If *V* is the potential difference across the ends of any conductor, then current *I* will flow through it. The value of the current changes with changes in potential difference. German scientist simen ohm found out that:

The value of current I passing through a conductor is directly proportional to the potential difference V appalled across its ends, provided the temperature and the physical state of the conductor does not change.

If a graph is drawn between *V* and *I*, it will be a straight line (fig. 16.5 which represents the direct proportional relation between *V* and *I* i.e.,

Where *R* is the constant of proportionality the value of which can be determined from *V-I* graph. The value of *R* is different for different conductors.

**Limitations of ohms law**

Ohms law is applicable only in case of metallic conductors when their temperature and physical state do not change.

Fig. 16.5