We may describe the behaviour of electric and magnetic fields, and through the following differential equations, where
and are constants,
where the electric displacement is given in terms of the electric
, is the dielectric
constant, with a vacuum
the charge density.
The magnetic induction (often referred to as the magnetic
field) is related to the magnetic field through
. is the magnetic permeability with a vacuum value
Finally, the electric current is related to the electric
field through Ohm's law
where is the electrical conductivity.
We have already seen that (3.3) implies that there are no
sources of magnetic field (no magnetic monopoles) and flux tubes have
a constant strength.
Prof. Alan Hood