A light bulb is a device for using electricity to make light. The electricity flows through a wire called a filament. The filament gets so hot that it glows and gives out light.

When the circuit is switched on the electricity flows through the filament, making it hot enough to glow brightly. The wire in the filament is in the form of a coil. This allows a long length of wire to be packed into a small space. This is done because a long length of wire gives out more light than a short length.

The gas in the light bulb is called argon. It is used instead of air because argon will not cause the hot filament to burn up. A light bulb in the home may last for 1000 hours.

There are two kinds of ways a light bulb can be connected into a circuit. The light bulb used in most British homes has a bayonet fitting. The 'torch' light bulbs used with batteries have a screw fitting. Light bulbs used in North America and Europe mainly have Edison Screw fittings. The first light bulbs were designed in the same year by rivals Swan and Edison. This is what their first successful bulbs looked like.