Question

Explain the term 'drift velocity' of electrons in a conductor. Hence obtain the expression for the current through a conductor in terms of 'drift velocity'.

Answer 1

in the absence of electric field a free electron suffers collision with heavy fixed ions and after collision it emerges with same speed but in random direction this speed is called drift velocity .

if we consider N free electrons with velocity of i electron (I=1,2,3,4,5,6) at a given cross section then

average velocity or drift velocity= -eE\m× relaxation time

where relaxation time is the average time between successive collision

I is the current that is equal to neAVd×Time

where A is area of cross section