The current I is related to the surface integral of the current density J by

			(1)
			(2)

(3)

with the conductivity and E the electric field. If is constant, then

(4)

Now, for a wire, E and are constant and perpendicular, so

(5)

where A is the cross sectional area, V is the voltage, and L is the length of the wire. Plugging in gives

(6)

Defining the resistance

(7)

and solving for V gives Ohm's law,

(8)

Current, Ohm's Phase Law, Resistance, Voltage