Ohm's law

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, one arrives at the usual mathematical equation that describes this relationship: 

 I = V/R where I is the current through the conductor in units of amperes, V is the voltage measured across the conductor in units of volts, and R is the resistance of the conductor in units of ohms.

From Ohm’s Law,

I α V

Or I = K.V where constant of proportionality K is known as conductance of a conductor whose unit is Mho. As conductance is reciprocal of resistance we can write conductance = 1/resistance

i.e. K = 1/R

therefore, From Ohm’s Law we can write I = V.1/R = V/R

or V= IR