Ohm's law can be deducaed from the relation I = nAev

where I is the current, n is the no. of free electrons per unit volume of the conductorf, A is the area of cross section of the conductor, e is the electronic charge and v is the drift velocity of the free electron

substituting for v in the equation,

we get

which shows that

since is a constant. **Hence Ohm's law.**

.

Resistance

Resistivity