Volume I chapter 14 in DC says that permeability is the, "measure of a material's acceptance of magnetic flux". Wikipedia says about the same thing, "the degree of magnetization of a material in response to a magnetic field". The AAC book goes on to say, "greater permeability means easier passage of magnetic flux". That's the part I don't understand. If a conductive material is becoming magnetized in response to a magnetic field doesn't that mean that less of the field is getting out and more is being retained? I understand permeability to be a bad thing in a wire because the electrons will be magnetizing the line in front of them as they are moving making it more difficult for them to travel. So low permeability will mean less opposition to current (relative permeability of iron is 5000 while copper is only .999, http://en.wikipedia.org/wiki/Permeability_(electromagnetism)) Low permeability means the material is not retaining the magnetization of the field allowing the current to move more easily. So if greater permeability mean easier passage of magnetic flux and the magnetic fields are escaping the wire more easily providing less opposition than why do materials with low permeability allow more current which seems analogous to 'one of' the equations for characteristic impedance sqrt of permeability/permittivity. As permeability goes up impedance goes up, limiting the current. What I would expect with the conductive material retaining the magnetic field providing opposition. It seems that less permeability would mean easier passage of magnetic flux out of the material with less being retained to impede current flow.