How Do Incandescent Lamps Work?

Incandescent bulbs were the first type of light bulb invented. They are still some of the cheapest and most widely-used bulbs on the market. The concept behind their function is simple.

Function

Incandescent light bulbs produce light when their filament is supplied with an electrical current that heats them up to several thousand degrees Fahrenheit.

Filament

The first versions of incandescent light bulbs utilized carbon filaments. Modern incandescent light bulbs utilize tungsten filaments, because out of all known metals, tungsten has the highest melting point, making it ideal for withstanding extreme temperatures.

Light Output

The light output of a light source is measured in lumens. Incandescent light bulbs are some of the most inefficient light bulbs on the market but they are still capable of producing a respectable 8 to 21 lumens per watt of power drawn.

Fill Gas

The earliest versions of incandescent light bulbs contained a vacuum, because air causes a bulb's filament to oxidize at high temperatures. Later, it was discovered that using inert fill gases like argon or a nitrogen-argon mixture will slow the evaporation of filaments.

Burn Out

Incandescent bulbs typically only last for around 750 hours. Tungsten filaments evaporate slowly and unevenly throughout the life of the bulb. Parts of the filament become thinner than other parts of the filament, which often results in the filament eventually snapping, melting or breaking and therefore being unable to illuminate.

References

• The Great Internet Light Bulb Book, Part 1:Incandescent Including Halogen Light Bulbs
• Mineral Information Institute: Tungsten