Around 1880, many research experiments were being conducted for the development of a constant electric light bulb. Thomas Edison had acquired a US patent for “an electric lamp using carbonized filament” which could last for up to 1200 hours. Though they had developed an electric light bulb (incandescent lamp), they could not sell the bulbs commercially because no electrical network (or power system) was present at the time. Edison’s company developed DC power plants to supply the electricity publically for electric lighting using incandescent lamps. Those Edison’s DC power plants were replaced by AC power plants as a result of the war of currents. Incandescent lamps were rapidly adopted to replace the gas lighting. They underwent many developments for increasing their life and luminosity, carbonized filaments were replaced by tungsten filaments. Edison’s Incandescent lamps stayed the only option of electric lighting for a long time. They are used to some extent even today.
Incandescent lamps are available in a wide range of sizes, shapes and voltage ratings (as low as 1.5 up to as high as 300 volts). They are extremely cheaper because of their simple construction and absence of any additional electronic circuitry. That is why they are still being used despite having better efficient options such as CFL and LED lamps. Incandescent lamps are the least efficient type of electric lighting.
How does an Incandescent Lamp work?
The construction of an incandescent lamp is very simple, which can be clearly understood from the picture below. There are two metal contacts at the base, which are used to connect the bulb to an electric supply. The metal contacts are attached to a ‘thin metal filament’ via a thin wire. The metal filament is usually made up of tungsten. In a typical 60 watt bulb, the tungsten filament is about 2 meters long and only one hundredth of an inch thick. The filament and wire are housed in a glass bulb, which is filled with an inert gas (like argon).
- When an incandescent lamp is connected to an electric supply, an electric current flows through the tungsten filament.
- Due to very thin cross section and very long length, the resistance of filament is very high which causes the production large amount of heat due to the electric current.
- The filament goes so hot that it would catch fire when exposed to oxygen and, therefore, it is housed in a glass bulb filled up with an inert gas such as argon.
- The filament at extreme temperature glows and emits visible light.
This is how an incandescent lamp works!