Ohmís  Law



        Suppose that a potential difference ( V ) is applied between the ends of a device.


        A current ( i ) will pass through the device.


        If the current ( i ) is linearly dependent on the potential difference ( V ) irrespective of the polarity or magnitude of V, then the device is said to obey Ohmsí law ( Ohmic device ) { figure 27-11 b }.


        If the relation between i and V is not linear, then the device is non-ohmic, it does not obey Ohmsí law { figure 27-11 c }.


       In summary, for conducting devices and wires, we can write Ohmís law as :        V = i R      or       E = r J