How Does a Heating Coil Work?


Heating Coil Basics

  • A heating coil is a simple device that turns electric current into heat energy. Heating coils are used in electrical stoves and ovens, hair dryers, electric blankets, water heaters and in any other piece of electric equipment that needs to produce its own heat. A heating coil need not be coil-shaped to work. For example, the filaments in an incandescent lightbulb work like a heating coil even though it is a straight piece of wire.

How Heating Coils Create Heat

  • Electrical current is the movement of electrons through a conductor. In a good conductor, the electrons move quite freely between the molecules, wasting very little energy. In a resistor, however, the electrons collide with the molecules, wasting energy. Every time an electron collides with another molecule, some of its energy is turned into heat. Heating coils are resistors. They turn an electric current almost completely into heat.

Conduction and Convection

  • With most heating coils, the heat is carried from the coil either by conduction or convection. In conduction, the heating coil is in direct contact with the object that needs to be heated, while in convection, air or water currents carry the heat to its target. For example, an electric stove works by conduction--a pan is set on the coil and the heat flows directly into the pan. A hair dryer works by convection; a fan blows air onto the heating coil, which heats up the air. The air then carries the heat to the hair of the user.


  • Infrared heating coils work a little bit differently. All objects radiate infrared light. The hotter an object is, the more infrared light it radiates. This infrared travels through the air without heating it much, but when it reaches another solid object, it is absorbed and turned back into heat. Infrared heating coils such as those used on flattop electric stoves are insulated so that all the heat they produce is trapped inside. This heats the coil up to an extremely high temperature. The coil produces a lot of infrared light, which is absorbed by the pan above it and turned back into heat.

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