They work on the principle of electromagnetic induction, vibrating electromagnetic fields, eddy currents and dissipation of heat.
In the induction cooking system, we have a cooking stove/platform and cookware (utensils, pans). The stove contains a strong copper coil that passes AC current at high frequency. The current produces magnetic field and flux around the coil. The varying current produces varying magnetic fields (flux). So varying magnetic flux causes eddy currents in ferromagnetic materials near the coil. Eddy currents are currents flowing within the cookware in small circles and loops. Different magnetic fields and potentials result in different electric fields and potentials at different points in the material of the cookware. Hence, small loops of currents are produced. The resistance of the cookware causes very quick heating up of the cookware. These heat up much faster than regular gas based heating. This is similar to the heating up of transformer core material, we often see them on roadside.
Induction cooking system is an energy efficient cooking system. More than electric cooking or gas based. It is more environment friendly, clean, less polluting and needs less ventilation in the kitchen. It is healthier as we do not inhale gases that are emitted by burning gases. It does not heat up kitchen so people will feel comfortable. They save at least 10% of energy consumption.
These are introduced in to the market in this decade and are quite popular in advanced countries. They have a thermostat and LED display. The surface of the stove is ceramic and smooth. It does not heat up as it is not ferromagnetic. The loss of heat in the copper coil is very less. Cookware must be metallic and ferromagnetic. A ferromagnetic flat plate may be used on top of the platform, to heat non-ferro cookware through conduction. It is not efficient.
The cookware must have a flat bottom for better heating, as then the distance of cookware will be nearer to the copper coil inside. A wider flat bottom will be much better. The induction heater can detect the presence of ferromagnetic material on the platform by the amount of energy transferred. It can know the temperature of the surface in contact with the cookware. It has automatic controls to start and switch off when there is no vessel on top, of if it is not ferromagnetic. Also, if any food item spills on the surface it is much easier to clean.