UPSC Prelims 1996 · General Studies

Question 121: Science and Technology

Assertion (A): Transformer is useful for stepping up or stepping down voltages. Reason (R): Transformer is a device used in D.C. circuits. In the context of the above two statements, which one of the following is correct?

aBoth A and R are true and R is the correct explanation of A.

bBoth A and R are true but R is not a correct explanation of A.

cA is true but R is false.

dA is false but R is true.

AnswerThe answer is (c).

A is true: a transformer steps alternating voltage up or down using mutual induction between two coils. R is false: it works only on alternating current, because a changing magnetic flux is needed to induce a voltage in the second coil, and steady DC gives none. Remember: transformer - AC only.

A. A transformer steps AC voltage up or down.
R. It works only with alternating current, not DC.

How you could have got this

If you were sure statement 1 is correct, (d) goes. Then judge the second statement; if it is correct too, decide whether it explains the first.

This follows an unofficial answer: UPSC has not published its key for this year, and if that answer is wrong, so is this path.

Which options go is worked out from UPSC’s key and the options, not by a model.

Why each option is right or wrong

(a) R is false, since transformers do not work on DC.
(b) R is false, so this fails.
(c) Right: A is true, R is false.
(d) A is true, so this fails.

Explanation: written by UPSC Grade, not by UPSC.

Practise this paper timedPrevious question Next question

Source: UPSC, Civil Services (Preliminary) Examination 1996, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.