What is the difference between a halogen and an incandescent light bulb?
Halogen light bulbs utilize a fused quartz envelope (“capsule”) allowing for higher temperatures. Inside the quartz envelope is a vapor, originally iodine, now usually bromine. The tungsten filament evaporates as usual but the higher temperatures are sufficient to cause the tungsten to mix with the vapor instead of depositing on the envelope. Some of the evaporated tungsten is re-deposited on the filament. The combination of this “regenerative cycle” and higher filament temperature results in a bulb that has a longer life and slightly higher efficiency than standard incandescent bulbs. The higher temperature filament also produces the “white” light often associated with halogen bulbs. Where does the term halogen come from? Halogen is the name given to a family of electronegative elements, including bromine, chlorine, fluorine and iodine. Halogen bulbs are referred to variously as “tungsten halogen,””quartz halogen” or simply “halogen.” The term “J” bulb (some manufacturers use the lett
