How does an induction cooktop heat a pan?

An induction cooktop heats the pan directly rather than heating its own surface. Electricity runs through a coil beneath the glass, creating a magnetic field that changes direction very fast. That field induces electric currents in the base of a suitable pan, and the metal resists those currents, which produces heat. The heat then cooks the food. [1] [2]

Under the ceramic-glass plate sit coils of wire, typically copper. According to [canarymedia.com](https://www.canarymedia.com/articles/electrification/how-do-induction-stoves-actually-work), household alternating current in the U.S. reverses 60 times per second, but power electronics in an induction stove make it cycle 20,000 times or more per second. The Swiss Federal Office of Public Health describes a medium-frequency current of 20 to 100 kilohertz. Both accounts say this produces a magnetic field alternating at the same rate. The field passes through the glass ceramic almost unimpeded and reaches the pan. [3] [4]

The changing field induces circular currents, called eddy currents, in the pan base. These currents meet resistance in the metal, and that resistance dissipates energy as heat. [ingenia.org.uk](https://www.ingenia.org.uk/articles/how-do-induction-hobs-work/) credits the underlying principle of induction to Michael Faraday. The Swiss fact sheet adds that, because of the high frequency, the current flows mainly in the outer layers of the pan base, which raises current density and speeds heating. In magnetic pan bases, the field also repeatedly magnetises the metal, and this contributes further heat through what are called hysteresis losses. [5] [4] [3]

Pans made of ferromagnetic materials, such as cast iron and some stainless steels, heat well. Ingenia notes that a magnet sticking to the pan is an easy test. It also says copper pans do not heat because copper conducts electricity too well, while NOVA says aluminum pans are not heated directly. A commercial-cooktop guide says nonmagnetic vessels can be used on a ferromagnetic disk that acts as a conventional hotplate. [1] [5] [6]

The glass surface is not heated by the coil, so it stays relatively cool, though a hot pan will warm it by contact and it cools slowly after the pan is removed. The Swiss fact sheet lists fast response, rapid boiling and a lower risk of burns from the hob, but notes that hot food and oil still pose risks. Ingenia reports that induction hobs can bring water to the boil in half the time of a gas hob. [5] [4] [6]