Ohm’s law : When the physical conditions such as temperature etc. remain same, the current flowing through the conductor is directly proportional to the potential difference applied across the ends of the conductor, i.e., I \\propto V or V \\propto I \\Rightarrow \\dfrac{V}{I} = constant \\Rightarrow V = IR where R is constant of proportionality and is called resistance of the wire.Necessary condition for validity of Ohm's Law is that physical condition such as temperature of the conductor remains same. "Procedure" V-I graph is a straight line passing through the origin of the graph as shown. Conclusion : Straight line nature of graph shows that the current is proportional to the potential difference. Hence, Ohm’s law verified. The slope of V-I graph gives the value of resistance of the conductor at the given temperature.