Ohm's law state that the potential difference (voltage) across the ideal conductor is proportional to the current through it.
where, V = potential difference between two points which include a resistance, I =current flowing through the resistance and R=resistance (constant of proportionality ).
Limitations of Ohm's law :
1. If temperature changes, ohm's law cannot be applicable.
2. Not applicable for non - metallic conductors.
3. Not applicable for non linear devices ( diodes, zener diodes, etc.,).