Electrical Machine - I (3140913) MCQs

MCQs of Transformers

Showing 61 to 70 out of 155 Questions
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61.
Which of the following machine will have maximum efficiency?
(a) Power Transformer
(b) Power Generator
(c) DC Motor
(d) Induction Motor
Answer:

Option (a)

62.
A transformer has comparatively much higher efficiency than a similar AC machine due to
(a) Small air gaps
(b) No moving parts
(c) Strong coupling
(d) All of the mentioned
Answer:

Option (d)

63.
Stray losses in transformer occur in
(a) Steel core
(b) Winding conductors and steel structures of transformer
(c) Transformer insulating oil
(d) Paper insulation in transformers
Answer:

Option (b)

64.
If operating a 400 Hz transformer at 50 Hz?
(a) only voltage is reduced in the same proportion as the frequency
(b) only kVA rating is reduced in the same proportion as the frequency
(c) both voltage and kVA rating is reduced in the same proportion as the frequency
(d) none of the above
Answer:

Option (b)

65.
For constant load current at which power factor the efficiency of the transformer will be maximum?
(a) Zero power factor
(b) Unity power factor
(c) Leading power factor
(d) Lagging power factor
Answer:

Option (b)

66.
The efficiency of a transformer at a full load of 0.8 p.f. lag is 90%. Its efficiency at a full load of 0.8 p.f. lead will be?
(a) 90 %
(b) less than 90 %
(c) more than 90 %
(d) none of the above
Answer:

Option (a)

67.
Iron loss in transformer mainly occurs in
(a) Iron made tank of the transformer
(b) Steel core in a transformer
(c) Winding of transformer
(d) Transformer insulating oil
Answer:

Option (b)

68.
Which of the following losses remain constant during normal operation of transformer?
(a) Copper loss
(b) Core loss
(c) Stray loss
(d) All losses in transformer vary with load
Answer:

Option (b)

69.
What will be the eddy current loss if the supply frequency of a transformer becomes double?
(a) Eight times
(b) Four times
(c) Doubled
(d) Remains the same
Answer:

Option (b)

70.
What will be the hysteresis loss if the supply frequency of a transformer becomes double?
(a) Eight times
(b) Four times
(c) Doubled
(d) Remains the same
Answer:

Option (c)

Showing 61 to 70 out of 155 Questions
4 5 6 7 8 9