The differential form of Ampere's Law in a vacuum correlates the curl of the magnetic field with the current density. In a magnetized material, the current density is the sum of the free and bound current densities. The free current arises due to the motion of free electrons within the material, while the bound current arises due to the alignment of magnetic dipole moments. So, Ampere's Law is modified in a magnetized material to incorporate the bound and free current densities. The bound volume current density is the curl of the magnetization. Rearranging the terms involving the curl function, the equation for free current is obtained. The magnetic field over vacuum permeability minus the magnetization is defined as the magnetic field intensity, H. So, Ampere's Law in matter states that the curl of H equals the free current density. In integral form, the line integral of H along an Amperian loop equals the net free current passing through the loop. The magnetic field intensity in magnetostatics is analogous to the displacement vector in electrostatics.