Give reasons for the following .1 .An electric bulb are usually filled innective gase of nitrogen and argon
Answers
It is used for a couple of reasons.
First of all, if there was a NON-inert gas - especially oxygen - then the filament would burn up - converting tungesten into tungesten oxide. This is why a bulb that has the glass cracked but the filament unbroken will work for a second or so as the filament burns itself up with oxygen.
BUT
We use inert gas instead of a vacuum for a couple of reasons, first of all, it can help to reduce bulb blackening from evaporated tungsten - which occurs more easily in a vacuum than with a pressure equal to around 0.7 bar (or very roughly 10 psi).
Secondly, depending on the gas (amazingly even hydrogen can be used providing these is no trace of oxygen), the filament can be run at a hotter temperature for the same life giving more efficiency (krypton etc). Alas krypton is an expensive gas and so argon is more commonly used - though with not quite the same efficiency due to a lower filament temp.
Lastly, a bulb (especially a physically large one) needs to be stronger to withstand the vacuum AND if it breaks, can be a hazard if you are nearby. The fragments of glass can implode, sweep around the back of the lamp (especially reflector style) and then come out the other side at considerable speed, ready to hit you.
So, for a few reason, we use an inert gas at just a little less than atmospheric pressure (usually). Some lamps actually are pressurised to very high levels - eg: arc lights etc.
First of all, if there was a NON-inert gas - especially oxygen - then the filament would burn up - converting tungesten into tungesten oxide. This is why a bulb that has the glass cracked but the filament unbroken will work for a second or so as the filament burns itself up with oxygen.
BUT
We use inert gas instead of a vacuum for a couple of reasons, first of all, it can help to reduce bulb blackening from evaporated tungsten - which occurs more easily in a vacuum than with a pressure equal to around 0.7 bar (or very roughly 10 psi).
Secondly, depending on the gas (amazingly even hydrogen can be used providing these is no trace of oxygen), the filament can be run at a hotter temperature for the same life giving more efficiency (krypton etc). Alas krypton is an expensive gas and so argon is more commonly used - though with not quite the same efficiency due to a lower filament temp.
Lastly, a bulb (especially a physically large one) needs to be stronger to withstand the vacuum