MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY MARTYN F. CHILLMAID / SCIENCE PHOTO LIBRARY
Light bulb. Light bulb switched on and glowing. The light comes from the filament, a fine tungsten wire which heats up and glows as an electric current is passed through it. Tungsten is an ideal material for a filament as it is strong and has a high melting point (3410 degrees celsius). The interior of the bulb contains an inert gas, usually a mixture of nitrogen and argon. This is to exclude oxygen which would cause corrosion of the tungsten. Whilst in use, the tungsten filament gradually evaporates away until it breaks.
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