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MCQ of Transformer page-5


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41. In a transformer, the magnitude of the mutual flux is

a) High at low loads and low at high loads
b) Low at low loads and low at high loads
c) Varies at low loads and constant at high loads
d) Same at all loads

Ans: (d)

42. Use of higher flux density in trans-former design

a) Increases the weight per kW
b) Increases the weight per kVA
c) Decreases the weight per kVA
d) Decreases the weight per kW

Ans: (c)

43. The efficiency of transformer compared with that of electric motors of the same rating is

a) About the same
b) Much higher
c) Much smaller
d) Slightly higher

Ans: (b)

44. The no load current taken by a transformer lags the applied voltage approximately by

a) 60°
b) 45°
c) 30°
d) 80°

Ans: (d)

45. An ideal transformer is one which

a) Has core of stainless steel
b) Has no losses and magnetic leakage
c) Has a common core for its primary and secondary windings
d) Has inter leaved primary and secondary windings

Ans: (b)

46. In a two winding transformer, the primary and the secondary induced emfs E1 and E2 are always

a) In phase with each other
b) Antiphase with each other
c) Of different frequency
d) Equal in magnitude

Ans: (a)

47. Distribution transformers are designed to have maximum efficiency at about

a) Full load
b) No load
c) 50% of full load
d) 75% of full load

Ans: (c)

48. Use of silicon steel for laminations in a transformer reduces

a) Eddy current losses
b) Hysteresis losses
c) Both eddy current and hysteresis losses
d) Noise generated in the transformer

Ans: (b)

49. Special silicon steel is used for the laminations of transformer, because it has

a) High resistivity and high hysteresis loss
b) High resistivity and low hysteresis loss
c) Low resistivity and high hysteresis loss
d) Low resistivity and low hysteresis loss

Ans: (b)

50. The commercial efficiency of a transformer while on open circuit is

a) Zero
b) 100%
c) 50%
d) None of these

Ans: (a)


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