Question

derive an expression for drift velocity of free electrons.

Answer 1

According to drift velocity expression, relaxation time is the time interval between successive collisions of an electron on increasing temperature, theelectrons move faster and more collisions occur quickly.

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