Ohm's law states that current in an circuit is directly proportional to [[1]]

Ohm’s law states that the voltage across a conductor is directly proportional to the current flowing through it, provided all physical conditions and temperatures remain constant.

In other words, I is proportional to V. 
Mathematically:

  $$\begin{gathered} V\propto I \\ \Rightarrow V=RI \end{gathered}$$ 
We must provide a constant in order to equal this. 
The result is V = R * I. 
R is the resistance of the conductor through which the current is flowing. It is the measure of opposition to the flow of the current through the conductor. Resistance depends on the nature, length, and size of the conductor.