TRABEM wrote:

What's the relative permeability of air??

"Relative permeability" is the permeability relative to that of free
space. The relative permeability of any non-magnetic material, including
air, is 1.


They give this statement on the help page, but I don't understand what
it means.

Note: µ0 = 4¶·10-7 [Hm-1] (Absolute Permeability)

The permeability of free space (µ0) is 4 * pi * 10^-7 webers/amp-m (MKSA
units). The permeability (µ) of anything is its relative permeability
(µr) times µ0.

Roy Lewallen, W7EL