Mathematics in Physics

JEE Main level, single correct, medium

118 of 121

Question 118 of 121

If a wire is stretched to make it 0.1%0.1 \% longer, its resistance will :

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Answer: (A) increase by 0.2%0.2 \%

R∝ℓ2\mathrm{R} \propto \ell^2 (for a given volume)
⇒ΔRR%=2Δℓℓ%\Rightarrow \frac{\Delta \mathrm{R}}{\mathrm{R}} \%=\frac{2 \Delta \ell}{\ell} \%
Thus when wire is stretched by 0.1%0.1 \% resistance increases by 0.2%0.2 \%

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