Question

Why is Tungsten used almost exclusively for filament of electrical lamps?

Answer 1

Hint The electric lamps glow at extremely high temperatures. Tungsten is a strong metal having a very high melting point and they are heat resistant as they do not burn readily at high temperatures, thus acting as insulators when used for any such purpose.


Complete step-by-step answer
Electrical heating is used to produce light in bulbs. The filament inside the bulb must retain as much as heat possible in order to get very hot, so that it can emit light and not melt at high temperatures.
For this, a strong metal with high melting point is used so that the filament should remain thermally protected and isolated as much as possible. Pure Tungsten is one such element used for making bulb filament as it has the highest melting point of 3695K. Also, its vapour pressure is very low and has great tensile strength out of all the metals used to conduct heat and electricity.
The chemical symbol of Tungsten is W which comes from Wolfram. It is a grey-white shiny metal, which is solid at room temperature. It has excellent corrosion resistivity and is least affected by most mineral acids, thus it is chemically non-reactive. It does not melt even when a large amount of heat is produced due to current passing through the filament.
One of the important reasons why it is used in bulb filaments is that it is a metal and has a characteristic property of being drawn into wires, called ductility. This makes it very suitable for this purpose along with its resistance to withstand high temperatures.

Note Although it has tremendous use, yet it has a limitation. Its hardness makes it more brittle and breakable. On smashing or hitting against anything hard, it might shatter or crack. The broken tungsten cannot be repaired further. Also, it is a heavy metal.