Question

The resistance of 100 m of copper wire is 0.01Ω. What will be the resistance of 200 m of another copper wire of half the area of cross section as above?

Answer 1

Explanation:

Resistance = resistivity × length / Area

In R1 = rho × 100 / A

0.01 = rho × 100 / A

In R2 = rho × 200 / A/ 2

R2 = rho × 400 / A

R1 / R2 = 100 / 400

R2 = 4 × R1

R2 = 4 × 0.01

R2 = 0.04 ohm

So when the area of cross section gets halved, the new resistance becomes 4 times of previous resistance.