If a copper wire is stretched to make it `0.1%` longer wha is the percentage change in its resistance?

Options

A. increase by `0.2%`
B. decrease by `0.2%`
C. decrease by `0.05%`
D. increase by `0.05%`

Answer

A

Explanation

(a) Resistance of wire
`R = (rhol)/A = (rhol)^2/C (where Al = C)`
`:. Fractional chage in resistance
`(Delta R)/R = 2(Deltal)/l`
`:. Resistance will increase by 0.2 %`.