For some components the current is directly proportional to the potential difference providing the temperature remains constant.These components are called Ohmic conductors as they obey Ohm's law.A graph of current against potential difference will be a straight line through the origin.For an Ohmic conductor, V ∝ I. The constant of proportionality is R the resistance.This gives V = I R or R = V/IThe gradient of an IV graph for a component that obeys Ohm's law is 1÷resistance.