Question

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

Answer 1

Suppose the length of R₁ = 20Ω resistance wire is I, its area of cross-section is,4 and its resistivity is ρ Then,

When length becomes twice (2l), then its area of cross-section will become half (A/2). The new resistance