MCQOPTIONS
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MCQOPTIONS
This section includes 61 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. |
Which of the following motors one will choose to drive the rotary compressor ? |
| A. | D.C. shunt motor |
| B. | D.C. series motor |
| C. | Universal motor |
| D. | Synchronous motor |
| Answer» E. | |
| 2. |
To get the speed of D.C, motor below the normal without wastage of electrical energyis used. |
| A. | Ward Leonard control |
| B. | rheostatic control |
| C. | any of the above method |
| D. | none of the above method |
| Answer» B. rheostatic control | |
| 3. |
Which D.C. motor is generally preferred for cranes and hoists ? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Cumulatively compounded motor |
| D. | Differentially compounded motor |
| Answer» B. Shunt motor | |
| 4. |
For which of the following applications a D.C. motor is preferred over an A.C. motor ? |
| A. | Low speed operation |
| B. | High speed operation |
| C. | Variable speed operation |
| D. | Fixed speed operation |
| Answer» D. Fixed speed operation | |
| 5. |
In case the back e.m.f. and the speed of a D.C. motor are doubled, the torque developedby the motor will |
| A. | remain unchanged |
| B. | reduce to one-fourth value |
| C. | increase four folds |
| D. | be doubled |
| Answer» B. reduce to one-fourth value | |
| 6. |
Which D.C. motor is preferred for elevators ? |
| A. | Shunt motor |
| B. | Series motor |
| C. | Differential compound motor |
| D. | Cumulative compound motor |
| Answer» E. | |
| 7. |
Which of the following motors is most suitable for signalling devices and many kindsof timers ? |
| A. | D.C. shunt motor |
| B. | D.C. series motor |
| C. | Induction motor |
| D. | Reluctance motor |
| Answer» E. | |
| 8. |
According to Fleming's left-hand rule, when the forefinger points in the direction of the field or flux, the middle finger will point in the direction of |
| A. | current in the conductor aovtaat of conductor |
| B. | resultant force on conductor |
| C. | none of the above |
| Answer» B. resultant force on conductor | |
| 9. |
One D.C. motor drives another D.C. motor. The second D.C. motor when excited anddriven |
| A. | runs as a generator |
| B. | does not run as a generator |
| C. | also runs as a motor comes to stop after sometime |
| D. | none |
| Answer» B. does not run as a generator | |
| 10. |
The mechanical power developed by a shunt motor will be maximum when the ratioof back e.m.f. to applied voltage is |
| A. | 4.0 |
| B. | 2.0 |
| C. | 1.0 |
| D. | 0.5 |
| Answer» E. | |
| 11. |
D.C. generators are installed near the load centres to reduce |
| A. | iron losses |
| B. | line losses |
| C. | sparking |
| D. | corona losses |
| Answer» C. sparking | |
| 12. |
D.C. motor is to a drive a load which is almost nil for certain part of the load cycleand peak value for short duration. We will select this |
| A. | series motor |
| B. | shunt motor |
| C. | compound motor |
| D. | any of the above |
| Answer» D. any of the above | |
| 13. |
The speed of a motor falls from 1100 r.p.m. at no-load to 1050 r.p.m. at rated load. Thespeed regulation of the motor is |
| A. | 2.36% |
| B. | 4.76% |
| C. | 6.77% |
| D. | 8.84% |
| Answer» C. 6.77% | |
| 14. |
Which of the following law/rule can he used to determine the direction of rotation ofD.C. motor ? |
| A. | Lenz's law |
| B. | Faraday's law |
| C. | Coloumb's law |
| D. | Fleming's left-hand rule |
| Answer» E. | |
| 15. |
Why are the D.C. motors preferred for traction applications ? |
| A. | Torque and speed are inversely proportional to armature current |
| B. | Torque is proportional to armature current |
| C. | Torque is proportional to square root of armature current |
| D. | The speed is inversely proportional to the torque and the torque is proportional to square of armature current |
| Answer» E. | |
| 16. |
Which of the following motor is preferred for operation in highly explosiveatmosphere ? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Air motor |
| D. | Battery operated motor |
| Answer» D. Battery operated motor | |
| 17. |
The speed of a D.C. shunt motor is required to be more than full load speed. This ispossible by |
| A. | reducing the field current |
| B. | decreasing the armature current |
| C. | increasing the armature current |
| D. | increasing the excitation current |
| Answer» B. decreasing the armature current | |
| 18. |
As -the load is increased the speed of D.C. shunt motor will |
| A. | reduce slightly |
| B. | increase slightly |
| C. | increase proportionately |
| D. | remains unchanged |
| Answer» B. increase slightly | |
| 19. |
Which of the following steps is likely to result in reduction of hysteresis loss in a D.C.generator ? |
| A. | Providing laminations in armature core |
| B. | Providing laminations in stator |
| C. | Using non-magnetic material for frame |
| D. | Using material of low hysteresis co-efficient for armature core material |
| Answer» E. | |
| 20. |
B. DC MOTOR1. No-load speed of which of the following motor will be highest ? |
| A. | Shunt motor |
| B. | Series motor |
| C. | Cumulative compound motor |
| D. | Differentiate compound motor |
| Answer» C. Cumulative compound motor | |
| 21. |
Which of the following loss in a D.C. generator varies significantly with the loadcurrent ? |
| A. | Field copper loss |
| B. | Windage loss |
| C. | Armature copper loss |
| D. | None of the above |
| Answer» D. None of the above | |
| 22. |
Which of the following method of speed control of D.C. machine will offer minimum efficiency ? |
| A. | Voltage control method |
| B. | Field control method |
| C. | Armature control method |
| D. | All above methods |
| Answer» D. All above methods | |
| 23. |
Which of the following losses are significantly reduced by laminating the core of aD.C. generator ? |
| A. | Hysteresis losses |
| B. | Eddy current losses |
| C. | Copper losses |
| D. | Windage losses |
| Answer» C. Copper losses | |
| 24. |
Which method of braking is generally used in elevators ? |
| A. | Plugging |
| B. | Regenerative braking |
| C. | Rheostatic braking |
| D. | None of the above |
| Answer» B. Regenerative braking | |
| 25. |
In a D.C. shunt motor, under the conditions of maximum power, the current in thearmature will be |
| A. | almost negligible |
| B. | rated full-load current |
| C. | less than full-load current |
| D. | more than full-load current |
| Answer» E. | |
| 26. |
Which D.C. motor has got maximum self relieving property ? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Cumulatively compounded motor |
| D. | Differentially compounded motor |
| Answer» B. Shunt motor | |
| 27. |
Buses, trains, trolleys, hoists, cranes require high starting torque and therefore makeuse of |
| A. | D.C. series motor |
| B. | D.C. shunt motor |
| C. | induction motor |
| D. | all of above motors |
| Answer» B. D.C. shunt motor | |
| 28. |
Which one of the following is not the function of pole shoes in a D.C. machine ? |
| A. | To reduce eddy current loss |
| B. | To support the field coils |
| C. | To spread out flux for better unifor-mity |
| D. | To reduce the reluctance of the mag-netic path |
| Answer» B. To support the field coils | |
| 29. |
Which of the following tests will be suitable for testing two similar D.C. series motorsof large capacity ? |
| A. | Swinburne's test |
| B. | Hopkinson's test |
| C. | Field test |
| D. | Brake test |
| Answer» D. Brake test | |
| 30. |
For which types of D.C. motor, dynamic braking is generally used ? |
| A. | Shunt motors |
| B. | Series motors |
| C. | Compound motors |
| D. | All of the above |
| Answer» E. | |
| 31. |
Which of the following motor has the poorest speed regulation ? |
| A. | Shunt motor |
| B. | Series motor |
| C. | Differential compound motor |
| D. | Cumulative compound motor |
| Answer» C. Differential compound motor | |
| 32. |
During rheostat braking of D.C. series motors |
| A. | motor is run as a generator |
| B. | motor is reversed in direction |
| C. | motor is run at reduced speed |
| D. | none |
| Answer» B. motor is reversed in direction | |
| 33. |
If a D.C. motor is to be selected for conveyors, which rriotor would be preferred ? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Differentially compound motor |
| D. | Cumulative compound motor |
| Answer» B. Shunt motor | |
| 34. |
Which of the following load normally needs starting torque more than the ratedtorque? |
| A. | Blowers |
| B. | Conveyors |
| C. | Air compressors |
| D. | Centrifugal pumps |
| Answer» C. Air compressors | |
| 35. |
If the terminals of armature of D.C. motor are interchanged, this action will offerfollowing kind of braking |
| A. | regenerative |
| B. | plugging |
| C. | dynamic braking |
| D. | none of the above |
| Answer» C. dynamic braking | |
| 36. |
For constant torque drive which speed control method is preferred ? |
| A. | Field control |
| B. | Armature voltage control |
| C. | Shunt armature control |
| D. | Mechanical loading system |
| Answer» C. Shunt armature control | |
| 37. |
In case-the conditions for maximum power for a D.C. motor are established, theefficiency of the motor will be |
| A. | 100% |
| B. | around 90% |
| C. | anywhere between 75% and 90% |
| D. | less than 50% |
| Answer» E. | |
| 38. |
Which D.C. motor will be suitable alongwith flywheel for intermittent light and heavyloads? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Cumulatively compounded motor |
| D. | Differentially compounded motor |
| Answer» D. Differentially compounded motor | |
| 39. |
Which one of the following is not necessarily the advantage of D.C. motors over A.C.motors ? |
| A. | Low cost |
| B. | Wide speed range |
| C. | Stability |
| D. | High starting torque. |
| Answer» B. Wide speed range | |
| 40. |
Following motor is used where high starting torque and wide speed range control isrequired. |
| A. | Single phase capacitor start |
| B. | Induction motor |
| C. | Synchronous motor |
| D. | D.C. motor |
| Answer» E. | |
| 41. |
By looking at which part of the motor, it can be easily confirmed that a particularmotor is D.C. motor? |
| A. | Frame |
| B. | Shaft |
| C. | Commutator |
| D. | Stator |
| Answer» D. Stator | |
| 42. |
Flywheel is used with D.C. compound motor to reduce the peak demand by the motor,compound motor will have to be |
| A. | level compounded |
| B. | under compounded |
| C. | cumulatively compounded |
| D. | differentially compounded |
| Answer» D. differentially compounded | |
| 43. |
Which D.C. motor will be preferred for machine tools ? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Cumulative compound motor |
| D. | Differential compound motor |
| Answer» C. Cumulative compound motor | |
| 44. |
The losses occurring in a D.C. generator are given below. Which loss is likely to havehighest proportion at rated load of the generator ? |
| A. | hysteresis loss |
| B. | field copper loss |
| C. | armature copper loss |
| D. | eddy current loss |
| Answer» D. eddy current loss | |
| 45. |
In case of conductively compensated D.C. series motors, the compensating winding isprovided |
| A. | as separately wound unit |
| B. | in parallel with armature winding |
| C. | in series with armature winding |
| D. | in parallel with field winding |
| Answer» D. in parallel with field winding | |
| 46. |
Which of the following motors is usually used in house-hold refrigerators ? |
| A. | D.C. shunt motor |
| B. | D.C. series motor |
| C. | Single phase induction motor (split phase start or induction run motor) |
| D. | Reluctance motor |
| Answer» D. Reluctance motor | |
| 47. |
Which motor should not be started on no-load ? |
| A. | Series motor |
| B. | Shunt motor |
| C. | Cumulatively compounded motor |
| D. | Differentially compounded motor. |
| Answer» B. Shunt motor | |
| 48. |
Which of the following application requires high starting torque ? |
| A. | Lathe machine |
| B. | Centrifugal pump |
| C. | Locomotive |
| D. | Air blower |
| Answer» D. Air blower | |
| 49. |
PMMDC can only be armature controlled. |
| A. | True |
| B. | False |
| Answer» B. False | |
| 50. |
A PMMDC motor has an armature resistance of 4.2 ohms. When 6 V supply is applied to motor it runs at 1215 rpm drawing 14.5 mA on no-load. The rotational losses is? |
| A. | 86.1 mW |
| B. | 86.1 W |
| C. | 8.6 W |
| D. | 8.6 mW |
| Answer» B. 86.1 W | |