RadioBanter - View Single Post - Is magnetic field affected by metal conductor?

wrote:
Hi,
Is magnetic field affected by metal conductor?
How metal works with electric field, magnetic field, and
electromagnetic field?
Thanks,
SP

Metals get involved with magnetic fields in two possible ways. All
metals (and anything else with a finite conductivity) circulate
current as any magnetic field passing through it changes strength.
The circulating current creates a mirror image magnetic field that
partially cancels the one trying to penetrate the metal. For any non
superconducting metal, this process also consumes energy from the
field. These circulating currents are referred to as eddy currents.

Ferromagnetic metals (ones that are attracted to a magnet) also have
another effect. They act as a short cut for any magnetic field that
lasts long enough for the above effect to fade out, at least for field
strengths below their saturation limit. In other words, it takes more
work to create a given flux in air than it does to create the same
flux through iron. Since any effect that causes the total amount of
flux to increase, generates a force in the direction of motion that
allows the increase, this short cut effect is what causes iron to be
attracted to a magnet. The work the magnet can do in attracting the
iron is the work it took to build the field in air minus the lesser
work it takes to build that field through iron.

Things get more complicated for electromagnetic waves. Both the
electric field and magnetic field components of waves move surface
charges around as they pass by or reflect off of conductors.
Maxwell's equations are the most compact description that covers all
these possibilities.

That's enough hand waving for now. My arms are tired. ;-)