Electric light sources:(Incandescent or filament lamp, discharge lamp, CF & Led lamps)

Electric light sources
One of the effects of electricity is light effect. In our daily life, we use different types of electric lamps. Let’s see what are they? Incandescent lamp or filament lamp, fluorescent lamp, discharge lamp, CF lamp, LED lamp etc.
What is an incandescent lamp?
The main part of an incandescent lamp is the tungsten filament. The thin tungsten filament is made into coils and enclosed in a glass bulb. The two terminals of the filament are connected to two thick metal sheets. These two sheets are connected to two outside metal points.
The first person who introduced the filament lamp was Thomas Alva Edison. He had done so many experiments to find a suitable material as filament in electric bulb.
How does an incandescent light bulb work?
When electricity is passes through the filament of the incandescent lamp, then it becomes white hot and emits white light.
The air inside the lamp is replaced by an inert gas to increase its life.
Let’s see the merits of using noble gas inside an incandescent lamp.
1. The evaporation of the filament is less.
2. The efficiency and life of the bulb is more.
3. Avoids darkening of the bulb.
4. Controls the temperature of the bulb within a limit.
Discharge Lamps
The important part of a discharge tube is a glass tube containing suitable air at low pressure. The bulb consists of two electrodes at each corner. A high voltage is applied to the electrodes. The gas inside the tube gets ionized. As a result of the collision of the ions and electrons with unionized particles, light is produced.
The colour of the light from the lamp depends upon the nature of gas filled in the tube.
Sodium vapour lamp produces yellow light, whereas Mercury vapour lamp gives white light, Neon lamp emits orange red light, Hydrogen produces blue light, Chlorine produces green and Nitrogen produces red light.
CFL
Nowadays CF lamps are used for reducing the usage of electricity. As compared with fluorescent lamps, the length of CF lamps are less.
CFL mainly consists of a unit of electronic circuit and a fluorescent tube containing mercury vapour. With the help of electronic circuit, high frequency electricity is supplied between the electrodes of the tube. As a result electrons are emitted from the electrodes. Collision between electrons and the mercury vapour produces UV rays inside the tube. The fluorescent coating inside the tube absorb these UV rays and convert it into visible rays.
Merits of CFL
1. Low power is sufficient
2. Convert major part of energy supplied to light.
3. The life span is 5 times more than filament lamp.
4. Provide intense light.
LED (Light Emitting Diode)
LED is an electronic device which converts electrical energy into light energy using very little power. Today LEDs in different colours is available in the market.
By the way manufacturing, LED lamps give different colours. The LED provides white light are called white LEDs. White LEDs are used as street light, head lamps of vehicles and other household applications.