Question

The filament of an electric bulb is tungsten because
$A.$ its resistance is negligible
$B.$ it is cheaper
$C.$ its melting point is high
$D.$ filament is easily made

Answer 1

Hint – Here we will proceed by using the properties of incandescent light bulbs. By using the properties that why tungsten is used as the filament for incandescent light bulbs.

Complete step-by-step answer:
Common electric bulb is known as an incandescent bulb where a filament is heated to a very high temperature to emit light through a process called black body radiation. Heat is generated due to resistivity when electricity is passed through an object. A hot object constantly emits electromagnetic radiation. The wavelength of the radiation emitted depends on the temperature of the object. As the temperature of the object increases the wavelength of the radiation shortens. When the wavelength of emitted electromagnetic waves is in the range of 750 Nanometers to 400 Nanometers we get visible light. An object gets heated when electricity is passed through it if the electrical resistivity levels are high.
The reasons why Tungsten is used as the filament for incandescent light bulbs.

(a). It has a high melting point.

Incandescent light bulbs need to be at very high temperatures to operate. This means that the filament must be able to sustain high temperature and not melt. Incandescent bulbs operate at around ${3000^ \circ }C$and the melting point of tungsten is at ${3422^ \circ }C$.

(b). It has a high resistivity.

In order to heat the filament, electricity must pass through it. Higher resistivity means that the filament’s temperature can increase more easily.

(c ). It can be fashioned into wires.

Tungsten filament can be processed into filaments and thin wires which allow them to fit into bulbs.

Therefore, we can say that Tungsten has a melting point ${3380^ \circ }C$. It does not melt at high temperatures. It retains as much heat generated, so that it becomes very hot and emits light.

Note – Whenever we come up with this type of question, one must know that Incandescence is the process of producing light by heating. This works because thermal radiation is emitted because of the object’s temperature. At room temperature, most objects don’t emit radiation in the visible spectrum, but at high temperature they can.