D. ROBERTS / SCIENCE PHOTO LIBRARY D. ROBERTS / SCIENCE PHOTO LIBRARY
Light bulb. X-ray of an electric light bulb. Bulbs produce light from a filament (horizontal structure, upper centre). This is a finely coiled wire of tungsten which heats up and glows as an electric current is passed through it. The contacts through which the electricity is supplied are seen on the base (bottom centre) as white oval shapes. Tungsten is used in the filament as it is strong and has a high melting point (3410 degrees Celsius). The glass bulb contains inert gases, usually nitrogen and argon, to prevent corrosion of the filament by oxygen. Over its lifetime, the tungsten filament slowly evaporates away until eventually it breaks.
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