Incandescent Light Bulb
The incandescent light bulb, incandescent
lamp or incandescent light globe produces light
by heating a filament wire to a high temperature
until it glows. The hot filament is protected from
oxidation in the air with a glass enclosure that
is filled with inert gas or evacuated. In a halogen
lamp, filament evaporation is prevented by a chemical
process that redeposits metal vapor onto the filament,
extending its life. The light bulb is supplied with
electrical current by feed-through terminals or
wires embedded in the glass. Most bulbs are used
in a socket which provides mechanical support and
electrical connections.
Incandescent bulbs are manufactured in a wide range
of sizes, light output, and voltage ratings, from
1.5 volts to about 300 volts. They require no external
regulating equipment, have low manufacturing costs,
and work equally well on either alternating current
or direct current. As a result, the incandescent
lamp is widely used in household and commercial
lighting, for portable lighting such as table lamps,
car headlamps, and flashlights, and for decorative
and advertising lighting.
Incandescent bulbs are highly wasteful, with most
varieties converting less than 10% of the energy
they use into visible light, with the remaining
energy used being converted into heat. Some applications
of the incandescent bulb deliberately use the heat
generated by the filament. Such applications include
incubators, brooding boxes for poultry, heat lights
for reptile tanks, infrared heating for industrial
heating and drying processes, and the Easy-Bake
Oven toy. But waste heat can also significantly
increase the energy required by a building's air
conditioning system.
Incandescent light bulbs are gradually being replaced
in many applications by other types of electric
lights, such as fluorescent lamps, compact fluorescent
lamps (CFL), cold cathode fluorescent lamps (CCFL),
high-intensity discharge lamps, and light-emitting
diodes (LEDs). These newer technologies improve
the ratio of visible light to heat generation. Some
jurisdictions, such as the European Union, are in
the process of phasing out the use of incandescent
light bulbs in favor of more energy-efficient lighting.
(Source: Wikipedia.org)
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