UPSC Prelims 1998 · General Studies

Question 108: Science and Technology

A fuse is used in main electric supply as a safety device. Which one of the following statements about the fuse is correct?

aIt is connected in parallel with the main switch

bIt is made mainly from silver alloys

cIt must have a low melting point

dIt must have a very high resistance

AnswerThe answer is (c).

A fuse is a short length of wire made of an alloy with a low melting point, such as tin and lead, connected in series with the circuit. When the current exceeds the safe limit, the wire heats up and melts, breaking the circuit. It is not in parallel with the switch, not made of silver alloys, and a very high resistance would waste power and not help.

Why each option is right or wrong

(a) A fuse is connected in series, not in parallel.
(b) Fuse wire is usually a tin-lead alloy, not silver.
(c) Right: it must melt easily when the current is too high.
(d) A very high resistance would waste power in normal use; what matters is the low melting point.

Explanation: written by UPSC Grade, not by UPSC.

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Source: UPSC, Civil Services (Preliminary) Examination 1998, General Studies. UPSC's own paper isn't online; the words are from a published compilation. The paper on upsc.gov.in.