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