Question

The filament of an electric bulb is made of:
A. Carbon
B. Aluminium
C. Tungsten
D. Nickel

Answer 1

Hint: In this question, we know that the filaments are heated up to a temperature of ${2500^ \circ }C - {3000^ \circ }C$ so as to reach the rated lumens. And the melting point of Tungsten is generally ${3422^ \circ }C$ hence, it can easily withstand the expected operating temperature and the expansion associated with it. Therefore filament of an electric bulb is made of tungsten.

Complete Step-by-Step solution:
To be precise we know that the filament of any bulb will have to withstand a very high operating temperature and it also has to go through high expansion during heating and contraction during cooling. And as tungsten has a high melting point and very good tensile strength, it is being used in the filaments of an electric light bulb.
Light in and the electric bulb is produced when the filament is heated to incandescence point that is the point where light starts to emit when the temperature of a material is raised by the flow of electric current through it. When a metal is heated the point where the electromagnetic radiation starts to emit with the wavelength of the radiation in the range of the visible spectrum that is 390nm to 700nm can also be called as incandescence point and this provides us the light.
If we look at the Filament type lamps that are CFL, Tube Lights, Incandescent Bulbs, Halogen Lamp, Sodium Vapor Lamps, etc. Here the filaments are heated up to a temperature of ${2500^ \circ }C - {3000^ \circ }C$ so as to reach the rated lumens. Accordingly, the filament needs to withstand this higher temperature. The melting point of Tungsten is generally ${3422^ \circ }C$ hence, it can easily withstand the expected operating temperature.
Before the tungsten people were using carbon filaments. But Carbon can sublime and because of this sublimation, the glass bulb was used to get coated with soot after some time and therefore reducing the effective light. This problem is now avoided in tungsten filament.
So the correct option is C.

Note: For these types of question we need to know about some famous metals and their uses like tungsten, constantan, manganin, aluminium, etc. we also need to know about their application, for example, manganin and constantan are used for standardizing instruments, Tungsten is used in filaments, aluminium used for lightweight structure, Copper for current-carrying wires, etc.