An incandescent light
bulb, incandescent lamp or incandescent light globe is an electric light with a
wire filament heated to such a high temperature that it glows with visible
light (incandescence). The filament, heated by passing an electric current
through it, is protected from oxidation with a glass or fused quartz bulb that
is filled with inert gas or evacuated. In a halogen lamp, filament evaporation
is slowed by a chemical process that redeposits metal vapor onto the filament,
extending its life. The light bulb is supplied with electric 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 much less efficient than most other types of electric lighting;
incandescent bulbs convert less than 5% of the energy they use into visible
light, with standard light bulbs averaging about 2.2%. The remaining energy is
converted into heat. The luminous efficacy of a typical incandescent bulb is 16
lumens per watt, compared with 60 lm/W for a compact fluorescent bulb or 150 lm/W
for some white LED lamps. Some applications of the incandescent bulb (such as
heat lamps) 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,
lava lamps, and the Easy-Bake Oven toy. Incandescent bulbs typically have short
lifetimes compared with other types of lighting; around 1,000 hours for home
light bulbs versus typically 10,000 hours for compact fluorescents and 30,000
hours for lighting LEDs.
Incandescent bulbs
have been replaced in many applications by other types of electric light, such
as fluorescent lamps, compact fluorescent lamps (CFL), cold cathode fluorescent
lamps (CCFL), high-intensity discharge lamps, and light-emitting diode lamps
(LED). Some jurisdictions, such as the European Union, China, Canada and United
States, are in the process of phasing out the use of incandescent light bulbs
while others, including Colombia, Mexico, Cuba, Argentina and Brazil, have
prohibited them already.
Thomas Edison
On October 21, 1879,
Thomas Edison devised a workable electric light at his laboratory in Menlo
Park, N.J. A New York Times reporter visited Edison there and wrote an article
about it that appeared in the paper on Dec. 28, 1879. “The lamp which Mr.
Edison regards as a crowning triumph is a model of simplicity and economy,” he
said.
Edison was not the
first man to create incandescent light. The English scientist Humphrey Davy
built a powerful electric lamp in the early 1800s; The Englishman Joseph Swan
received a patent on a bulb in 1878 that Edison studied while building his own.
Edison’s feat was
creating a lamp that lasted longer and required less power than previous
designs that were impractical for everyday use. He also, through his Edison
Electrical Light Company (today, General Electric), built a system of power
stations to deliver the electricity needed to run his bulbs; he discussed his
plans for this in the same New York Times article.
Edison’s light bulb
was one great achievement in his brilliant career. Known as the “Wizard of
Menlo Park,” Edison received more than 1,000 patents for his work and created
or improved upon items like the phonograph, the motion picture camera and a
battery for vehicles.
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