Induction cooking: why ferromagnetic pan?

Question

In the image above, we have the principle of induction cooking. An alternating current is run through the coil, which causes a change in flux. This change in flux induces eddy currents in the conductive pan, and by Joule heating/resistive heating (P=VI), this causes the pan to heat up.

So the only thing that you need is a pan that can conduct electricity/the eddy currents right? As long as the pan does not have a too low or a too high resistance.

However, why is the effect specifically optimal for ferromagnetic materials/conductors? How does the ability to magnetize somehow enhance the effect of induction heating? Does the magnetization of the pan itself somehow enhance the eddy currents or something?

Answer 1

Ferromagnetic material is needed for the same reason that transformers working with low frequency alternating current (a.c.) need iron cores. The magnetic field generated by coils in the cooker's hob are supplemented by magnetic fields due to alignment by this field of magnetic domains in the iron. The resulting magnetic flux density may be hundreds of times larger than if there were no iron. Thus as the field changes, because it is a.c. that is passed through the coils, the changes are far greater than if there were no iron, and a much larger voltage is generated. Hence the heating effect is greater, despite the greater resistivity of the iron compared with that of (say) copper or aluminium.