Incandescent light bulb

Invented by Joseph Swan and improved by Thomas Edison in the late 19^th century, the filament light bulb is a device that produces light by heating a tungsten filament until it glows.

Principle of the incandescent light bulb

The filament resists the electrical current running through it. It therefore heats to a very high temperature (several thousand degrees) and emits light: this is incandescence. Tungsten is the material used, as it is the metal with the highest fusion point.

In order to avoid this thin filament from catching fire and being destroyed when exposed to dioxygen, it is placed in a glass bulb containing either a vacuum, or a controlled oxygen-free atmosphere. However, the filament always sublimates when used and thins until it breaks.

The filament light bulb, out of step with sustainable development

Due to their operating principle, filament light bulbs (including halogens) have very poor energy performances as lighting devices: most of the electricity is transformed into heat by the Joule effect. This is why, in the current context of sustainable energy and development, this type of light bulb is gradually being replaced by low energy consumption light bulbs.

For more information on different types of light bulbs, please read the question and answer sheet.