Question

Two different wires X and Y of same diameter but different materials are joined in series across a battery. If the number density of electrons in X is twice that in Y, find the ratio of drift velocity of electrons in the two wires.

Answer 1

Drift velocity,

V_d = \(\frac{I}{neA}\) 

= \(\frac{I}{n(nd^2/4)e}\)

i.e., V_d ∝ \(\frac{1}{n}\) 

Since the wires are connected in series, 

Current I through both is same.

Given, 

n_x = 2n_y

∴ \(\frac{(v_d)x}{(v_d)y}\) = \(\frac{n_y}{n_x}\) = \(\frac{1}{2}\)