Deduce Ohm's law using the concept of drift velocity.

Explanation

We know that the drift velocity is given by
`v_(d)=(I)/(n eA)` . . . (i)
Also `v_(d)=(eEtau)/(m)` . . (ii)
From eqs. (i) and (ii),
`(eEtau)/(m)=(I)/(n eA)`
or `(E)/(I)=(m)/(n e^(2)Atau)`
or `(V)/(lI)=(m)/(n e^(2)Atau)`
or `(V)/(I)=(ml)/(n e^(2)A tau)`
or `(V)/(I)=(ml)/(n e^(2)A tau)=R` (constant)
or `V=IR`.