Question

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 :

• A. $\frac{R}{n}$
• B. $n^2 R$
• C. $\frac{R}{n^2}$
• D. $nR$

Answer 1

Answer: (B)

$n^2 R$

Answer 2

$\frac{R_{2}}{R_{1}} =\frac{l_{2}^{2}}{l_{1}^{2}}$
$=\frac{n^{2} l_{1}^{2}}{l_{1}^{2}}$
$\frac{R_{2}}{R_{1}} =n^{2}$
$R_{2} =n^{2} R_{1}$