Explain how the heating effect of electric current is utilized in… - Vidyadip

Question

Explain how the heating effect of electric current is utilized in an electric butb (called incandescent lamp) to produce light.

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Answer

When an electric current passes through a very thin, high-resistance tungsten filament of an electric bulb, the filament becomes white-hot and emits light.
$\rightarrow$ Here, tungsten metal is used for making the filament of an electric bulb because it has a very high melting point (of $3380^{\circ} C$ ). Due to its very high melting point, the tungsten filament can be kept white-hot without melting away.

$\rightarrow$ The other properties of tungsten which make it suitable for making filament of an electric bulb are its high flexibility and law rate of evaporation at high temperature.
$\rightarrow$ If air is present in an electric bulb, then the extremely hot tungsten filament would burn up quickly in the presence of oxygen in air.
$\rightarrow$ So, the electric bulb is filled with a chemically nonreactive (inactive) gas like argon or nitrogen (or a mixture of both). The gases like argan and nitrogen do not react with the hot tungsten filament and hence prolong the life of the filament of the electric bulb.
$\rightarrow$ In electric bulb, most of the electric energy (power) consumed by the filament appears as heat (due to which the bulb becomes hot), only a small amount of electric energy (power) is converted into light.
So, filament type electric bulbs are not power-efficient. On the other hand, tube lights are much more power efficient because they have no filaments.

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