What is the purpose of a halogen light bulb?
Halogen light bulbs are used because:
- they can be operated at a higher temperature than can be used
for ordinary light bulbs.
This results in less heat production compared to light output
and an overall much higher efficiency in the conversion of the
energy which is input - electrical energy - to the energy which is
output as visible light.
- they have a significantly longer useful life than ordinary
incandescent light bulbs.
The invention of halogen lamps was based on the discovery of a
special physical feature: when small amounts of a halogen gas were
added to the contents of the light bulb, these were found to help
to return large quantities of evaporated tungsten atoms back to the
filament. This resulted in a significantly longer lifetime of such
General note about how all incandescent filament light bulbs
An electrical current travelling through the filament of a light
bulb makes it glow white-hot and generate both light and heat
because of the electrical resistance of the filament.
The filament is normally mounted within a special mixture of
noble and/or inert gases held inside the glass enclosure of the
light bulb, held at a pressure which is close to a vacuum.
The special mixture of gases prevents the filament from
oxidizing and burning away, which would happen extremely quickly if
it glowed white-hot in normal air which contains oxygen.