My picture below shows a coil carrying AC current, generating an alternating magnetic field. On top of the coil I've drawn a disk of high-permeability metal. Such as carbon steel, or mu-metal.
- If the disk is made of carbon steel, the oscillating magnetic field induces eddy currents which, thanks to the metal's high permeability, are "concentrated" in a thin layer close to the bottom, which is perfect for heat generation; it's an induction cooker.
- But if the disk is made of mu-metal, the field high permeability of the material provides a "tighter" path for the magnetic field, and decreases the strength of the magnetic field beyond it, but without inducing currents, eddy currents, or an opposing magnetic field; it's a magnetic shield.
Mu-metal and carbon steel have many different material properties. Please can someone help me understand what the relevant differences are, and exactly how this results in such different behaviour? Thanks!