2. A transformer can have regulation closer to zero
Correct : C. on leading power factor
3. A transformer transforms
Correct : D. power
4. Which of the following is not the standard voltage for power supply in India ?
Correct : D. 122 kV
5. Reduction in core losses and increase in permeability are obtained with transformer
employing
Correct : A. core built-up of laminations of cold rolled grain oriented steel
6. In a power or distribution transformer about 10 per cent end turns are heavily insulated
Correct : A. to withstand the high voltage drop due to line surge produced by the shunting capacitance of the end turns
7. For given applied voltage, with the increase in frequency of the applied voltage
Correct : C. eddy current loss will remain unchanged
8. Losses which occur in rotating electric machines and do not occur in trans formers
are
Correct : A. friction and windage losses
9. In a given transformer for a given applied voltage, losses which remain constant
irrespective of load changes are
Correct : A. hysteresis and eddy current losses
10. Which of the following statements regarding an idel single-phase transformer having a turn ratio of 1 : 2 and drawing a current of 10 A from 200 V A.C. supply is incorrect ?
Correct : D. Its secondary current is 20 A
11. The secondary of a current transformer is always short-circuited under operating
conditions because it
Correct : A. avoids core saturation and high voltage induction
12. In a transformer the resistance between its primary and secondary should be
Correct : D. infinity
13. A good voltage regulation of a transformer means
Correct : A. output voltage fluctuation from no load to full load is least
14. For a transformer, operating at constant load current, maximum efficiency will occur at
Correct : D. unity power factor
15. Which of the following protection is normally not provided on small distribution
transformers ?
Correct : B. Buchholz relay
16. Which of the following acts as a protection against high voltage surges due to lightning and switching ?
Correct : A. Horn gaps
17. The efficiency of two identical transformers under load conditions can be
determined by
Correct : B. back-to-back test
18. Which of the following insulating materials can withstand the highest temperature
safely ?
Correct : C. Mica
19. Which of the following parts of a transformer is visible from outside ?
Correct : A. Bushings
20. The noise produced by a transformer is termed as
Correct : B. hum
21. Which of the following loss in a transformer is zero even at full load ?
Correct : B. Friction loss
22. Which of the following is the most likely source of harmonics in a transformer ?
Correct : D. Core saturation
23. If a transformer is continuously operated the maximum temperature rise will occur
in
Correct : B. windings
24. The hum in a transformer is mainly attributed to
Correct : C. magnetostriction
25. The maximum load that a power transformer can carry is limited by its
Correct : C. voltage ratio
26. The efficiency of a transformer, under heavy loads, is comparatively low because
Correct : A. copper loss becomes high in proportion to the output
27. An open-circuit test on a transformer is conducted primarily to measure
Correct : C. core loss
28. A no-load test is performed on a transformer to determine
Correct : D. magnetising current and loss
29. The voltage transformation ratio of a transformer is equal to the ratio of
Correct : C. secondary induced e.m.f. to primary induced e.m.f.
30. Part of the transformer which is most subject to damage from overheating is
Correct : C. winding insulation
31. If a transformer is switched on to a voltage more than the rated voltage
Correct : A. its power factor will deteriorate
32. Auto-transformer makes effective saving on copper and copper losses, when its
transformation ratio is
Correct : A. approximately equal to one
33. Minimum voltage regulation occurs when the power factor of the load is
Correct : C. leading
34. In a step-down transformer, there is a change of 15 A in the load current. This results
in change of supply current of
Correct : A. less than 15 A
35. The efficiencies of transformers compared with that of electric motors of the same
power are