Electricity: Magnetic and Heating Effects - Heating Effect of Electric Current

When an electric current flows through a wire, the wire gets hot. This is known as the heating effect of electric current.

The amount of heat produced in a wire depends on its material, length, and thickness. For example, wires used for making electric circuits do not normally become hot, whereas elements of heating appliances do.

Heating appliances like electric irons, heaters, and toasters contain a coil of wire called an 'element'. When current flows through the element, it becomes red hot and gives out heat.

The filament of an electric bulb (usually made of tungsten) gets heated to such a high temperature that it starts glowing and emitting light.

An electric fuse is a safety device based on the heating effect of current. It contains a wire made of a special material that melts quickly and breaks the circuit if the current exceeds a safe limit ($I > I_{limit}$).

The heat produced ($H$) in a conductor is directly proportional to the square of the current ($I^2$), the resistance of the conductor ($R$), and the time ($t$) for which the current flows. This is known as Joule's Law of Heating.