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MCQ of Transformer page-16


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51. A transformer has copper loss of 1.5 % and reactance of 3.5 % when tested on load. It will have better regulation at

A) 0.8 lagging p.f.
B) 0.8 leading p.f.
C) Unity power factor
D) None of the above.

Ans : (B)

52. If full load copper loss of a transformer is 800 W, its copper loss at 75% load will be

A) 200 W
B) 400 W
C) 450 W
D) 800 W

Ans : (C)

53. If the ohmic resistance of windings of a transformer is zero, then

A) transformation ratio will be infinity
B) core loss will be more than copper loss
C) copper loss will be zero
D) there will be maximum magnetic leakage.

Ans : (C)

54. In a transformer, the resistance between the primary and secondary must be

A) Infinity
B) 100 kΩ
C) 1 kΩ
D) Zero.

Ans : (A)

55. The negative voltage regulation of a transformer is possible only with

A) Resistance load
B) Inductive load
C) Capacitive load
D) Any load.

Ans : (C)

56. Positive voltage regulation is an indication of …………… load.

A) Resistive
B) Either inductive or resistive
C) Capacitive
D) Inductive.

Ans : (B)

57. When a transformer operates under no load conditions, the current

A) will be in phase with the applied voltage
B) will lead the applied voltage by about 90°
C) will lag the applied voltage by about 90°
D) will lag the applied voltage by.

Ans : (D)

58. In a step up transformer, the emf per turn on primary winding is

A) in the same ratio with emf on secondary winding as the voltage ratio
B) less than the emf per turn of winding on secondary side
C) more than the emf per turn of winding on secondary side
D) the same as emf per turn of winding on secondary winding.

Ans : (D)

59. The useful flux of a transformer is 1.2 weber. When the transformer is loaded at 0.8 p.f. lagging, the mutual flux will be closer to

A) 1.1 weber
B) 1.2 weber
C) 1.28 weber
D) 1.5 weber.

Ans : (A)

60. A 230/2300 V transformer takes no load current of 5 A at 0.25 power factor lagging. The core loss is

A) 192.5 W
B) 287.5 W
C) 212.6 W
D) 300.2 W.

Ans : (B)


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