Question

define drift velocity write the expression for the current in a conductor of cross sectional area a in terms of drift velocity

Answer 1

From the quantizations of charges we know

Q= ne

n= number of electrons

e= charge

Also, I= Q/t

then I= ne/t 

Answer 2

The velocity gained by moving the electrons inside the conductor in a uniform electric field is the drift velocity. The expression for the same is I=nAev

Let the length of conductor be = l

Let the cross sectional area be =  A.

Let number of free electrons per unit volume be = n.

Let the drift velocity of electrons be = v

Thus, the total number of electrons will be -  

Number of free electrons in a piece of conductor = nAl (number of free electrons per unit volume × volume)

Total charge due to the free electrons = q  = nAle

Time taken by the charge to traverse the conductor fully = t = l/v

Thus, the current in the conductor -

I =q/t

= nAle/(l/v)

= nAev