Ohm's law states that the current through a conductor between two points is directly proportional to the voltage across the two points. Introducing the constant of proportionality, the resistance, R one arrives at the usual mathematical equation that describes this relationship:
$$V=IR.$$
Then why the assertion that V=IR is a statement of Ohm's law is not true?
Best Answer
$V = RI$ is a statement of Ohm's law, provided the resistance $R$ is a constant, i.e. independent of the voltage $V$ or the current $I$. Ohm's law is valid to a good accuracy for a wide range of materials (called ohmic materials), but does not apply to all materials.