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

Options

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

Answer

B

Explanation

`l A = l(1 + 0.1//100) A'`
`A' = A(1 + 0.1//100)`
`(R')/(R) = (l')/(A') .(A)/(l) = (1 + 0.1//100)^2 = 1 + (0.2)/(100)`
`((R')/(R) -1) xx 100 = 0.2 %`.