[Ohm's law](https://en.wikipedia.org/wiki/Ohm%27s_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?