Question

A wire of length l and resistance r is stretched so that its length is doubled how will the number a resistance in number be resistivity change

Answer 1

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 and area of cross-section A/2

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i.e., resistance becomes four times

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