Ohm's Law is a mathematical law that takes several different forms, depending on application. While we will discuss other forms later, we will start with the form of primary mathematical interest.
We can use Ohm's law to relate the average current density to the electric field, by using a constant quantity of the conductor, known as the conductivity:
Ohm's law can be stated as:
where j is the current density (current per unit area), σ is the conductivity and E is the electric field.
Each different type of conductor will have a unique constant conductivity, which can typically be determined through experimentation.