Incandescent lamps produce light through the electric heating of a wire (the filament) at a high temperature, emitting radiation within the visible field of the spectrum.
The main parts of an incandescent lamp are the filament, the filament supports, the glass bulb, the filling gas and the base. Filament: The one used in modern lamps is made out of wolfram (high fusion point and low evaporation degree). A higher luminous efficiency would be achieved by twisting the filament as an spiral.
Glass bulb: It is a cover of sealed glass which encloses the filament and avoids contact with the air outside (so that it does not burn).
Filling gas: Filament evaporation is reduced filling the glass bulb with an inert gas. The most commonly used gases are argon and nitrogen. In these lamps, luminous energy obtained is very little compared to the heat energy irradiated, that is to say, a great amount of the transformed electric energy is lost as heat and its luminous efficacy is small (it is a waste- energy lamp). The advantage of these lamps is that they are directly connected to the electric current without the need of an auxiliary
equipment for their working.