MCQOPTIONS
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MCQOPTIONS
This section includes 244 Mcqs, each offering curated multiple-choice questions to sharpen your Power Electronics knowledge and support exam preparation. Choose a topic below to get started.
| 1. |
Which of the following motors is preferred for boom hoist of a travelling crane? |
| A. | Single phase motor |
| B. | Synchronous motor |
| C. | A.C. slip ring motor |
| D. | Ward-Leonard controlled D.C. shunt motor |
| Answer» D. Ward-Leonard controlled D.C. shunt motor | |
| 2. |
Which of the following is the voltage for single phase A.C. system ? |
| A. | 22 V |
| B. | 440 V |
| C. | 5 kV |
| D. | 15 kV |
| Answer» B. 440 V | |
| 3. |
A pole changing type squirrel cage motor used in derricks has four, eight and twenty four poles. In this the medium speed is used for |
| A. | lifting |
| B. | hoisting |
| C. | lowering |
| D. | landing the load. |
| Answer» B. hoisting | |
| 4. |
A reluctance motor on over-load runs as |
| A. | synchronous motor |
| B. | induction motor |
| C. | either of the two. |
| D. | all |
| Answer» C. either of the two. | |
| 5. |
Which of the following happens when star-delta starter is used ? |
| A. | Starting voltage is reduced |
| B. | Starting current is reduced |
| C. | Both (A) and (B) |
| D. | None of the above |
| Answer» D. None of the above | |
| 6. |
By the use of which of the following DC can be obtained from AC? |
| A. | Silicon diodes |
| B. | Mercury arc rectifier |
| C. | Motor generator set |
| D. | Any of the above |
| Answer» E. | |
| 7. |
The travelling speed of cranes varies from |
| A. | 20 to 30 m/s |
| B. | 10 to 15 m/s |
| C. | 5 to 10 m/s |
| D. | 1 to 2.5 m/s |
| Answer» E. | |
| 8. |
The specific energy consumption of a train depends on which of the following ? |
| A. | Acceleration and retardation |
| B. | Gradient |
| C. | Distance covered |
| D. | All of the above |
| Answer» D. All of the above | |
| 9. |
Power for lighting in passanger coach, in a long distance electric train, is provided |
| A. | directly through overhead electric line |
| B. | through individual generator of bogie and batteries |
| C. | through rails |
| D. | through locomotive |
| Answer» C. through rails | |
| 10. |
...........is preferred for synthetic fibre mails |
| A. | Synchronous motor |
| B. | Reluctance motor |
| C. | Series motor |
| D. | Shunt motor |
| Answer» C. Series motor | |
| 11. |
When quick speed reversal is a consideration, the motor preferred is |
| A. | synchronous motor |
| B. | squirrel cage induction motor |
| C. | wound rotor induction motor |
| D. | dc motor. |
| Answer» E. | |
| 12. |
Which of the following motors is used for elevators ? |
| A. | Induction motor |
| B. | Synchronous motor |
| C. | Capacitor start single phase motor |
| D. | Any of the above |
| Answer» B. Synchronous motor | |
| 13. |
The least expensive drive is |
| A. | Belt drive |
| B. | Rope drive |
| C. | Chain drive |
| D. | Any of the above |
| Answer» B. Rope drive | |
| 14. |
Series motor is not suited for traction duty due to which of the following account ? |
| A. | Less current drain on the heavy load torque |
| B. | Current surges after temporary switching off supply |
| C. | Self relieving property |
| D. | Commutating property at heavy load |
| Answer» C. Self relieving property | |
| 15. |
The size of a excavator is usually expressed in terms of |
| A. | cubic meters |
| B. | travel in meters |
| C. | angle of swing |
| D. | 'crowd' motion |
| Answer» B. travel in meters | |
| 16. |
For a motor-generator set which of the following motors will be preferred ? |
| A. | Synchronous motor |
| B. | Slip ring induction motor |
| C. | Pole changing induction motor |
| D. | Squirrel cage induction motor |
| Answer» B. Slip ring induction motor | |
| 17. |
Rotor of the motor is usually supported on........... bearings |
| A. | Ball or roller |
| B. | Needle |
| C. | Thrust |
| D. | Bush |
| Answer» B. Needle | |
| 18. |
The slip power recovery scheme is used in induction motor for speed control in the range |
| A. | Above synchronous speed |
| B. | Below synchronous speed |
| C. | Both above and below synchronous speed |
| D. | None of the above |
| Answer» D. None of the above | |
| 19. |
Load torques can be classified into how many types? |
| A. | Three |
| B. | Two |
| C. | Four |
| D. | Five |
| Answer» C. Four | |
| 20. |
Who made the first solar cell? |
| A. | Gerald Pearson |
| B. | Tim Bell |
| C. | Tim Cook |
| D. | Nicola Tesla |
| Answer» B. Tim Bell | |
| 21. |
Which of the following is the advantage of electric braking ? |
| A. | It avoids wear of track |
| B. | Motor continues to remain loaded during braking |
| C. | It is instantaneous |
| D. | More heat is generated during braking |
| Answer» B. Motor continues to remain loaded during braking | |
| 22. |
Long distance railways use which of the following ? |
| A. | 200 V D.C. |
| B. | 25 kV single phase A.C. |
| C. | 25 kV two phase A.C. |
| D. | 25 kV three phase A.C. |
| Answer» C. 25 kV two phase A.C. | |
| 23. |
Which ofthefollowing motors is preferred when smooth and precise speed control over a wide range is desired ? |
| A. | D.C. motor |
| B. | Squirrel cage induction motor |
| C. | Wound rotor induction motor |
| D. | Synchronous motor |
| Answer» B. Squirrel cage induction motor | |
| 24. |
For a D.C. shunt motor which of the following is incorrect 7 |
| A. | Unsuitable for heavy duty starting |
| B. | Torque varies as armature current |
| C. | Torque-armature current is a straight line |
| D. | Torque is zero for zero armature current |
| Answer» B. Torque varies as armature current | |
| 25. |
In ........the speed can be varied by changing the position of brushes |
| A. | Slip ring motor |
| B. | Schrage motor |
| C. | Induction motor |
| D. | Repulsion motor |
| Answer» C. Induction motor | |
| 26. |
The characteristics of drive for. crane hoisting and lowering is |
| A. | smooth movement |
| B. | precise control |
| C. | fast speed control |
| D. | all of the above. |
| Answer» E. | |
| 27. |
Which of the following types of motor and enclosure is safest |
| A. | Totally enclosed |
| B. | Totally enclosed fan cooled |
| C. | Open time |
| D. | Semi closed |
| Answer» C. Open time | |
| 28. |
In DC chopper, the waveform for input and output voltages is respectively __________ |
| A. | Discontinuous and Continuous |
| B. | Continuous and Discontinuous |
| C. | Both continuous |
| D. | Both discontinuous |
| Answer» C. Both continuous | |
| 29. |
Speed-time curve of main line service differs from those of urban and suburbanservices on following account |
| A. | it has longer free running period |
| B. | it has longer coasting period |
| C. | accelerating and braking periods are comparatively smaller |
| D. | all of the above |
| Answer» E. | |
| 30. |
Electric drive is becoming more and more popular because |
| A. | It is simple, cleaned, compact and reliable |
| B. | It provides easy and smooth control, flexibility in layout, easy starting and facility for remote control |
| C. | It is cheaper in initial as well as in maintenance cost |
| D. | All of the above |
| Answer» E. | |
| 31. |
For very high speed ratio the indispensable drive is |
| A. | Direct drive |
| B. | Rope Drive |
| C. | Chain drive |
| D. | Any of the above |
| Answer» C. Chain drive | |
| 32. |
has least range of speed control. |
| A. | Slip ring induction motor |
| B. | Synchronous motor |
| C. | C. shunt motor |
| Answer» C. C. shunt motor | |
| 33. |
Which of the following is preferred for automatic drives ? |
| A. | Synchronous motors |
| B. | Squirrel cage induction motor |
| C. | Ward Leonard controlled dc motors |
| D. | Any of the above. |
| Answer» D. Any of the above. | |
| 34. |
What is the condition for the steady-state operation of the motor? |
| A. | Load torque > Motor torque |
| B. | Load torque <<<< Motor torque |
| C. | Load torque = Motor torque |
| D. | Load torque < Motor torque |
| Answer» D. Load torque < Motor torque | |
| 35. |
A chopper behaves as a __________ |
| A. | DC equivalent of AC switching device |
| B. | DC equivalent of AC transformer |
| C. | DC equivalent of AC relay |
| D. | AC equivalent of circuit breaker |
| Answer» C. DC equivalent of AC relay | |
| 36. |
Which type of drive can be used for hoisting machinery |
| A. | AC slip ring motor |
| B. | Ward Leonard controlled DC shunt motor |
| C. | DC compound motor |
| D. | Any of the above. |
| Answer» E. | |
| 37. |
Most commonly used ac motor is |
| A. | Synchronous motor |
| B. | Slip ring induction motor |
| C. | Squirrel cage induction motor |
| D. | ac commutator induction motor. |
| Answer» D. ac commutator induction motor. | |
| 38. |
A wound rotor induction motor is preferred over squirrel cage induction motor when the major consideration involved is |
| A. | high starting torque |
| B. | low starting current |
| C. | speed control over limited range |
| D. | all of the above. |
| Answer» E. | |
| 39. |
For crane travel which of the following motors is normally used ? |
| A. | Synchronous motor |
| B. | D.C. differentially compound motor |
| C. | Ward-Leonard controlled |
| D. | C. shunt motor |
| Answer» E. | |
| 40. |
For which off the following applications DC motors are still preferred? |
| A. | High operation |
| B. | Variable speed drive |
| C. | High starting torque |
| D. | Reversibility |
| Answer» C. High starting torque | |
| 41. |
Which of the following motor is preferred for synthetic fibre mills ? |
| A. | series motor |
| B. | reluctance motor |
| C. | shunt motor |
| D. | synchronous motor. |
| Answer» C. shunt motor | |
| 42. |
In synthetic fibre mills motor with |
| A. | constant speeds are preferred |
| B. | high starting torque are preferred |
| C. | variable speed are preferred |
| D. | low starting torque are preferred. |
| Answer» B. high starting torque are preferred | |
| 43. |
In jaw crushers, a motor has to often start against |
| A. | low load |
| B. | medium load |
| C. | normal load |
| D. | heavy load. |
| Answer» E. | |
| 44. |
Wound rotor and squirrel-cage motors with high slip which develop maximumtorque at stand still are used for |
| A. | machine tools |
| B. | presses and punches |
| C. | elevators |
| D. | all of the above. |
| Answer» C. elevators | |
| 45. |
While selecting a motor for air-conditioner the feature of utmost importance is |
| A. | Type of enclosure |
| B. | Type of bearing |
| C. | Noise |
| D. | Power transmission arrangement |
| Answer» D. Power transmission arrangement | |
| 46. |
To save the energy during braking |
| A. | dynamic braking is used |
| B. | plugging is used |
| C. | regenerative braking is used |
| D. | mechanical braking is used. |
| Answer» D. mechanical braking is used. | |
| 47. |
When smooth and precise speed control over a wide range is desired, the motorpreferred is |
| A. | synchronous motor |
| B. | squirrel cage induction motor |
| C. | wound rotor induction motor |
| D. | dc motor. |
| Answer» E. | |
| 48. |
The motor commonly used in computers and digital systems is |
| A. | dc shunt motor |
| B. | Induction motor |
| C. | Stepper motor |
| D. | Synchronous motor. |
| Answer» C. Stepper motor | |
| 49. |
Which of the following motors is preferred for boom host of a travelling crane? |
| A. | Single phase motor |
| B. | Synchronous motor |
| C. | AC slip ring motor |
| D. | Ward Leonard controlled DC shunt motor |
| Answer» D. Ward Leonard controlled DC shunt motor | |
| 50. |
The characteristics of drive for crane hoisting and lowering are which off thefollowing? |
| A. | Precise control |
| B. | Smooth movement |
| C. | Fast speed control |
| D. | All of the above |
| Answer» E. | |