Electromagnetic damping and conductivity of metals

[maltesers]

The following data shows the conductivity of 5 metals and the rate of change in gravitational potential energy due to induced current when the metal is passed through a electromagnetic field of 5.4mT on the end of a pendulum. you know, the classic eddy current experiment.
I'm just wondering if anyone knew an equation linking the conductivity and rate of energy disipation? It looks like an exponential relationship to me. Anyone know exactly what it is? Would be really helpful! cheers

Material Rate of change in Gravitational conductivity
potential energy(10^-4J/s) (10^6 siemens/m)

Steel 3.53 1.5
Nickel silver 3.62 3.5
Zinc 3.71 17
Aluminium 4.47 35
Copper 8.46 58

 

[maltesers]

sorry that table didnt come out properly

 

[lightgrav]

conductivity is a MATERIAL property, while PE is an OBJECT property.
IF each material was made into an object of the same dimensions (l,w,h)
AND were moved through the magnet at the same speed,
THEN then power dissipated by macroscopic electromagnetic phenomena
should be proportional to (magnetic mu)^2 (electrical conductivity).

I'd guess your data includes a lot of microscopic EM phenomena (friction).