The incandescent light bulb, incandescent lamp or incandescent light globe is a source of electric light that works by incandescence, (a general term for heat-driven light emissions which includes the simple case of black body radiation). An electric current passes through a thin filament, heating it until it produces light. The enclosing glass bulb prevents the oxygen in air from reaching the hot filament, which otherwise would be destroyed rapidly by oxidation. Incandescent bulbs are also sometimes called electric lamps, a term also applied to the original arc lamps.

Some applications of the incandescent bulb make use of the heat generated, such as incubators (for hatching eggs), brooding boxes for young poultry, heat lights for reptile tanks, infrared heating for industrial heating and drying processes, and the Easy-Bake Oven toy. In cold weather the heat shed by incandescent lamps contributes to building heating, but in hot climates lamp losses increase the energy used by air conditioning systems.

A fluorescent lamp or fluorescent tube is a gas-discharge lamp that uses electricity to excite mercury vapor. The excited mercury atoms produce short-wave ultraviolet light that then causes a phosphor to fluoresce, producing visible light.

Unlike incandescent lamps, fluorescent lamps always require a ballast to regulate the flow of power through the lamp. However, a fluorescent lamp converts electrical power into useful light more efficiently than an incandescent lamp; lower energy costs offsets the higher initial cost of the lamp. While larger fluorescent lamps have been mostly used in large commercial or institutional buildings, the compact fluorescent lamp is now being used as an energy-saving alternative to incandescent lamps in homes. Compared with incandescent lamps, fluorescent lamps use less power for the same amount of light, generally last longer, but are bulkier, more complex, and more expensive than a comparable incandescent lamp.

Government action has led to reduced use of, and the decision of some governments to begin, the banning of incandescent light bulbs; large increases in the use of more energy efficient lighting alternatives, such as compact fluorescent lamps and LED lamps, have in part been attributed to governmental initiatives. Aus­tralia is phasing out inefficient incandescent light bulbs by introducing mandatory energy performance standards. The European Union, Ireland, and Canada have announced plans to ban incandescent bulbs. The United States has also passed legislation increasing the efficiency standard required for lightbulbs, which will effectively phase out incandes­cents. In total, more than 40 countries have announced plans relating to the banning of incandescent lightbulbs.

The cost of compact fluorescent lamps (CFLs) is considerably higher than incandescent light bulbs, and there are some applications where the extra cost of a CFL will never be repaid, typically where bulbs are used relatively infrequently such as in little-used closets and attics.

There has been some consumer concern that CFLs may not fit existing light sockets or lampshades. However, manufacturers state that CFLs are substantially shorter and smaller than they were just a few years ago. While some CFLs had difficulty fitting certain lampshades in the past, they will usually fit in table lamps today.

There has also been concern that CFLs cause interference in TV pictures and AM radio. This used to be true: some CFLs created radio frequency interference, but this is rare today. In the U.S., manufacturers state that the problem can be avoided by choosing CFLs with the government's Energy Star rating, indicating that they meet a standard set by the Federal Communications Commission (FCC). The FCC also requires CFL manufacturers to supply information (on or inside the package) that informs consumers what to do in the event of any interference (e.g., move the CFL and AM radio away from each other).

Using CFLs in a home will not affect power quality appreciably, but their use in large-scale installations can have an impact.

Modern CFLs contain about 4 milli­grams of mercury, a dangerous neurotoxin. This is less than 1 percent as much mercury as found in old thermometers, but broken bulbs should be treated with care and discarded bulbs should be recycled. The EPA recommends that the room be vacated for at least 15 minutes with a window open, then the broken material carefully disposed of should a bulb break.

CFLs also cannot be used in some older dimmer light fixtures and with some electric timers, meaning many people will be forced to replace fixtures, switches and timers with those which are compatible, as well as purchasing special CFL bulbs that can be used with this hardware.

For More Information:
Incandescent Light Bulb: K-12 Experiments & Background Information
Fluorescent Lamp

Source: Wikipedia (All text is available under the terms of the GNU Free Documentation License)