State microscopic form of Ohms' law.

Explanation

(i) The microscopic form of ohm's law is `J= sigmaE` where `sigma` is the electrical conductivity, E the electrical field and K is current density.
(ii) This form of ohm's law operates on a microscopic level relating the current density J to the conductivity `sigma` and the electric field E.
(iii) Current I=A nevd, A is the are of of class section n the no density of `e^(-)s,` e is the charge n the charge on each electron and `v_(d)` the drift velocity of electrons.
Currejt density `J=(1)/(A)=(n e Av_(d))/(A)`
`J= nev_(d)`
Drift density `v_(d)=(eE)/(m)tau`
`tau`= average relaxation time, m-mass of the charged particle.
`I= nAe((eE)/(m)*tau)=(nAe^(2)Etau)/(m)`
`(I)/(A)=( "ne"^(2)E tau)/(m) i.e, J=(1)/(rho).E` (resistivity `rho=(m)/("ne"^(2)tau))`
`(1)/(rho)= sigma rArr J= sigma E`