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Electrical Engineering Objective Questions { Transformers }

99. Steel used in the construction of transformer core has loss
A. low permeability and low hysteresis
B. low permeability and high hysteresis loss
C. high permeability and high-hysteresis loss
D. high permeability and low hysteresis loss.

100.  The iron losses of a transformer may be calculated by knowing the weight of
A. yokes alone
B. cores alone
C. cores and yokes
D. copper winding alone.

101.  Other things remaining the same, the efficiency of an a utotransformer compared to a two winding transformer is
A. lower
B. the same
C. higher
D.d) dependent on the load.

102.  A transformer cannot raise or lower the oltage of a D.C. supply because
A. there is no need to change the D.C. voltage
B. a D.C. circuit has more losses
C. Faraday's laws of electromagnetic induction are not valid since the rate of change of flux is zero
D. none of the above

103. Efficiency of a power transformer is of order of the
A.100 per cent
B. 98 per cent
C.50 per cent
D. 25 per cent

104. Natural oil cooling is used for transformers upto a rating of
A. 3000 kVA
B. 1000 kVA
C. 500 kVA
D. 250 kVA

105. Power transformers are designed to have maximum efficiency
A. at early full load
B. 70% full load
C. 50% full load
D. no load

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