Question

The length of the resistance wire is increased by 10%. What is the corresponding change in the resistance of wire?

• A. 10%
• B. 25%
• C. 21%
• D. 9%

Answer 1

The correct option is C 21%

If volume and density remains same, then resistance of wire:
$R\propto l^2$
where l is length of the wire
$\therefore R^{\prime }={(1+\frac{10}{100}l)}^2={\left(\frac{11}{10}\right)}^{2}R$
Hence, $\frac{R^{\prime }-R}{R}=\frac{21}{100}=21$
Therefore, change in resistance of wire = 21%