UPSC Civil Services Model Paper 4

In a bulb, when current passes through the filament, it produces light and heat both.
Metals like tungsten (which are used as filament) glowing brightly may oxidize at high temperatures if normal gases are filled inside the bulb.
Filling of inert gases like nitrogen and argon prevents oxidation of the filament and increase its life. So, statement is 2 is correct.
Inert gases do not play any other role like increasing power efficiency, illumination, changing heat profile of the filament, etc. So, statements 1, 3, and 4are NOT correct.
They may reduce the heat emitted by the bulb to some extent as the bulb's inside is properly insulated.