ARC LAMPS                              

ARC LAMPS

THESE ARE THE LAMPS ARE USED IN SEARCHLIGHTS, PROJECTION LAMPS, AND OTHER SPECIAL-PURPOSE LAMPS LIKE THOSE IN FLASH CAMERAS. IN AN ARC LAMP ELECTRIC CURRENT IS MADE TO FLOW THROUGH TWO ELECTRODES IN CONTACT WITH EACH OTHER WHICH ARE DRAWN APART. THE RESULT IS AN BEING STRUCK. THE ARC MAINTAINS THE CURRENT AND IS A VERY EFFICIENT SOURCE OF LIGHT.

THE VARIOUS FORMS OF ARC LAMPS ARE:-

1. CARBON ARC LAMP

2. FLAME ARC LAMP

3. MAGNETIC ARC LAMP

THE CARBON RODS USED WITH A.C SUPPLY ARE OF THE SAME SIZE AS THAT USED WITH D.C SUPPLY.

THE CRATERS IN THE ARC ARE AT THE POSITIVE AND NEGATIVE RODS ARE OF THE SAME SIZE WITH A.C SUPPLY WHILE THE DC SUPPLY, THE POSITIVE CRATER IS BIGGER AND GIVES 85% LIGHT AT A TEMPERATURE OF 3500 DEGREES CELCIUS, WHILE THE NEGATIVE CRATER IS OF SMALLER SIZE. THE EFFICIENCY OF THE LAMP IS 9 LUMENS/WATT.

THE POSITIVE ELECTRODE GETS CONSUMED EARLIER THAN THE NEGATIVE ELECTRODE IF THE SIZE OF THE FORMER IS THE SAME AS THE LATTER. HENCE THE POSITIVE ELECTRODE IS OF TWICE THE DIAMETER THAN OF THE NEGATIVE.

A RESISTANCE IS USED TO STABILISE THE ARC.

THE VOLTAGE DROP ACROSS THE ARC IS ABOUT 60V AND THE SUPPLY VOLTAGE IS UP TO 100V.