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

For spherical wire,
`R prop l^(2)`
`(DeltaR)/R = (2Deltal)/l`
`rArr (DeltaR)/R = 2 xx 0.1 = 0.2 %`