JEE Mains · Physics · STD 12 - 3. current electricity
The length of a metallic wire is increased by \(20 \%\) and its area of cross section is reduced by \(4 \%\). The percentage change in resistance of the metallic wire is \(.......\)
- A \(24\)
- B \(23\)
- C \(22\)
- D \(25\)
Answer & Solution
Correct Answer
(D) \(25\)
Step-by-step Solution
Detailed explanation
\(R =\rho \frac{\ell}{ A }\) be the initial resistance new resistance \(R ^{\prime}=\rho \frac{1.2 \ell}{0.96 A }=1.25 \rho \frac{\ell}{ A }=1.25 R\) \(\text { percentage change }=\frac{1.25 R - R }{ R } \times 100=25 \%\)
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