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.
 		Light bulb by Adrienne Hart-Davis
Light bulb filament close-up


Answered by: Paul Walorski, B.A., Part-time Physics Instructor

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