Hõõgniit

Hõõgniit, also known as a filament, is a crucial component in incandescent light bulbs. It is a thin wire, typically made of tungsten, that heats up and emits light when an electric current passes through it. The resistance of the filament causes it to become very hot, reaching temperatures of around 2,700 degrees Celsius (4,892 degrees Fahrenheit). This intense heat causes the filament to glow, producing visible light through a process called incandescence.

The choice of tungsten for the filament is due to its exceptionally high melting point and tensile strength, which allows it to withstand the extreme temperatures required for light emission without melting or breaking. The filament is usually coiled to increase its length within a small space, thereby increasing its resistance and light output. Early incandescent bulbs used carbon filaments, but tungsten proved to be more durable and efficient.

To prevent the hot filament from oxidizing and burning out quickly, it is enclosed in a glass bulb from which the air has been removed or replaced with an inert gas like argon or nitrogen. This inert atmosphere significantly extends the lifespan of the filament. Despite their widespread use, incandescent bulbs are relatively inefficient, with a large portion of the energy consumed being converted into heat rather than light. This has led to their gradual replacement by more energy-efficient lighting technologies such as LEDs and CFLs.