Incandescent light bulbs
An incandescent light bulb , is an electric bulb which produces light with a filament wire heated to a high temperature by electric current that is passing through it, until it glows .
The hot filament is protected from oxidation with a glass envelope that is filled with inert gas .The inert gas may be nitrogen or argon ( which are widely used ) or also krypton or xenon .
The first successful light bulb filament were made up of carbon . But they had a negative coefficient of resistance - as they got hotter , their resistance is decreased . Now they use tungsten metal for filament .But we can observe that the bulb gets blackened.
The evaporated tungsten eventually condenses on the inner surface of glass envelope , darkening it . When a filling of inert gas is used , the evaporated tungsten deposits preferably in the uppermost part of glass envelope , blackening just that portion of envelope.
An incandescent light bulb , is an electric bulb which produces light with a filament wire heated to a high temperature by electric current that is passing through it, until it glows .
The hot filament is protected from oxidation with a glass envelope that is filled with inert gas .The inert gas may be nitrogen or argon ( which are widely used ) or also krypton or xenon .
The first successful light bulb filament were made up of carbon . But they had a negative coefficient of resistance - as they got hotter , their resistance is decreased . Now they use tungsten metal for filament .But we can observe that the bulb gets blackened.
The evaporated tungsten eventually condenses on the inner surface of glass envelope , darkening it . When a filling of inert gas is used , the evaporated tungsten deposits preferably in the uppermost part of glass envelope , blackening just that portion of envelope.
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