MCQOPTIONS
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MCQOPTIONS
This section includes 22 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. |
In a capacitor start and run motors the function of the running capacitor in series with the auxiliary winding is to |
| A. | improve power factor |
| B. | increase overload capacity |
| C. | reduce fluctuations in torque |
| D. | to improve torque |
| Answer» B. increase overload capacity | |
| 2. |
In a capacitor start motor, the phase displacement between starting and running winding can be nearly |
| A. | 10 |
| B. | 30 |
| C. | 60 |
| D. | 90 |
| Answer» E. | |
| 3. |
Starting winding of a single phase motor of a refrigerator is disconnected from the circuit by means of a |
| A. | magnetic relay |
| B. | thermal relay |
| C. | centrifugal switch |
| D. | none of the above |
| Answer» B. thermal relay | |
| 4. |
Centrifugal switch disconnects the auxiliary winding of the motor at about ____ percent of synchronous speed |
| A. | 30 to 40 |
| B. | 70 to 80 |
| C. | 80 to 90 |
| D. | 100 |
| Answer» C. 80 to 90 | |
| 5. |
Two-value capacitor motor finds increased application as compressor motor in small home air-conditioners because |
| A. | it is comparatively cheaper |
| B. | it has almost non-destructible capacitor |
| C. | it has low starting as well as running currents at relatively high power factor |
| D. | it is quiet in operation |
| Answer» D. it is quiet in operation | |
| 6. |
If the centrifugal switch of a two-value capacitor motor using two capacitors fails to open then |
| A. | motor will not come upto speed |
| B. | motor will not carry the load |
| C. | current drawn by the motor will be excessively high |
| D. | electrolytic capacitor will, in all probability, suffer break down |
| Answer» E. | |
| 7. |
To reverse the direction of rotation of acapacitor start motor while it is running we should |
| A. | disconnect motor from the supply till it stops then reconnect it to supply with reversed connection of main or auxiliary winding |
| B. | disconnect motor from supply and immediately reconnect it to supply with reversed connections of the main winding |
| C. | reverse the direction of connection of the auxiliary winding and after motor comes to rest then connect auxiliary winding to the supply |
| D. | reverse the direction of connections of the auxiliary winding and im-mediately connect it to supply |
| Answer» B. disconnect motor from supply and immediately reconnect it to supply with reversed connections of the main winding | |
| 8. |
In case of a reluctance motor, when the load is increased so that it cannot maintain synchronous speed the motor will |
| A. | become unstable |
| B. | draw excessive armature current and may burn out |
| C. | fall out of synchronism and come to stand still |
| D. | run as induction motor |
| Answer» E. | |
| 9. |
Which of the following statements regarding repulsion-start induction motor is incorrect ? |
| A. | It requires more maintenance of commutator and other mechanical devices |
| B. | It makes quite a bit of noise on starting |
| C. | In fractional horse power motors, it has replaced the capacitor motors |
| D. | It is not easily reversed |
| Answer» D. It is not easily reversed | |
| 10. |
After the starting winding of a single phase induction motor is disconnected from supply, it continues to run only on |
| A. | running winding |
| B. | rotor winding |
| C. | field winding |
| D. | compensating winding |
| Answer» B. rotor winding | |
| 11. |
Which of the following statements regarding single-phase induction motoris correct ? |
| A. | It requires only one winding |
| B. | It can rotate in one direction only |
| C. | It is self-starting |
| D. | It is not self-starting |
| Answer» E. | |
| 12. |
When a D.C. series motor is connected to A.C. supply, the power factor will be low because of |
| A. | high inductance of field and armature circuits |
| B. | induced current in rotor due to variations of flux |
| C. | fine copper wire winding |
| D. | none of the above |
| Answer» B. induced current in rotor due to variations of flux | |
| 13. |
The direction of rotation of universal motor can be reversed the by reversing the flow of current through |
| A. | armature winding |
| B. | field winding |
| C. | either armature winding or field winding |
| D. | none of the above |
| Answer» D. none of the above | |
| 14. |
As hysteresis motors are free from mechanical and magnetic vibrations therefore these are considered as suitable for |
| A. | fans |
| B. | blowers |
| C. | sound equipment |
| D. | mixer grinders |
| Answer» D. mixer grinders | |
| 15. |
If the centrifugal switch does not open at 70 to 80 percent of synchronous speed of motor, it would result in |
| A. | damage to the starting winding |
| B. | damage to the centrifugal switch |
| C. | overloading of running winding |
| D. | none of the above |
| Answer» B. damage to the centrifugal switch | |
| 16. |
The rotor slots, in an induction motor, are usually not quite parallel to the shaft because it |
| A. | improves the efficiency |
| B. | helps the rotor teeth to remain under the stator teeth |
| C. | helps in reducing the tendency of the rotor teeth to remain under the stator teeth |
| D. | improves the power factor |
| Answer» D. improves the power factor | |
| 17. |
Which of the following single-phase motors is suitable for timing and control purposes ? |
| A. | Reluctance motor |
| B. | Series motor |
| C. | Repulsion motor |
| D. | Universal motor |
| Answer» B. Series motor | |
| 18. |
Which of the following single-phase induction motors is generally used in time phonographs ? |
| A. | Resistance start |
| B. | Capacitor start capacitor run |
| C. | Shaded pole |
| D. | Universal |
| Answer» D. Universal | |
| 19. |
If a particular application needs high speed and high starting torque, then which of the following motor will be preferred ? |
| A. | Universal motor |
| B. | Shaded pole type motor |
| C. | Capacitor start motor |
| D. | Capacitor start and run motor |
| Answer» B. Shaded pole type motor | |
| 20. |
The running winding of a single phase motor on testing with meggar is found to be ground. Most probable location of the ground will be |
| A. | at the end connections |
| B. | at the end terminals |
| C. | anywhere on the winding inside a slot |
| D. | at the slot edge where coil enters or comes out of the slot |
| Answer» E. | |
| 21. |
A capacitor-start single phase induction motor is switched on to supply with its capacitor replaced by an inductor of equivalent reactance value. It will |
| A. | start and then stop |
| B. | start and run slowly |
| C. | start and run at rated speed |
| D. | not start at all |
| Answer» E. | |
| 22. |
Direction of rotation of a split phase motor can be reversed by reversing the connection of |
| A. | running winding only |
| B. | starting winding only |
| C. | either (a) or (b) |
| D. | both (a) and (b) |
| Answer» D. both (a) and (b) | |