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NEET 2017 · Ohm's Law, Resistivity & Temperature

Ohm's Law, Resistivity & Temperature question from NEET 2017

Q53NEET 2017Easy

Ohm's Law, Resistivity & Temperature

The resistance of a wire is 'R' ohm. If it is melted and stretched to 'n' times its original length. its new resistance will be

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Answer: (b)

Volume is constant: $Al = A'l'$ , so $l' = nl \Rightarrow A' = A/n$ .
$R' = \dfrac{\rho (nl)}{A/n} = n^2 \dfrac{\rho l}{A}$
$R' = n^2 R$
So the answer is (b) $n^2 R$ .

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