JEE Mains · Physics · STD 12 - 3. current electricity
A copper wire is stretched to make it \(0.5\%\) longer. The percentage change in its electric resistance if its volume remains unchanged is ................ \(\%\)
- A \(2\)
- B \(2.5\)
- C \(1\)
- D \(0.5\)
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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