Question

Why is inert gas filled in electric bulb ?

Hint:

Remember the two main reasons for using inert gas: 1. To prevent the filament from burning out (oxidation) which would happen in air. 2. To reduce the evaporation (sublimation) of the filament which would happen in a vacuum. Both effects extend the bulb's life.

Answer 1

An inert gas, such as argon or nitrogen, is filled in an incandescent electric bulb to increase its lifespan and efficiency.
\begin{enumerate} \item Function of the Filament: The bulb produces light when its filament, made of tungsten, is heated to a very high temperature (around 2500\(^\circ\)C) by the electric current.
\item Problem with Vacuum: If the bulb were a vacuum, the hot tungsten filament would evaporate (a process called sublimation) at these high temperatures. This would thin the filament, causing it to break quickly, and also deposit a black layer on the inside of the glass, reducing the light output.
\item Problem with Air: If the bulb were filled with air, the oxygen in the air would cause the hot tungsten filament to oxidize rapidly and burn out almost instantly.
\item Solution with Inert Gas: To overcome these problems, the bulb is filled with a chemically unreactive (inert) gas. The pressure of the inert gas suppresses the evaporation of the tungsten filament, allowing it to be heated to a higher temperature for brighter light and significantly increasing its operational life.
\end{enumerate}