Question

a wire of given material having length l and area of cross section A has a resistance of 10 ohm.What would be the resistance of another wire of the same material having length l/4 and a area of cross section 2.5A?

Answer 1

This is the formula,
$r = \frac{p \: l}{a}$
10 = p × L/ A

R = p × L÷4 / 2.5 A
R = p × L / 4 × 2.5 A
R = p × L / 10 A
10 × 10 = p × L / A
p × L / A = 100

So , new resistance = 100 ohms