Derive the relation `vec(j)=sigmavec(E)` with terms which has usual meaning.

Explanation

According to Ohm.s law V=IR
But `R= (rhoI)/(A)`
`V= I(rhol)/(A)`
`(I)/(A)=(V)/(rhol)`
But `(I)/(A)`= J called current debnsity and
`(V)/(I) = E` - Electric field
`:. J = (1)/(rho)` E
`J = rho E ( because (1)/(rho) sigma)`
`vecj=rhovecE`