structural:scholar_edition, information:extraction, structural:reformatting, structural:expansion
The H-field

The magnetic H field is defined:

H ≡ 1 μ 0 B − M {\displaystyle \mathbf {H} \equiv {\frac {1}{\mu _{0}}}\mathbf {B} -\mathbf {M} }

where μ 0 {\displaystyle \mu _{0}} is the vacuum permeability, and M is the magnetization vector. In a vacuum, B and H are proportional to each other. Inside a material they are different (see H and B inside and outside magnetic materials). The SI unit of the H -field is the ampere per metre (A/m), and the CGS unit is the oersted (Oe).