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MCQ of Transformer page-13


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21. A 220 V/12 - 0 - 12 V transformer has an emf/turn of 1 V. The number of turns on secondary would be

A) 24 with centre tap
B) 24 with no centre tap
C) 220 with centre tap
D) 12 with centre tap.

Ans : (A)

22. In a step down transformer

A) Phase shift is always 180
B) Secondary current is always more than primary current
C) Secondary turns are less than primary turns
D) Secondary power is less than primary power.

Ans : (C)

23. The leakage flux in a transformer depends upon

A) load current and voltage
B) load current
C) load current, voltage frequency and power factor
D) load current, voltage and frequency.

Ans : (B)

24. A transformer has a full load iron loss of 900 W and copper loss of 1600 W. At what percent of the load, the transformer will have maximum efficiency ?

A) 50 %
B) 75 %
C) 90 %
D) 100 %.

Ans : (B)

25. Which of the following is not a routine test on transformers ?

A) Impedance test
B) Core insulation voltage test
C) Radio interference test
D) Polarity test.

Ans : (C)

26. Iron loss for transformer is 400 watts. If the transformer is working at its maximum efficiency then copper loss will be

A) 100 W
B) 200 W
C) 400 W
D) 1600 W.

Ans : (C)

27. A 1 kVA transformer, at full load, will have

A) windage losses less than copper losses
B) windage losses more than iron losses
C) iron losses greater than copper loses
D) copper losses greater than iron losses.

Ans : (D)

28. The iron core in a transformer provides path to the main flux at

A) High conducting
B) Low resistance
C) High reluctance
D) Low reluctance.

Ans : (D)

29. A transformer has full load copper loss of 800 W and core loss of 600 W. Total losses at to no load will be approximately

A) 600 W
B) 1000 W
C) 1100 W
D) 1400 W.

Ans : (A)

30. Buchholz relay is used on

A) Furnace transformer
B) Welding transformer
C) Oil cooled transformer
D) Air cooled transformer

Ans : (C)


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