JEE Mains · Physics · STD 12 - Current electricity
- JEE Mains 2019
- Medium
- Numerical
A copper wire is stretched to make it \(0.5\%\) longer. The percentage change in its electric resistance if its volume remains unchanged is ................ \(\%\)
Pick an option to check your answer.
Answer & Solution
Correct Answer
(C) \(1\)
Step-by-step Solution
Detailed explanation
\( \mathrm{R} =\frac{\rho \ell}{\mathrm{A}} \)
\( \mathrm{R} =\frac{\rho \ell^{2}}{\mathrm{A} \ell}=\frac{\rho \ell^{2}}{\mathrm{V}}\)
\(\frac{\mathrm{d} \mathrm{R}}{\mathrm{R}}=\frac{2 \mathrm{d} \ell}{\ell} \)
\({\rm{ Hence, }}\frac{{{\rm{dR}}}}{{\rm{R}}}{\rm{ }} = 1\% \)
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