5
where Bm is the field contributed by the material core It turns out that
this additional field Bm is proportional to the magnetisation M of the
material and is expressed as
Bm = m0M
(5 10)
where m0 is the same constant (permittivity of vacuum) that appears in
Biot-Savart’s law It is convenient to introduce another vector field H, called the magnetic
intensity, which is defined by
0
–
µ
H= B
M
(5