Question 193: Current Electricity

Question

The resistance of a wire is 5 $$\Omega$$. It's new resistance in ohm if stretched to 5 times of it's original length will be :

Accepted Answer

$$
\mathrm{R}_{	ext {initial }}=\frac{ho \ell}{A}=5 \Omega
$$
$\because$ Volume of wire is constant in stretching
$$
\begin{aligned}
& \mathrm{V}_{\mathrm{i}}=\mathrm{V}_{\mathrm{f}} \\
& \mathrm{A}_{\mathrm{i}} \ell_{\mathrm{i}}=\mathrm{A}_{\mathrm{f}} \ell_{\mathrm{f}} \\
& \mathrm{A} \ell=\mathrm{A}^{\prime}(5 \ell) \\
& \mathrm{A}^{\prime}=\frac{\mathrm{A}}{5} \\
& \mathrm{R}_{\mathrm{f}}=\frac{ho \ell_{\mathrm{f}}}{\mathrm{A}_{\mathrm{f}}}=\frac{ho(5 \ell)}{\left(\frac{\mathrm{A}}{5}ight)} \\
& =25\left(\frac{ho \ell}{\mathrm{A}}ight) \\
& =25 	imes 5=125 \Omega
\end{aligned}
$$

Answer

25

Answer

625

Answer

5

Answer

125

Current Electricity

The resistance of a wire is 5 $\Omega$. It's new resistance in ohm if stretched to 5 times of it's original length will be :

Choose the correct answer: