Electric Bulb
Convert electric energy into light energy. It is a transducer. When electricity passed through its filament, It starts to glow. Works on Law of conservation of energy.
We will discuss two main components
- Working of Tungsten Filament.
- Why we use Inert gas
When electricity flows into the bulb, it heats the tungsten wire filament. The filament gets so hot that it glows with white light. Light bulbs that use this method to generate light with heat are called Incandescent (جلتی ہوی ) lights..
Tungsten Filament
A filament is a metal wire that glows when electricity is passed through it. A metal must be heated to extreme temperatures before it will emit a useful amount of visible light. Most metals will actually melt before reaching such extreme temperatures.
- Pure tungsten has some amazing properties highest melting point.
It can reach high temperature before melting. An electric current can heat the filament around 2000-3300 K, which stays below the melting point of tungsten. Tungsten bulb are energy inefficient when it is used for light source only. They radiate heat energy also.They are still in use, why?
Inert / Noble Gas
The filament in a light bulb is housed in a sealed, oxygen-free chamber to prevent combustion. All the air was sucked out of the bulb to create a near vacuum.
At such extreme temperatures, the occasional tungsten atom vibrates enough to detach from the atoms around it and flies into the air. In a vacuum bulb, free tungsten atoms shoot out in a straight line and collect on the inside of the glass. As more and more atoms evaporate, the filament starts to disintegrate, and the glass starts to get darker. This reduces the life of the bulb considerably.
In a modern light bulb, inert gases, typically argon, greatly reduce this loss of tungsten. When a tungsten atom evaporates, chances are it will collide with an argon atom and bounce right back toward the filament, where it will rejoin the solid structure. Since inert gases normally don’t react with other elements, there is no chance of the elements combining in a combustion reaction.
