Q21 of 37 Page 1

Derive the expression for drift velocity of free electron in terms of relaxation time and electric field applied across a conductor.

When conductor is subjected to an electric field E, each electron experiences a force.
F=-eE
and acquires an acceleration
a = F/m = - eE/m ________ (1)
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.

_____________ (2)


As v=u + at (from equation of motion)


The drift velocity v is defined as




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