Heating of Steel via Induction of Eddy Current Skin Effect Intermolecular Friction
The heater coil is likely operating at 60 Hz which is the frequency of the power grid in USA. If it operated at higher frequency, such as 400 Hz, the same heating could be accomplished with less current, smaller components (including wire gauge), etc.
Microwaves and higher frequencies allow heating like this to be done from greater distances.
https://en.wikipedia.org/wiki/Induction_heating
Mechanism of Induction Heating
When high-frequency alternating current flows through the coil, it generates a magnetic field which induces eddy currents on the surface of the metal. The eddy currents generate heating via dielectric heating / intermolecular spinning (causing friction) and/or the metal’s resistive impedance; this is sometimes called Joule heating. Skin effect causes high-frequency energies to concentrate on the surface and thus superheat metals from their outside-in.