Halogen Lamps, How Halogen Lamps work


Incandescent lamp is very simple in construction and principle. Electrons when flow through a resistance generates heat. More the resistance more the heat. In this lamp a high resistance tungsten filament is used. When a voltage is applied the tungsten filament gets red hot and glows.


The problem is when it glows it causes a slow evaporation of the tungsten filament. The evaporated tungsten deposits on the inner side of the glass bulb and blackens the bulb. This dims the glow of the bulb, and also there is a loss of material from the filament. Eventually the filament weakens and breaks.


To solve this problem this bulb is modified a little bit.
Halogen materials are chemicals elements that are very active to react with metal and form salt. Iodine and Bromine are halogen.

In a halogen lamp a little bit of Bromine or Iodine is introduced inside the bulb. When the tungsten evaporates it reacts with the Bromine/Iodine and form salt. And at higher temperature the salt breaks down to Tungsten and Bromine/Iodine again, the tungsten deposits on the high temperature region i.e., filament. Thus the vaporization redeposition takes place in cycle. This is called Halogen Cycle. As the temperature of halogen lamp is very high, the glass is also made from fused quartz or Aluminosilicate to withstand it.


Thus Halogen Lamps are modified incandescent lamps with longer life. And can be operated with high power (high temperature. )

Halogen lamps are used in lighting open areas, theatres, stadium, airports and specially for Photography. Also used for car and bike headlamps . Sometimes it is also used for heating purpose.

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