Question

The drift velocity of free electrons in a conductor is Vd, when the current is flowing in it. If both the radius and current are doubled,
the drift velocity will be
(A) Vd/8
(B)Vd/4
(C)Vd/2
(D) Vd​

Answer 1

Explanation:

• According to the question, the radius and the current is doubled

we know, drift velocity is equals to,

Vd = I / e. n. a

a = πR^2

implies,

Vd = 2I / π(2R) ^2 .e. n

Vd = 2I / 4πR^2 .e. n

implies,

Vd = I / 2πR^2 .e. n

therefore,

Vd = I / 2e. n. a

therefore the drift velocity is reduced to half.