Question

Explain the working of LED and what are its advantages over conventional incandescent low power lamps

Answer 1

Light emitting diode (LED) :

• It is a photoelectronic device which converts electrical energy into light energy.

• It is a heavily doped p-n junction diode which under forward bias emits spontaneous radiation.

• The diode is covered with a transparent cover so that the emitted light may be come out .

Working :

• When p-n junction diode is forward biased, the movement of majority charge carriers takes place across the junction.

• The electrons move from n-side to p-side through the junction and holes move from p-side to n-side.

• As a result of it, concentration of majority carriers increases rapdily at the junction.

• When there is no bias across the junction, there are excess minority carriers on either side of the junction, which recombine with majority carriers near the junction.

• On recombination of electrons and holes, the energy is given out in the form of heat and light.

Advantages of LED's over incandescent lamp :

• LED is a cheap and easy to handle.

• LED has less power and operational voltage.

• LED has fast action and requires no warm up time.

• LED can be used in burglar alarm system.

Answer 2

Explain the working of LED and what are its advantages over conventional incandescent low power lamps