1. Electric current
A magnetic field is generated by a 240-volt, 20-to-30-amp, 20-to-75-kHz-frequency electric current from a 40- or 50-amp breaker through a copper coil.
2. Magnetic field
The magnetic field acts as a bridge, linking the electric current in the copper coils with eddy currents induced in ferromagnetic cookware.
3. Eddy currents
Magnets pull otherwise randomly distributed electrons in a consistent direction. The magnetic field sets the pan's electrons into organized motions known as eddy currents. The currents generate heat in the pan walls.
4. Joule effect
Resistance to electron flow is higher in the cookware than in copper. Increasing the resistance raises the heat, as James Prescott Joule demonstrated in 1841. The skillet, to a physicist, is merely an impedance.
The intermolecular friction and heat made by the IGBT result from a process called hysteresis. Both hysteresis and eddy currents generate heat in the cookware. Attempts to determine which process plays the more important role have been known to cause screaming arguments between induction-cooktop engineers.
Induction cooktops generate heat in the cookware itself. The processes described at right are a more efficient alternative to heating by a flame or a resistive electric coil. Ninety percent of the heat made by induction reaches the food—on an electric range, 65 to 70 percent goes to the food; for gas, it's only 40 to 55 percent.