Ohm’s law is valid___________.

Hint: We have to understand the concept of the ohm’s law such that the definition should be explained by us and the mathematical formula and also the characteristics of the Ohm’s law. We have to find out the validation of the ohm's law with the help of its characteristics in the conductor.

Complete answer:
Ohm’s law is stated as: The law states that the flow of current in the circuit is directly proportional to the potential across the conductor and inversely proportional to the resistance of the conductor. Mathematically, ohm’s law is stated as:
\[V\alpha I\] Or \[I\alpha V\]
And \[I\alpha \dfrac{1}{R}\]
\[V = IR\]

Now, we have to show the validation of ohm’s law as: It is said that the resistance is directly proportional to length of the conductor and inversely proportional to the area of that conductor. When we remove the sign of proportionality, a constant will be introduced into the equation and that constant is called the resistivity of the material. The resistivity depends on the type of material and is supposed to be constant.

But later it was accepted that the resistivity of the conductor depends on temperature thus the resistivity changes with temperature and it turns out to be that the resistance also changes when resistivity changes with temperature. So, the conclusion of this result is that the ohm’s law is proven wrong and the resistance which was considered as constant turns out to be variable.That is why, we have to keep temperature constant to obtain ohm’s law correctly by keeping resistance constant.

Hence, ohm’s law is valid only when temperature is constant.

Note:We have observed that according to the experiments performed by the researchers the result is obtained that the resistance is dependent on resistivity and resistivity is variable at variable temperature, to keep resistance constant we have to consider resistivity as constant and to keep resistivity constant we have to keep temperature constant. Hence the ohm’s law is said to be valid at constant temperature only.