Induction Cooker

An induction cooker uses a type of induction heating for cooking. It is chiefly distinguished from other common forms of stovetop cooking by the fact that the heat is generated directly in the cooking vessel, as opposed to being generated in the stovetop (as by electrical coils or burning gas) and then transferred to the cooking vessel.

In an induction stovetop, a coil of copper wire--an electromagnet--is placed underneath the cooking pot. An oscillating current is applied to that coil, which produces an oscillating magnetic field. That magnetic field creates heat in the cooking vessel over it, in two different ways. First, it induces a current in the electrically conductive pot, which produces Joule (I2R) heat. Second, it also creates magnetic hysteresis losses in the ferromagnetic pot. The first effect dominates: hysteresis losses typically account for less than ten percent of the total heat generated.

Induction cookers are faster and more energy-efficient than traditional electric cooktops; moreover, they allow instantaneous control of cooking energy, which no energy source other than gas offers. Because induction heats the cooking vessel itself, the possibility of burn injury is significantly reduced compared to other methods: only skin contact with the cooking vessel itself (or, when high heat has been used, the stovetop for a while after the vessel has been removed) can cause harm. There are not the high temperatures of flames or red-hot electric heating elements found in traditional cooking equipment, which generates heat independent of the cooking vessel. Further, induction cookers do not themselves warm the surrounding air, resulting in further energy efficiencies.

It is possible to build an induction cooker that works with any conductive pot, even if the pot is not ferromagnetic (for example, an aluminum or copper pot). But the increased permeability of an iron or steel pot makes the system substantially more practical, by increasing the inductance seen at the drive coil and by decreasing the skin depth of the current in the pot, which increases the AC resistance for the I2R heating. [2] Most practical induction cookers are designed for ferromagnetic pots; consumers are advised that the cooker will work only with pots that a magnet will stick to. Moreover, it is not at all possible to build an induction cooker that would work with a cooking vessel made of an electrically insulating material (for example, a glass or ceramic pot).

Since heat is being generated from an induced electric current, the unit can detect whether cookware is present (or whether its contents have boiled out) by monitoring the voltage drop caused by resistance in the circuit (which reflects how much energy 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.

Induction heating could be considered to have reached mainstream status in the USA when in 2008 Consumer Reports reviewed induction appliances alongside gas and thermal heating. (The induction units outscored the other types.)