**Ampere's Law**, named for Andre-Marie Ampere, relates electric current to magnetic fields, and is one of Maxwell's Equations. It is often used in the calculation of the magnetic field at a point due to one or many current-carrying wires. It is the magnetic analogue to Gauss's Law, and can be stated in integral form as

where is magnetic field, *C* is a closed curve, is current enclosed by *C*, and is the permeability of free space.

In differential form, Ampere's Law is written

where is current density.