no-load test |
| D. | Block rotor test, no-load test and stator resistance test |
| Answer» E. | |
| 42. |
In a three-phase induction motor__________? |
| A. | power factor at starting is high as compared to that while running |
| B. | power factor at starting is low as compared to that while running |
| C. | power factor at starting in the same as that while running |
| Answer» C. power factor at starting in the same as that while running | |
| 43. |
In case of 3-phase induction motors, plugging means__________? |
| A. | pulling the motor directly on line without a starter |
| B. | locking of rotor due to harmonics |
| C. | starting the motor on load which is more than the rated load |
| D. | interchanging two supply phases for quick stopping |
| Answer» E. | |
| 44. |
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 |
| Answer» B. reduce copper losses | |
| 45. |
Temperature of the stator winding of a three phase induction motor is obtained by___________? |
| A. | resistance rise method |
| B. | thermometer method |
| C. | embedded temperature method |
| D. | all above methods |
| Answer» E. | |
| 46. |
If a 3-phase supply is given to the stator and rotor is short circuited rotor will move___________? |
| A. | in the opposite direction as the direction of the rotating field |
| B. | in the same direction as the direction of the field |
| C. | in any direction depending upon phase squence of supply |
| Answer» C. in any direction depending upon phase squence of supply | |
| 47. |
In induction motor, percentage slip depends on__________? |
| A. | supply frequency |
| B. | supply voltage |
| C. | copper losses in motor |
| D. | none of the above |
| Answer» D. none of the above | |
| 48. |
When /?2 is the rotor resistance, .X2 the rotor reactance at supply frequency and s the slip, then the condition for maximum torque under running conditions will be_____________? |
| A. | sR2X2 = 1 |
| B. | sR2 = X2 |
| C. | R2 = sX2 |
| D. | R2 = s2X2 |
| Answer» D. R2 = s2X2 | |
| 49. |
It is advisable to avoid line starting of induction motor and use starter because____________? |
| A. | it will run in reverse direction |
| B. | it will pick up very high speed and may go out of step |
| C. | motor takes five to seven times its full load current |
| D. | starting torque is very high |
| Answer» D. starting torque is very high | |
| 50. |
The efficiency of an induction motor can be expected to be nearly____________? |
| A. | 60 to 90% |
| B. | 80 to 90% |
| C. | 95 to 98% |
| D. | 99% |
| Answer» C. 95 to 98% | |