George Simon Ohm stated the Ohm’s law. He stated that the electric current flowing through a wire will be directly proportional to the potential difference across the ends when the temperature remains constant. That constant is the resistance. V = I RLimitations1. Ohm’s law is applicable and valid for many materials. But there are some materials that do not support the ohm’s law. Some materials and devices which are used in electric circuits do not have the proportionality between voltage and current.2. Although Ohm’s law is an important principle in the field of electronics, it cannot be considered as an actual physical law. We know that as per ohm’s law voltage / current = a constant and that constant is the resistance. But the resistance does not remain constant all the time. When the current passes through a material, it heats up. When the temperature of the material changes, the resistance changes. So when the resistance changes, and we divide the voltage across the resistor by the current passing through it, we will not get the same numbers always.