An induction cooker uses induction heating for cooking. Unlike other forms of cooking, heat is generated directly in the pot or pan (cooking vessel), as opposed to being generated in the stovetop by electrical coils or burning gas. To be used on an induction cooker, a cooking vessel must be made of a ferromagnetic metal.
In an induction cooker, a coil of copper wire is placed underneath the cooking pot. An alternating electric current flows through the coil, which produces an oscillating magnetic field. This field induces an electric current in the pot. Current flowing in the metal pot produces resistive heating which heats the food. While the current is large, it is produced by a low voltage.
An induction cooker is faster and more energy-efficient than a traditional electric hob. It allows instant control of cooking energy similar to gas burners. Because induction heats the cooking vessel itself, the possibility of burn injury is significantly less than with other methods; the surface of the cook top is only heated from contact with the vessel. There are no flames or red-hot electric heating elements as found in traditional cooking equipment. The induction effect does not heat the air around the vessel, resulting in further energy efficiencies; some air is blown through the cooktop to cool the electronics, but this air emerges only a little warmer than ambient temperature.
Induced current can heat any type of metal, but the magnetic properties of a steel vessel concentrates the induced current in a thin layer near the surface, which makes the heating effect stronger. In non-magnetic materials like aluminum, the magnetic field penetrates too far, and the induced current encounters little resistance in the metal. Practical induction cookers are designed for ferromagnetic pots that will stick to a magnet.
Since heat is being generated by an induced electric current, the unit can detect whether cookware is present (or whether its contents have boiled dry) by monitoring how much power is being absorbed. That allows such functions as keeping a pot at minimal boil or automatically turning an element off when cookware is removed from it.