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Electrical Engineering Objective Questions { Transformers }



1. A transformer transforms
A. frequency
B. only voltage
C. only current
D. power

2. An ideal transformer is one which
A. has a common core for its primary and secondary windings
B. has no losses and magnetic leakage
C. has core of stainless steel and windings of pure copper metal
D. has interleaved primary and secondary windings

3. Coupling between the two windings of a transformer can be increased by
A. increasing the number of turns in the two windings
B. increasing the primary voltage
C. interleaving the windings on a commoncore of low reluctance
D. reducing the insulation of the two windings

4. In an ideal transformer, the no-load primary current Io
A. lags behind Vi by 900
B. is in phase with VI
C. leads Vi by 900
D. lags V1 by an angle lying between 0? and 90?

5. The primary and secondary induced emfs E1 and E2 in a two-winding transformer are always
A. equal in magnitude
B. antiphase with each other
C. in-phase with each other determined by load on transformer secondary
D.

6. Regarding the working component lw and ?magnetising component I of the noload primary current of a transformer which of the following statement is true?
A. I < I
B. Iw >w
C. I = I
D. lp/Iw = constant w

7. Transformer cores are built up from laminations rather than from solid metal so that
A. oil penetrates thecore more easily
B. eddy current loss is reduced
C. less insulation is required for the windings
D. turn ratio is higher than voltage ratio

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