Question

If the length of a conductor is increased by 20% and cross-sectional area is decreased by 4% , then calculate the percentage change in the resistance of the conductor.

Answer 1

$R=\frac{Pl}{A}$
$R'=\frac{P\ 1.2\ l}{0.96A}=\frac{1.25\ pl}{A}$
R' = 1.25 R

So, the percentage change in resistance is 25%