Question

derive drift velocity

Answer 1

Dreift velocity is the velocity attained by any particle such as electron when kept in an electric field

(i) When conductor is subjected to an electric field E, each electron experience a force.
F=-eE
and acquires an acceleration
a = F/m = - eE/m -----(i)
Here m = mass of election, e = charge, E = electric field.
The average time difference between two consecutive collisions is known as relaxation time of election.

Answer 2

Drift Velocity of Free Electrons

When a potential difference is applied across the ends of a conductor, the free electrons in it move with an average velocity opposite to direction of electric field. which is called drift velocity of free electrons.

Drift velocity vd = eEτ / m = eVτ / ml

where, τ = relaxation time, e = charge on electron,

E = electric field intensity, 1 = length of the conductor,

V = potential difference across the ends of the conductor

m = mass of electron.

Relation between electric current and drift velocity is given by

vd = I / An e