Induction cooker is a modern electric cooker which works on the principle of electromagnetic induction to heat cookware. Induction heating comprised of three basic factors: electromagnetic induction, the skin effect and the conversion of electrical energy into thermal energy.
In an induction cooker a large coil of copper is mounted underneath the cooking surface of the induction cooker, when it is connected through AC supply an AC current is established through the mounted coil this current produces a time varying magnetic field and if a secondary coil is placed in the region of time varying magnetic field a voltage will get induced in it. This phenomenon is called as electromagnetic induction. While cooking on induction cooker the cookware used works as the secondary coil and thus a voltage gets induced in it, which generates a current termed as eddy current. This current flows through the cookware and encounters resistance in its movement due to which its energy gets transformed into heat energy. The rate of heating depends upon frequency of the induced current (this frequency depends upon how rapidly the magnetic field is changing), intensity of the induced current, the specific heat (ability to absorb heat) of the material used in cookware, the magnetic permeability of the material and the resistance to the flow of current.
Since the induction is based on magnetic principle the cookware used must be compatible with induction heating. In order to make it compatible with induction heating the cookwares are either made up of ferromagnetic material or it should contain a thin layer of ferromagnetic material at its base. Ferromagnetic materials are those substances which when placed in magnetic field strongly get magnetised. The ease of magnetisation is characterised by a quantity called permeability. Also higher the value of permeability more the current gets confined to the surface of the material. The depth in a material through which current flows is characterised by the skin depth. The current, which is the directional movement of electrons, will face more hindrance in its flow if it is confined to a smaller skin depth and thus the resistance will further increase and more will be transformation of energy into heat.
The ferromagnetic Martials like stainless steel, cast iron possess these properties and widely used in induction cookware. On the other hand non ferromagnetic materials like aluminium or copper cookwares are more conductive, they have low value of permeability, large value of skin depth and current flows through a thicker layer and thus encounter less resistance to its flow. The easiest way to check whether your cookware is compatible with an induction cooker is to take a magnet and try to stick to the bottom of the cookware if it sticks the cookware is compatible with induction cooker.
