Question

A wire of resistance 10$\Omega$ is elongated by 10%. The resistance of the elongated wire is

• A. 11$\Omega$
• B. 11.1$\Omega$
• C. 12.1$\Omega$
• D. 13.1$\Omega$

Answer 1

The correct option is C 12.1$\Omega$

Let the length (initial) be L

The final length $=1.1L$

$\because$ V is constant

$\Rightarrow L_1{A}_1=L_2{A}_2$

$\frac{L_1}{1.1L_1}=\frac{A_2}{A_1}$

$\frac{R_1}{R_2}=\left(\frac{L_1}{L_2}\right)\left(\frac{A_2}{A_1}\right)$

$=\frac{1}{1.1}\times \frac{1}{1.1}$

$\frac{10}{R_2}=\frac{1}{1.21}$

$R_2=12.1\Omega$