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Question
Why an electric bulb needs to be vacuumed? Can we light up a bulb in the
space without enclosing in the glass bulb?
Asked by:
Muhammad Nasir
Answer
An incandescent light bulb contains a thin wire filament (usually tungsten) that glows hot
when an electric current is run through it. In the presence of oxygen, the filament would
burn up as a result of the high temperature. A glass bulb, then, is used to keep oxygen
away from the filament.
While a vacuum will work, any inert gas that inhibits combustion will also work. Since
the vacuum of space would have no oxygen, a bare filament WOULD work as a light bulb
without the glass globe.
By the way, even without oxygen present a filament eventually deteriorates as its atoms
dissipate. The presence of a halogen gas actually inhibits this deterioration, allowing
higher filament temperatures and brighter light bulbs. So the glass globe can also help
enhance a bulb's capability.
More info on light bulbs:
Light bulb image by Adrienne Hart-Davis
Tungsten filament close-up image by Dr. Howell at PSU, Material Science Dept.
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Answered by:
Paul Walorski, B.A., Part-time Physics Instructor
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