d

I_{enc} =

**H ⋅ dl**
Ampere's Circuital Law is an important law of magnetostatics that enables one to easily calculate the magnetic field generated by a current flowing through a wire.

Normally, to apply this law, we imagine a circle around a wire(s), having a radius equal to that at which we wish to determine the magnetic field. Here I_{enc} is the net current passing through the interior of that circle, **dl** is part of the path the circle makes and **H** is the magnetic field intensity upon that circle. We then take the dot product of **H · dl** and integrate around the closed loop our circle forms, thus giving us an equation from which we can easily calculate the value of **H**.

This is also the basis for one of Maxwell's Equations.