Question

An electric lamp glows due to

A) Chemical effect

B) Magnetic effect

C) Heating effect

D) None of the above

Answer 1

Hint: When a current crosses through a conductor, heat energy is created in the conductor. The heating effects of current depend on three elements: The conductor's resistance; A greater resistance gives more heat. The time for which the current flows. The more delayed the time, the higher the heat generated. The greater the current, the heat generation is also significant. Hence the heating effect presented by an electric current, I through a conductor of resistance, R for a time, t is an equation explained by Joule’s equation of heating.

Complete step-by-step solution:

The electric lamp glows because of the heating effect of the electric current.

There is a relation between heat generated and the amount of electric current; it is given by the Joule’s effect of heat. Joule’s law is a mathematical representation of the rate at which circuit's resistance converts electrical energy into light energy.

$ H = I^{2}RT $ 

$H$ is the amount of heat released.

$I$ is the current magnitude.

$R$ is the resistance of filament.

$T$ is the time taken.

The amount of released heat is proportional to the square of the magnitude of the current, so, when current passes, a large amount of heat will be released.

As the current moves through the lamp, it burns the lamp filament, which provides off the light. A lamp filament has much resistance or opposition to electricity. The filament that glows up and becomes red-hot; thus, it starts to glow, utilizing electrical energy converting into light energy. Due to the Joule effect, as the electrical current passes through them, the resistances heat up.

Therefore, Option (C) is correct.

Note: 

An electric lamp carries a thick metallic wire formed up of tungsten elements. The metal is put in an inert atmosphere with a vacuum or neutral gas. When current flows by the tungsten wire, it grows heated and emits radiation. Most of the power carried in the circuit from the electrical source is wasted in the form of heat, and the rest is released in the form of light energy.