A filament is a thin wire used in incandescent light bulbs to produce light. It is typically made of tungsten , a material resistant to high temperatures. When electricity flows through the filament, it becomes so hot that it begins to glow, resulting in the emission of light.
How does a filament work?
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Heating by current : When an electric current is passed through the filament, the filament begins to heat up due to the resistance of the material. Tungsten can withstand very high temperatures without melting.
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Annealing : Once the filament heats up sufficiently (usually between 2500–3000°C), it visibly glows and produces light. This process is the basis of how a traditional incandescent bulb works.
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Gas in the lamp : Many incandescent bulbs use an inert gas (such as argon) or even a vacuum around the filament to protect it from oxidation. In vacuum-filled incandescent bulbs, the filament heats up more quickly, but in gas-filled bulbs, the filament corrodes less quickly and remains capable of producing light longer.
Characteristics of a filament:
- High temperature : The filament must become extremely hot to produce light, which means a significant amount of energy is lost in the form of heat.
- Energy inefficiency : Incandescent bulbs are less energy efficient compared to other light sources like LEDs or fluorescent lamps . Most of the energy is converted into heat, not light.
- Lifespan : The lifespan of an incandescent bulb is relatively short because the filament wears out over time due to the high temperatures. This makes incandescent bulbs less durable compared to modern lighting technologies.
Applications of the filament:
- Traditional incandescent bulbs : This is the most common application of the incandescent filament. It was used in household lighting until incandescent bulbs were increasingly replaced by more energy-efficient options like LEDs.
- Flash and Specialty Lighting : Filament filament can also be used in applications where a temporary, very bright light source is required, such as in flash lamps or some scientific equipment.
Although filament technology is now less used due to inefficiency and the advent of more energy-efficient lighting such as LED and halogen lamps , it was the basis for lighting in most homes throughout the 20th century.