A light bulb that produces a soft warm light by electrically heating a tungsten filament so that it glows. Because so much of the energy is lost as heat, these are highly inefficient sources of light. The light bulb produces light by passing electricity through mercury vapor, causing the fluorescent coating to glow, or fluoresce. Excluded are compact fluorescent light bulbs, which are listed in a separate category. They combine the efficiency of fluorescent lighting with the convenience of standard incandescent bulbs.
Light is produced the same way as other fluorescent lamps.
Compact fluorescent bulbs have either electronic or magnetic ballasts. A lamp bulb that produces light by passing electricity through gas, which causes the gas to glow. HID lamps have an extremely long life and emit many more lumens per fixture than do fluorescent lights. A type of incandescent light bulb that lasts much longer and is more efficient than a standard incandescent light bulb. The light bulb uses a halogen gas, usually iodine or bromine, that causes the evaporating tungsten to be redeposited on the filament, thus prolonging its life.