"George Herold"
OK first this is a bit hand-wavy (I'm not doing all the math). The
eddy currents will depend on the strength of the B field in the
material (along with other things.) As long as the B field is low
enough such that it doesn't saturate the iron then the B field in iron
will be bigger than in copper. And that 'wins' over the conductivity
difference. It's for a similar reason that iron has a shorter skin
depth than copper. And a 1/16" sheet of steel is better at shielding
EM fields than a 1/16" sheet of copper.
** IOW, iron & steel absorb magnetic energy while most other metals let it
pass it right through.
Hi Phil, Well if we restrict the discussion to changing B fields and
not static ones. Then there is a reduction of the B field in any
metal. I'm not sure if it's 'more correct' to think about the B field
being absorbed, or just reflected by the conductor. For the non-
existent 'perfect' conductor, the changing B field sets up currents on
the surface and that looks like a reflection (no absorption or
transmission).
Accounts for the greater damping effect on an EM source that is within
coupling effect distance.
Beware - non simple math.
Yeah, if you want to ask what happens in iron/ steel, I'll throw up my
hands and call in an engineer, domains, hysterisis, saturation.
George H.