What is an Incandescent Lamp? – Construction, Working and Applications

An electric light bulb or lamp that produces light by heating a filament wire to a high temperature until it glows is known as incandescent bulb. The incandescent bulb was invented by an American inventor, named Thomas Alva Edison.

The incandescent bulb is an electric lamp that works on the principle of incandescence that means it emits light by the heating of a filament. The incandescent lamps come in different sizes with different voltages and wattages.

Construction of Incandescent Lamp

The construction and the parts of an incandescent lamp is shown in the figure below.

The most important part of the incandescent lamp is its filament. The filament is made of specially treated tungsten to provide it the necessary ductility and mechanical strength. The filament material has a low temperature coefficient of resistance which is positive.

For the tungsten filament, the cold resistance is about 1/5th of the hot resistance of the filament and its operating temperature is about 2700 °C to 3000 °C. At this high temperature, the filament material does not sublimate. Also, the melting point of tungsten is 3400 °C, thus it can work at such a high temperature and its lumens per watt efficiency depends upon the working temperature.

In the incandescent lamp, the tungsten filament. supported by the thin support wires, is enclosed in a glass cover which is either evacuated or filled with an inert gas. The inert gas used to fill the lamp is argon and nitrogen, which prevents the oxidation of the filament.

In practice, the incandescent lamps below 40 W are not filled with the gas. It is because, a lot of heat is wasted in the small sized lamps due to convectional flow of the gas which will transfer the heat from the filament to the glass walls of the lamp, and this will reduce the lumens emitted by the filament.

The type and color used for the glass cover produce a vital effect on the quality of light produced by the incandescent lamp, for example, the milky glass cover gives a light output which is almost natural in effect like day light.

Working of Incandescent Lamp

The incandescent lamps work on the principle of incandescence that means light is emitted by the heating of a filament.

In case of incandescent lamp, the electric current is passed through a thin metal (commonly tungsten) filament, which causes the filament to heat. Once the filament is heated, it flows to emit light.

Advantages of Incandescent Lamps

The main advantages of the incandescent lamps are as −

  • They can be operated directly on the standard distribution voltage.

  • Incandescent lamps have unity operating power factor.

  • Their operation is not affected by the surrounding air temperature.

  • They have good radiation characteristics in the luminous range.

  • The incandescent lamps are available in various shapes and shades.

Disadvantages of Incandescent Lamps

The disadvantages of the incandescent lamps are given below.

  • They waste large amount of input energy in the form of heat, thus the incandescent lamps are not energy efficient.

  • Incandescent lamps have short life span.

  • Incandescent lamps are the warm light sources.

Applications of Incandescent Lamps

The applications of the incandescent lamps are given as follows −

  • Incandescent lamps are widely used in household and commercial lightings.

  • Other applications of the incandescent lamps include table lamps, hallway lighting, accent lighting, closets, etc.