Question

Two conducting wires X and Y of diameter ratio 2 :1 but different materials are joined in series across a battery. If 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

In series, the current through the two wires will be same. So `I_(X) = I_(Y) or n_(x) A_(x) e v_(x)= n_(y)A_(y) ev_(y)`
or `v_(x)/v_(y) =n_(y)/n_(x) xx A_(y)/A_(x) = n_(y)/n_(x) xx (pi D_(y)^(2))/(pi D_(x)^(2)) = 1/2 xx 1/2^(2) = 1/8`