85. An auto-transformer having a transformation ratio of 0.8 supplies a load of 10 kW. The power transforred inductively from the primary to the secondary is
A. 10 kW
B. 8 kW
C. 2 kW
D. zero

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86. The secondary of a current transformer is always short circuited under operating conditions because
A. it protects the primary circuits
B. it is safe to human beings
C. it avoids core saturation voltage induction
D. none of the above

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87. While conducting short-circuit test on a transformer the following side is short-circuited
A. HN. side
B. L.V. side
C. primary side
D. none of the above

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88. What is a typical use of an auto transformer?
A. Isolating transformer
B. Toy transformer
C. Control Transformer
D. Variable transformer

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89. The insulating properties of transformer oil are adversely affected by the presence of
A. oxygen
B. copper
C. moisture
D. ozone

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90. The core section of large transformer can work in parallel with another transformer which may be 1. Star ? Star 2. Delta ? Delta 3. Star ? Delta 4. Delta ? Star Of these the correct answer are
A. 1 and 2
B. 3 and 4
C. 1 and 4
D. 2 and 3

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91. An auto-transformer is preferred in cases where
A. load is fluctuating
B. power factor is varying
C. ratio of transformation is low
D. ratio of transformation is high

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