If a wire is stretched to make it 0.1 % longer the percentage change in its resistance would be:

Explanation

Resistance `R = (rho l)/A" …(1)"`
`rho -` Specific resistance
Let V be the volume
` A = V/l`
Sub (2) in (1) we get,
`R = (rho l^2)/(V)`
Change in resistance is given by
`:." "(Delta R)/R = (2 Delta l)/(100)`
Here `rho` and V are constant.
` :." "(Delta R)/R xx 100 = (2Delta l)/l xx 100 `
` = 2 xx (0.1)/100 xx 100 = 0.2 `
Percentage change in resistance = 0.2.