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MCQ of Transformer page-15

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41. Full load copper loss in a transformer is 1600 watts. At half load, the loss will be

A) 400 W
B) 800 W
C) 1600 W
D) 6400 W.

Ans : (A)

42. The efficiency of a 430/200 V transformer at full load 0.8 p.f. lagging is 95%. The efficiency at full load 0.8 p.f. leading, will be

A) 90
B) 95 %
C) 95.5 %
D) 99 %.

Ans : (B)

43. The secondary of a current transformer is always short-circuited under operating conditions because

A) It is same for operation
B) It protects the primary circuit
C) It avoids high voltage surges
D) It avoids core saturation and high voltage induction.

Ans : (D)

44. A good voltage regulation of a transformer means

A) Output voltage fluctuation from no load to full load is least
B) Output voltage fluctuation with power factor is the least
C) Difference between primary and secondary voltage is maximum
D) Difference between primary and secondary voltage is least.

Ans : (A)

45. Auto transformer is used

A) when higher efficiency is desired
B) when the transformation ratio is small
C) when copper losses are to reduced
D) when operator is not available.

Ans : (B)

46. If the break occurs in a 200:100 volt autotransformer in the winding which is common to high voltage as well as low voltage side, then the output voltage on the low voltage side will be

A) 200 V
B) 100 V
C) 300 V
D) Zero.

Ans : (B)

47. A transformer steps up the voltage by a factor of 100. The ratio of current in the primary to that in the secondary.

A) 0.1
B) 0.01
C) 100
D) 1

Ans : (C)

48. The leakage impedance of primary and secondary winding of a transformer is (3 + j4) ohms and (1 + j4) ohms respectively. It can be concluded that the transformer has

A) Low voltage secondary
B) Low voltage primary
C) High voltage secondary
D) No conclusion can be drawn on the basis of the information given.

Ans : (A)

49. In an autotransformer, effective saving on copper and copper losses will occur, when the transformation ratio is

A) 0.707
B) Less than 1
C) More than 1
D) nearly equal to 1.

Ans : (B)

50. The colour of dry silica gel is

A) blue
B) pale green
C) pale pink
D) pale yellow.

Ans : (A)

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