Question

If a copper wire is stretched to make it $0.1\%$ longer, the percentage increase in resistance will be

• A. 0.2
• B. 2
• C. 1
• D. 0.1

Answer 1

The correct option is A 0.2

In case of streching $R\propto l^2$ So $\frac{\Delta R}{R}=2\frac{\Delta l}{l}=2\times 0.1=0.2$