Question

A piece of wire of resistance 20ohm is drawn out so that its length is increased to twice to its original length.Calculate the resistance of the wire in the new situation.

Answer 1

R= 20 ohm
R= rho L/ A (old wire)

For new wire,
R= rho 2l/ A/2
( Since length is doubled,so area would become half)
Therefore, R= rho 4l/A
So, R(new) = 4*20 = 80 ohm ( since, R= rho L/ A which is 20)