441. Part of the transformer which is most subject to damage from overheating is_____________?
A. iron core
B. copper winding
C. winding insulation
D. frame or case
E. transformer tank

442. Open circuit test on transformers is conducted to determine____________?
A. hysteresis losses
B. copper losses
C. core losses
D. eddy current losses

443. If a transformer is switched on to a voltage more than the rated voltage______________?
A. its power factor will deteriorate
B. its power factor will increase
C. its power factor will remain unaffected
D. its power factor will be zero

444. Short circuit test on transformers is conducted to determine____________?
A. hysteresis losses
B. copper losses
C. core losses
D. eddy current losses

445. Auto-transformer makes effective saving on copper and copper losses, when its transformation ratio is_________________?
A. approximately equal to one
B. less than one
C. great than one
D. none of the above

446. Minimum voltage regulation occurs when the power factor of the load is_____________?
A. unity
B. lagging
C. leading
D. zero

447. For the parallel operation of single phase transformers it is necessary that they should have___________?
A. same efficiency
B. same polarity
C. same kVA rating
D. same number of turns on the secondary side.

448. In a step-down transformer, there is a change of 15 A in the load current. This results in change of supply current of_________________?
A. less than 15 A
B. more than 15 A
C. 15 A
D. none of the above

449. The transformer oil should have _______ volatility and _______ viscosity?
A. low,low
B. high,high
C. low,high
D. high,low

450. The efficiencies of transformers compared with that of electric motors of the same power are____________?
A. about the same
B. much smaller
C. much higher
D. somewhat smaller
E. none of the above

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