Question

A wire of length L and resistance R is stretched so that its length is doubled and the area of cross-section is halved. How will its:
(i) resistance change?
(ii) resistivity change?
Justify your answer in each case.

Answer 1

(i) Here, length is doubled and area of cross-section is halved. Thus, a wire of length l and area of cross-section A becomes a wire of length 2l andarea of cross-section A/2.

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i.e., resistance becomes four times

(ii) Resistivity of a substance does not depend on its length or area of cross-section. It depends on the nature of the material and temperature. Hence there is no change.