Why is argon gas used along with tungsten wire in an electric bulb?

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To increase the life of the bulb

To reduce the consumption of electricity

To make the emitted light colored

To reduce the cost of the bulb

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Answer is Wrong!

This question was previously asked in

UPSC CDS-1 – 2018

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Argon gas is used in electric bulbs along with a tungsten filament primarily to increase the life of the bulb. At the high operating temperature of the tungsten filament, tungsten atoms tend to evaporate or sublime. The presence of an inert gas like argon at a certain pressure within the bulb reduces the rate of evaporation of the tungsten filament, making it last longer.

– Tungsten filaments operate at very high temperatures (around 2500-3000°C) to produce light by incandescence.
– High temperatures cause the tungsten metal to sublime (evaporate) from the filament.
– Evaporated tungsten atoms deposit on the cooler glass bulb wall, causing blackening.
– Sublimation thins the filament over time, eventually causing it to break.
– Inert gases like argon, krypton, or xenon, when present at pressure, impede the movement of tungsten atoms away from the filament, reducing the evaporation rate and thus prolonging the filament’s life and preventing rapid blackening of the bulb.

Early incandescent bulbs were vacuum sealed. Adding inert gas was a significant improvement in bulb technology, leading to longer-lasting and brighter bulbs compared to vacuum bulbs. While the inert gas does cause a slight loss of energy through convection, this is offset by the ability to operate the filament at a slightly higher temperature for improved efficiency and light output, while still significantly increasing bulb lifespan.

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