Halogen Light Bulbs Key Terms

Turning on the light to halogen light bulb terminology

By Jennifer Ehlenfeldt, Freelance Writer

Halogen light bulbs have been around since the late 1950s and remain popular choices for automobile headlights and other applications that require really bright lights. If you're in the market for halogen light bulbs, do a little due diligence first and make sure you understand the terminology associated with halogen light bulbs before you begin shopping for them.

This guide addresses six terms associated with halogen light bulbs: halogen, tungsten filament, halogen cycle, filament necking, A-line halogen bulbs and Parabolic Aluminized Reflectors.

Halogen

Halogens are five nonmetallic elements that are chemically related: fluorine, astatine, chlorine, iodine and bromine. Halogen bulbs are filled with a halogen gas that often includes traces of iodine. In halogen bulbs, the gas combines with evaporated tungsten atoms during the halogen cycle.
Try: Read more detailed information about halogen at Encyclopedia.com.

Tungsten filament

A tungsten filament is the metal part inside a halogen bulb. Enclosed inside a quartz envelope, the tungsten filament must reach a high enough temperature to produce the desired amount of light. Tungsten is a corrosion-resistant, hard, brittle metallic element that boasts the lowest vapor pressure and highest melting point of all metals. Its melting point is 3,410 degrees Celsius.
Try: Learn more about tungsten filaments and how they work at HowStuffWorks.

Halogen cycle

The halogen cycle is the process within halogen bulbs where tungsten filament particles first evaporate due to of heat. The evaporated tungsten material then collides with, and bonds chemically to, the halogen. Finally, the tungsten particles get redeposited on the filament, helping to extend the life of bulb.
Try: Get more details about the halogen cycle and view a flash animation demonstration of the halogen cycle at the GoodMart website.

Filament notching

In halogen bulbs, filament notching, also called filament necking, is one way halogen bulbs can fail. When the halogen bulb is turned on, the ends or necks of the filament heat faster than the rest of the filament and create thin spots that can break or melt if overheated. Devices called soft starts will keep the necks from overheating.
Try: Visit Robinson Lighting & Bath Centre and scroll down to the sections on "Care and Safety" and "Use of Halogen Bulbs with Dimmers" to learn more about how dimmers impact filament necking and halogen lamp failure.

A-line halogen bulbs

A-line halogen bulbs are lamps that come in the classic pear shape of traditional light bulbs but boast the long life of halogen bulbs. They're also called A-shaped or A-type halogen bulbs.
Try: View the features of A-line halogen bulbs at 1000Bulbs.com.

Parabolic Aluminized Reflectors (PAR)

A Parabolic Aluminized Reflector is a lamp commonly used in transportation, commercial and residential applications that include aircraft landing lights and train headlamps. PARs can be incandescent or halogen.
Try: Scroll down about one-third of the page at Best Home Systems to get more information on Parabolic Aluminized Reflectors.