MCQOPTIONS
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MCQOPTIONS
This section includes 100 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. |
Insertion of resistance in the rotcir 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 rernains same |
| Answer» E. | |
| 2. |
Which of the following protection is normally not provided on small distribution transformers? |
| A. | verfluxing protection |
| B. | uchholz relay |
| C. | vercurrent protection |
| D. | ll of the above |
| Answer» C. vercurrent protection | |
| 3. |
The maximum efficiency of a distribution transformer is |
| A. | t no load |
| B. | t 50% full load |
| C. | t 80% full load |
| D. | t full load |
| Answer» C. t 80% full load | |
| 4. |
Natural air cooling is generally restricted for transformers up to |
| A. | .5 MVA |
| B. | MVA |
| C. | 5 MVA |
| D. | 0 MVA |
| Answer» B. MVA | |
| 5. |
Which of the following properties is not necessarily desirable for the material for transformer core? |
| A. | ow hysteresis loss |
| B. | igh permeability |
| C. | igh thermal conductivity |
| D. | dequate mechanical strength |
| Answer» D. dequate mechanical strength | |
| 6. |
Which of the following property is not necessarily desirable in the material for transformer core? |
| A. | echanical strength |
| B. | ow hysteresis loss |
| C. | igh thermal conductivity |
| D. | igh permeability |
| Answer» D. igh permeability | |
| 7. |
Efficiency of a power transformer is of the order of |
| A. | 00 per cent |
| B. | 8 per cent |
| C. | 0 per cent |
| D. | 5 per cent |
| Answer» C. 0 per cent | |
| 8. |
Which of the following is not a part of transformer installation? |
| A. | onservator |
| B. | reather |
| C. | uchholz relay |
| D. | xciter |
| Answer» E. | |
| 9. |
The 'cogging' of an induction motor can be avoided by |
| A. | roper ventilation |
| B. | sing DOL starter |
| C. | uto-transformer starter |
| D. | aving number of rotor slots more or less than the number of stator slots (not equal) |
| Answer» E. | |
| 10. |
The secondary of a current transformer is always short-circuited under operating conditions because it |
| A. | voids core saturation and high voltage induction |
| B. | s safe to human beings |
| C. | rotects the primary circuit |
| D. | one of the above |
| Answer» B. s safe to human beings | |
| 11. |
The power factor of an induction motor under no-load conditions will be closer to |
| A. | .2 lagging |
| B. | .2 leading |
| C. | .5 leading |
| D. | nity |
| Answer» B. .2 leading | |
| 12. |
The voltage transformation ratio of a transformer is equal to the ratio of |
| A. | rimary turns to secondary turns |
| B. | econdary current to primary current |
| C. | econdary induced e.m.f. to primary induced e.m.f. |
| D. | econdary terminal voltage to primary applied voltage |
| Answer» D. econdary terminal voltage to primary applied voltage | |
| 13. |
In a transformer the energy is conveyed from primary to secondary |
| A. | hrough cooling coil |
| B. | hrough air |
| C. | y the flux |
| D. | one of the above |
| Answer» D. one of the above | |
| 14. |
An open-circuit test on a transformer is conducted primarily to measure |
| A. | nsulation resistance |
| B. | opper loss |
| C. | ore loss |
| D. | otal loss |
| Answer» D. otal loss | |
| 15. |
A common method of cooling a power transformer is |
| A. | atural air cooling |
| B. | ir blast cooling |
| C. | il cooling |
| D. | ny of the above |
| Answer» D. ny of the above | |
| 16. |
In a step-down transformer, there is a change of 15 A in the load current. This results in change of supply current of |
| A. | ess than 15 A |
| B. | ore than 15 A |
| C. | 5 A |
| D. | one of the above |
| Answer» B. ore than 15 A | |
| 17. |
No-load current of a transformer has |
| A. | as high magnitude and low power factor |
| B. | as high magnitude and high power factor |
| C. | as small magnitude and high power factor |
| D. | as small magnitude and low power factor |
| Answer» E. | |
| 18. |
The permissible flux density in case of cold rolled grain oriented steel is around |
| A. | .7 Wb/m² |
| B. | .7 Wb/m² |
| C. | .7 Wb/m² |
| D. | .7 Wb/m² |
| Answer» B. .7 Wb/m² | |
| 19. |
The path of the magnetic flux in transformer should have |
| A. | igh reluctance |
| B. | ow reactance |
| C. | igh resistance |
| D. | ow resistance |
| Answer» C. igh resistance | |
| 20. |
Open circuit test on transformers is conducted to determine |
| A. | ysteresis losses |
| B. | opper losses |
| C. | ore losses |
| D. | ddy current losses |
| Answer» D. ddy current losses | |
| 21. |
Noise level test in a transformer is a |
| A. | pecial test |
| B. | outine test |
| C. | ype test |
| D. | one of the above |
| Answer» D. one of the above | |
| 22. |
An ideal transformer is one which has |
| A. | o losses and magnetic leakage |
| B. | nterleaved primary and secondary windings |
| C. | common core for its primary and secondary windings |
| D. | ore of stainless steel and winding of pure copper metal |
| Answer» B. nterleaved primary and secondary windings | |
| 23. |
Which type of winding is used in 3phase shell-type transformer? |
| A. | ircular type |
| B. | andwich type |
| C. | ylindrical type |
| D. | ectangular type |
| Answer» C. ylindrical type | |
| 24. |
Which motor is preferred for use in mines where explosive gases exist? |
| A. | ir motor |
| B. | nduction motor |
| C. | hunt motor |
| D. | ynchronous motor |
| Answer» B. nduction motor | |
| 25. |
Negative voltage regulation is indicative that the load is |
| A. | apacitive only |
| B. | nductive only |
| C. | nductive or resistive |
| D. | one of the above |
| Answer» B. nductive only | |
| 26. |
Primary winding of a transformer |
| A. | s always a low voltage winding |
| B. | s always a high voltage winding |
| C. | ould either be a low voltage or high voltage winding |
| D. | one of the above |
| Answer» D. one of the above | |
| 27. |
Losses which occur in rotating electric machines and do not occur in trans formers are |
| A. | riction and windage losses |
| B. | agnetic losses |
| C. | ysteresis and eddy current losses |
| D. | opper losses |
| Answer» B. agnetic losses | |
| 28. |
No-load on a transformer is carried out to determine |
| A. | opper loss |
| B. | agnetising current |
| C. | agnetising current and loss |
| D. | fficiency of the transformer |
| Answer» D. fficiency of the transformer | |
| 29. |
In Ns is the synchronous speed and s the slip, then actual running speed of an induction motor will be |
| A. | s |
| B. | .N. |
| C. | l-s)Ns |
| D. | Ns-l)s |
| Answer» D. Ns-l)s | |
| 30. |
When secondary of a current transformer is open-circuited its iron core will be |
| A. | ot because of heavy iron losses taking place in it due to high flux density |
| B. | ot because primary will carry heavy current |
| C. | ool as there is no secondary current |
| D. | one of above will happen |
| Answer» B. ot because primary will carry heavy current | |
| 31. |
In case of 3-phase induction motors, plugging means |
| A. | ulling the motor directly on line without a starter |
| B. | ocking of rotor due to harmonics |
| C. | tarting the motor on load which is more than the rated load |
| D. | nterchanging two supply phases for quick stopping |
| Answer» E. | |
| 32. |
The maximum load that a power transformer can carry is limited by its |
| A. | emperature rise |
| B. | ielectric strength of oil |
| C. | oltage ratio |
| D. | opper loss |
| Answer» D. opper loss | |
| 33. |
Natural oil cooling is used for transformers up to a rating of |
| A. | 000 kVA |
| B. | 000 kVA |
| C. | 00 kVA |
| D. | 50 kVA |
| Answer» B. 000 kVA | |
| 34. |
Which winding in a transformer has more number of turns? |
| A. | ow voltage winding |
| B. | igh voltage winding |
| C. | rimary winding |
| D. | econdary winding |
| Answer» C. rimary winding | |
| 35. |
In a power or distribution transformer about 10 per cent end turns are heavily insulated |
| A. | o withstand the high voltage drop due to line surge produced by the shunting capacitance of the end turns |
| B. | o absorb the line surge voltage and save the winding of transformer from damage |
| C. | o reflect the line surge and save the winding of a transformer from damage |
| D. | one of the above |
| Answer» B. o absorb the line surge voltage and save the winding of transformer from damage | |
| 36. |
The efficiency of a transformer, under heavy loads, is comparatively low because |
| A. | opper loss becomes high in proportion to the output |
| B. | ron loss is increased considerably |
| C. | oltage drop both in primary and secondary becomes large |
| D. | econdary output is much less as compared to primary input |
| Answer» B. ron loss is increased considerably | |
| 37. |
For the parallel operation of single phase transformers it is necessary that they should have |
| A. | ame efficiency |
| B. | ame polarity |
| C. | ame kVA rating |
| D. | ame number of turns on the secondary side. |
| Answer» C. ame kVA rating | |
| 38. |
Sumpner's test is conducted on transformers to determine |
| A. | emperature |
| B. | tray losses |
| C. | ll-day efficiency |
| D. | one of the above |
| Answer» B. tray losses | |
| 39. |
The power transformer is a constant |
| A. | oltage device |
| B. | urrent device |
| C. | ower device |
| D. | ain flux device |
| Answer» E. | |
| 40. |
The noise resulting from vibrations of laminations set by magnetic forces, is termed as |
| A. | agnetostriction |
| B. | oo |
| C. | um |
| D. | oom |
| Answer» D. oom | |
| 41. |
Power transformers are designed to have maximum efficiency at |
| A. | early full load |
| B. | 0% full load |
| C. | 0% full load |
| D. | o load |
| Answer» B. 0% full load | |
| 42. |
A transformer can have regulation closer to zero |
| A. | n full-load |
| B. | n overload |
| C. | n leading power factor |
| D. | n zero power factor |
| Answer» D. n zero power factor | |
| 43. |
For a transformer, operating at constant load current, maximum efficiency will occur at |
| A. | .8 leading power factor |
| B. | .8 lagging power factor |
| C. | ero power factor |
| D. | nity power factor |
| Answer» E. | |
| 44. |
The efficiency of two identical transformers under load conditions can be determined by |
| A. | hort-circuit test |
| B. | ack-to-back test |
| C. | pen circuit test |
| D. | ny of the above |
| Answer» C. pen circuit test | |
| 45. |
The no load current in a transformer lags behind the applied voltage by an angle of about |
| A. | 80° |
| B. | 20° |
| C. | 0° |
| D. | 5° |
| Answer» E. | |
| 46. |
The thickness of laminations used in a transformer is usually |
| A. | .4 mm to 0.5 mm |
| B. | mm to 5 mm |
| C. | 4 mm to 15 mm |
| D. | 5 mm to 40 mm |
| Answer» B. mm to 5 mm | |
| 47. |
The degree of mechanical vibrations produced by the laminations of a transformer depends on |
| A. | ightness of clamping |
| B. | auge of laminations |
| C. | ize of laminations |
| D. | ll of the above |
| Answer» E. | |
| 48. |
The transformer oil should have _____ volatility and _____ viscosity. |
| A. | ow,low |
| B. | igh,high |
| C. | ow,high |
| D. | igh,low |
| Answer» B. igh,high | |
| 49. |
If a transformer is switched on to a voltage more than the rated voltage |
| A. | ts power factor will deteriorate |
| B. | ts power factor will increase |
| C. | ts power factor will remain unaffected |
| D. | ts power factor will be zero |
| Answer» B. ts power factor will increase | |
| 50. |
Minimum voltage regulation occurs when the power factor of the load is |
| A. | nity |
| B. | agging |
| C. | eading |
| D. | ero |
| Answer» D. ero | |