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Incandescent light bulb

An incande scent light bulb

From Wikipedia, the free encyclopedia

"Light bulb" redirects here. For other types including compact fluorescent lamps , see Lamp (electrical component).

The incandescent light bulb , incandescent lamp or incandescent light globe makes light

by heating a metal filament wire to a high temperature until it glows. The hot filament is protected

from air by a glass bulb that is filled with inert gas or evacuated. In a halogen lamp, a chemical

process that returns metal to the filament prevents its evap oration. The light bulb is supplied with

electrical current by feed- through terminals or wires embedd ed in the glass . Most bulbs are used in

a so cket (a housing giv ing mechanical supp ort to the bulb, keep ing its terminals in co ntact with the

supply current terminals).

Incandescent bulbs are produced in a wide range of sizes, light output, and voltage ratings, from1.5 volts to about 300 volts. They require no external regulating equipment and have a low

manufacturing cost 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, carheadlamps, and flashlights, and fordecorative and advertising lighting.

Some applications of the incandescent bulb use the heat generated by the filament, such as

incubators, brooding boxes forpoultry, heat lights for reptiletanks,[1][2]infrared heating for industrial

heating and drying processes, and the Easy-Bake Oven toy. In cold weather, the heat produced by

incandescent lamps is a benefit as it contributes to building heating, but in hot climates this waste

heat increases the energy required by air conditioning systems.

Incandescent light bulbs are gradually being replaced in many applications by other typ es of

electric lights, such as fluorescent lamps, compact fluorescent lamps , cold cathode fluorescent

lamps (CCFL), high-intensity discharge lamps, and light-emitting diodes (LEDs). These newer

technologie s improve the ratio of visib le light to heat generation. Some jurisdictions, such as the European Union, are in the process of

phasing out the use o f incandescent light bulbs in favor of more energy- efficient lighting. In the United States, federal la w has scheduled

the most common incandescent light bulbs to be phased o ut by 2014, to be replaced with more energy- efficient light bulbs.[3] In Brazil,

they have already been phased out.[when?][citation needed]. Traditional incandescent light bulbs were phased out in Australia in November

2009.[4 ]

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://en.wikipedia.org/wiki/Incandescencehttp://en.wikipedia.org/wiki/File:Gluehlampe_01_KMJ.pnghttp://en.wikipedia.org/wiki/File:Gluehlampe_01_KMJ.pnghttp://en.wikipedia.org/wiki/Lamp_(electrical_component)http://en.wikipedia.org/wiki/Compact_fluorescent_lamp


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Contents[hide]

1 History of the light bulb

1.1 Early pre-comm ercial research

1.2 Commercialization

1.3 Cartels

2 Efficiency and environm ental impact

2.1 Cost of lighting

2.2 Measures to ban its us e

2.3 Efforts to im prove efficiency

3 Construction

4 Manufacturing

5 Filament

5.1 Reducing filament evapo ration

5.2 Bulb blackening

5.3 Halogen lamps

5.4 Incandescent arc lamps

6 Electrical characteristics6.1 Power

7 Physical characteristics

7.1 Bulb shapes, siz es, and terms

7.2 Lamp bases

8 Voltage, light output, and lifetime

9 Health issues

10 Radio interference

11 See als o

12 References

13 External links

History of the light bulb

[5 ]

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Carbon filament lamp (E27 socket,

220 volts, approx. 30 watts, left side:running with 100 volts)

In North America, pa rallel developments were taking place . On July 24, 1874, a Canadianpatent was filed by a Toronto medical

electrician named Henry Woodward and a colleague Mathew Evans. They built their lamps with different size s and shapes o f carbon

rods held between electrodes in glass cylinders filled with nitrogen. Woodward and Evans attempted to commercialize their lamp, but

were unsuccessful. They ended up selling their patent (U.S. Patent 0,181,613 ) to Thomas Edison in 1879.[22][23]

Commercialization

Joseph Swan (18281914) was a British physicist and chemist. In 1850, he began working with

carbonized paper filaments in an evacuated glass bulb. By 1860, he was able to demonstrate aworking device but the lack of a good vacuum and an adequate supply of electricity resulted in

a short lifetime for the bulb and an inefficient source of light. By the mid- 1870s better pumps

became available, and Swan returned to his experiments.

With the help o f Charles Stearn, an expert on vacuum pumps, in 1878, Swan de veloped a

method of process ing that avoided the ea rly bulb blackening. This received British Patent No 8

in 1880.[24] On 18 December 1878, a lamp using a slender carbon rod was shown at a meeting

of the Newcastle Chemical Society, and Swan gave a working demonstration at their meeting on

17 January 1879. It was a lso shown to 700 who a ttended a mee ting of the Literary and

Philosophical Society ofNewcastle upon Tyne on 3 February 1879. These lamps used a carbon

rod from an arc lamp rather than a slender filament. Thus they had low resistance and requiredvery large conductors to supply the necessary current, so they were not commercially practical,

although they did furnish a demonstration of the possibilities of incandescent lighting with

relatively high vacuum, a carbo n conductor, and p latinum lead- in wires. Besides requiring too

much current for a central station electric system to be p ractical, they had a very short lifetime.[25] Swan turned his attention to producing a

better carbon filament and the means of attaching its ends. He de vised a method of treating co tton to produce 'parchmentised thread ' and

obtained British Patent 4933 in 1880.[24] From this yea r he beg an installing light bulbs in homes and landmarks in England. His house

was the first in the world to be lit by a lightbulb and so the first house in the world to be lit by Hydro Electric power. In the early 1880s he

had started his company.[26] In 1881, the Savoy Theatre in the City of Westminster, London was lit by Swan incandescent lightbulbs,

which was the first theatre, and the first public building in the world, to be lit entirely by electricity.[27]

Thomas Edison began serious research into de velop ing a prac tical incandescent lamp in 1878. Edison filed his first patent application for"Improvement In Electric Lights" o n October 14, 1878.[28] After many experiments with platinum and other metal filaments, Edison returned

to a carbon filament. The first successful test was on October 22, 1879, [29] and lasted 13.5 hours. Edison continued to improve this

design and by November 4, 1879, filed for a U.S. patent for an elec tric lamp using "a carbon filament or strip co iled and connected ... to

platina contact wires."[30] Although the patent described several ways o f creating the carbo n filament including using "cotton and linen

thread, wood splints, papers coiled in various ways,"[30] it was not until several months after the patent was granted that Edison and his

team discovered that a carbonized bamboo filament could last over 1200 hours.

Hiram S. Maxim started a lightbulb company in 1878 to exploit his patents and those ofWilliam Sawyer. His United States Electric Lighting

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http://pdfmyurl.com/?otsrc=watermark&otclc=0.01http://pdfmyurl.com/?otsrc=watermark&otclc=0.01http://en.wikipedia.org/wiki/William_E._Sawyerhttp://en.wikipedia.org/wiki/Hiram_S._Maximhttp://en.wikipedia.org/wiki/Incandescent_light_bulb#cite_note-Patent898-29http://en.wikipedia.org/wiki/Incandescent_light_bulb#cite_note-Patent898-29http://en.wikipedia.org/wiki/Incandescent_light_bulb#cite_note-28http://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Incandescent_light_bulb#cite_note-27http://en.wikipedia.org/wiki/Thomas_Edisonhttp://en.wikipedia.org/wiki/Incandescent_light_bulb#cite_note-Times-26http://en.wikipedia.org/wiki/Electricityhttp://en.wikipedia.org/wiki/City_of_Westminsterhttp://en.wikipedia.org/wiki/Savoy_Theatrehttp://en.wikipedia.org/wiki/Incandescent_light_bulb#cite_note-25http://en.wikipedia.org/wiki/Incandescent_light_bulb#cite_note-Incandescent_Electric_Lamp_Pp_21-25-23http://en.wikipedia.org/wiki/Incandescent_light_bulb#cite_note-24http://en.wikipedia.org/wiki/Newcastle_upon_Tynehttp://en.wikipedia.org/wiki/Literary_and_Philosophical_Society_of_Newcastle_upon_Tynehttp://en.wikipedia.org/wiki/Incandescent_light_bulb#cite_note-Incandescent_Electric_Lamp_Pp_21-25-23http://en.wikipedia.org/wiki/Joseph_Swanhttp://en.wikipedia.org/wiki/Watthttp://en.wikipedia.org/wiki/Volthttp://en.wikipedia.org/wiki/File:Carbonfilament.jpghttp://en.wikipedia.org/wiki/File:Carbonfilament.jpghttp://en.wikipedia.org/wiki/Incandescent_light_bulb#cite_note-22http://en.wikipedia.org/wiki/Incandescent_light_bulb#cite_note-21http://www.google.com/patents?vid=181613http://en.wikipedia.org/wiki/Nitrogenhttp://en.wikipedia.org/wiki/Electrodeshttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Mathew_Evanshttp://en.wikipedia.org/wiki/Henry_Woodward_(inventor)http://en.wikipedia.org/wiki/Torontohttp://en.wikipedia.org/wiki/Patenthttp://en.wikipedia.org/wiki/Canada


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U.S. Patent0,223,898 by ThomasEdison for an improved

electric lamp, January27, 1880

Company was the second company, after Edison, to sell practical incandescent electric lamps. They mad e their first commercial

installation of incandescent lamps a t the Mercantile Safe Depo sit Company in New York City in the fall of 1880, about six months after the

Edison incandescent lamps had been installed on the steamer Columbia. In October 1880, Maxim patented a method of coating carbon

filaments with hydrocarbons to extend their life. Lewis Latimer, his employee at the time, developed an improved method of heat-treating

them which reduced breakage and allowed them to be molded into novel shapes, such as the characteristic "M" shape of Maxim

filaments. On January 17, 188 2, Latimer receive d a patent for the "Process of Manufacturing Carbons," an improved method for the

production of light bulb filaments, which was purchased by the United States Electric Light Company. Latimer patented other improvements

such as a better way of attaching filaments to their wire supports.[31]

In Britain, the Edison and Swan co mpanies merged into the Edison and Swan United Electric Company (later known as Ediswan, that was

ultimately incorporated into Thorn Lighting Ltd). Edison was initially against this combination, but after Swan sued him and won, Edison

was eve ntually forced to co operate, and the merger was made. Eventually, Edison acquired all of Swan's interest in the co mpany. Swan

sold his United States patent rights to the Brush Electric Company in June 1882.

In 1882, the first recorded set of miniature incandescent lamps for lighting a Christmas tree was installed.

These did not become common in homes for many years.

The United States Patent Office gave a ruling October 8, 1883, that Edison's patents were based on the prior

art ofWilliam Sawyerand were invalid. Litigation continued for a number of years. Eventually on October 6,

1889, a judge ruled that Edison's elec tric light improvement claim for "a filament of carbon of high resistance"

was valid.In the 1890s, the Austrian inventor Carl Auer von Welsbach worked on metal-filament mantles, first with

platinum wire, and then osmium, and produced an operating version in 1898. In 1898, he patented the osmium

lamp a nd started marketing it in 1902, the first commercial metal filament incandescent lamp.

In 1897, German physicist and chemist Walther Nernst developed the Nernst lamp, a form of incandescent

lamp that used a ceramic globarand did not require enclosure in a vacuum or inert gas. Twice as efficient as

carbon filament lamps, Nernst lamps were b riefly po pular until overtaken by lamps using metal filaments.

In 1903 , Willis Whitnew invented a metal- coated carbon filament that would not blacken the inside of a light

bulb.

On December 13, 1904, HungarianSndor Just and CroatianFranjo Hanaman were granted a Hungarianpatent (No. 34541) for a tungsten filament lamp, that lasted longer and gave a brighter light than the ca rbon

filament. Tungsten filament lamps were first marketed by the Hungarian company Tungsram in 1905, so this

type is o ften called Tungsram-b ulbs in many European countries.[32] Experiments also showed that the luminosity of bulbs that were filled

up with an inert gas was higher.[33]

In 1906, the General Electric Company patented a method of making filaments from sintered tungsten and in 1911, used ductile tungsten

wire for incandescent light bulbs. The tungsten filament outlasted a ll other types.

In 1913, Irving Langmuirfound that filling a lamp with inert gas instead of a vacuum resulted in twice the luminous efficacy and reduction of

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bulb blackening. In 1924, Marvin Pipkin, an American chemist, patented a process for frosting the inside of lamp bulbs without weakening

them, and in 1947, he p atented a process for coating the inside o f lamps with silica.

In 1930 , HungarianImre Brd y filled lamps with krypton gas in lieu of argon. He used krypton and/or xenon filling of bulbs. Since the new

gas was expensive, he developed a process with his colleagues to obtain krypton from air. Production of krypton filled lamps based on

his invention started atAjka in 1937, in a factory co-designed by Polnyi and Hungarian-born physicist Egon Orowan.[34]

By 1964 , improvements in efficiency and production of incandescent lamps had reduced the cos t of providing a g iven quantity of light by

a factor of thirty, compared with the cost at introduction of Edison's lighting system [35]

Consumption of incandescent light bulbs g rew rapidly in the United States. In 1885, an estimated 300,00 0 ge neral lighting service lampswere sold, all with carbon filaments. When tungsten filament were introduced, there were about 50 million lamp sockets in the United

States. In 1914, 88.5 million lamps were used , (only 15% with carbon filaments), a nd by 1945, annual sales o f lamps were 795 million

(more than 5 lamps per person per year).[36]

Cartels

Main article: Phoebus cartel

Between 1924 and 1939, the international market for incandescent light bulbs was co ntrolled by the Phoebus cartel, which dictated

wholesale prices and whose members controlled most of the world market for lamps.[citation needed]

Eff iciency and environmental impactApproximately 90% of the power consumed by an incandescent light bulb is emitted as heat, rather

than as v isible light.[37]

The e ffectiveness o f an electric lighting so urce is de termined by two factors, the relative visibility of

electromagnetic radiation, and the rate a t which the so urce converts electric power into electromagnetic

radiation.

Luminous efficacy of a light source is a ratio o f the v isible light energy emitted (the luminous flux) to the

total power input to the lamp.[38] Visible light is measured in lumens, a unit which is defined in part by

the differing sensitivity of the human eye to different wavelengths of light. Not all wavelengths of visible

electromagnetic energy a re equally effective a t stimulating the human eye ; the luminous efficacy of

radiant energy is a mea sure of how well the d istribution of energy matches the percep tion of the eye.

The max imum efficacy p ossible is 683 lm/W for monochromatic green light at 555 nanometres

wavelength, the peak sensitivity of the human eye. For white light, the maximum luminous efficacy is

around 240 lumens per watt, but the exact value is not unique because the human eye can perceive

many different mixtures of visible light as "white".

The chart below lists values o f overall luminous efficacy a nd efficiency for several types of ge neral

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Xenon Halogen Lamp (105W) with an E27 base, intendedfor direct replacement of anon-halogen bulb

, , , .

chart in the article on luminous efficacy compares a broader array of light sources to one another.

TypeOverall luminous

efficiency

Overall luminous

efficacy (lm/W)

40 W tungsten incandescent 1.9% 12.6[39]



glass halogen 2.3% 16

quartz halogen 3.5% 24

high- temperature incandescent 5.1% 35[40]

ideal black-body radiator at 4000 K (or a class K

star likeArcturus)7.0% 47.5[41]

ideal blackbody radiator at 7000 K (or a class F

star like Procyon)14% 95[41]

ideal monochromatic 555 nm (green) source 100% 683[42]

Unfortunately, the spectrum emitted by a blackbody radiator doe s not match the sensitivity characteristics o f the human eye. Tungsten

filaments radia te mostly infrared radiation at temperatures where they remain solid (below 3683 kelvins / 3410 C / 6,170 F). Donald L.

Klipstein expla ins it this way: "An ideal thermal radiator produces visib le light most efficiently at temperatures around 6300 C (6600 K or

11,500 F). Even at this high temperature, a lot of the radiation is either infrared or ultraviolet, and the theoretical luminous efficiency is 95

lumens per watt."[40] No known material can be used as a filament at this ideal temperature, which is hotter than the sun's surface. An

upper limit for incandescent lamp luminous e fficacy is a round 52 lumens per watt, the theoretical va lue emitted by tungsten at its melting

point.[35]

For a give n quantity of light, an incandescent light bulb produces more hea t (and consumes more power) than a fluorescent lamp.

Incandescent lamps' heat output increases load on air conditioning in the summer, but the heat from lighting can contribute to building

heating in cold weather.

[43]

High-quality halogen incandescent lamps have higher efficacy, which will allow a 60- watt bulb to provide nearly as much light as a non-

halogen 100-watt bulb. Also, a lower-wattage halogen lamp can be designed to produce the same amount of light as a 60-watt non-

halogen lamp, but with much longer life.

Many light sources, such as the fluorescent lamp , high-intensity discharge lamps and LED lamps offer higher efficiency, and some have

been designed to be retrofitted in existing fixtures. These device s produce light by luminescence, instead of heating a filament to

incandescence. These mechanisms produce discrete spectral lines and so don't have the broad "tail" of wasted invisible infrared

emissions p roduced by incandescent emitters. By careful selection of which electron energy leve l transitions are used, the sp ectrum

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emitted can be tuned to either mimic the ap pearance of incandescent sources o r else p roduce different color temperatures of white for

visible light.

Cost of lighting

See also:Architectural lighting design

The initial cost of an incandescent bulb is small compa red to the cost of the energy it uses over its lifetime. A comparison of

incandescent lamp operating cost with other light sources must consider the luminous efficacy p roduced b y each lamp. The co mparison

must include illumination requirements, ca pital cost of the lamp, labor co st to replace lamps, various depreciation factors for light output

as the lamp ages, effect of lamp operation on heating and air conditioning systems, and energy consumption as well.[citation needed]

Measures to ban its use

Main article: Phase-out of incandescent light bulbs

Due to the higher energy usage of incandescent light bulbs in comparison to more energy efficient alternatives, such as compact

fluorescent lamps and LED lamps, many go vernments have introduced measures to ban their use [44], by setting minimum efficacy

standards higher than can be achieved by general service lamps. However, there has been much resistance to these policies owing to

the low cost of incandesce nt bulbs, the instant availability of light, and p ossible ill health effects including the p roblems o fmercury

contamination with CFLs. Varying and unpredictable quality of current CFLs and LED lamps adds to the resistance.

Efforts to improve ef ficiency

Due to the measures noted ab ove, there have been recent efforts to improve the efficiency of incandesce nts. In 2007, the consumer

lighting division ofGeneral Electric announced a "high efficiency incandescent" (HEI) lamp project, which they claimed would ultimately be

as much as four times more efficient than current incandesce nts, a lthough their initial p roduction goal was to b e a pproximately two times

more efficient.[45][46] The HEI program was q uietly terminated in 2008 due to slow progress. [47][48]

U.S. Department of Energy research at Sandia National Laboratories initially indicated the potential for dramatically improve d e fficiency

from a photonic lattice filament.[45][49] However, later work indicated that initially promising results were in error. [50]

Prompted by U.S. legislation mandating increase d bulb e fficiency by 2012, new "hybrid" incandescent bulbs have been introduced by

Philips. The "Haloge na Energy Saver" incandesce nt is 30 pe rcent more efficient than traditional des igns, using a special chamber to

reflect formerly wasted heat back to the filament to provide add itional lighting power.[51]

Construction

Incandescent light bulbs consist of a glass enclosure (the envelo pe, o r bulb) with a filament of tungsten wire inside the bulb, through

which an electric current is pa ssed. Contact wires a nd a base with two (or more) conductors provide electrical connections to the filament.

Incandescent light bulbs usually contain a stem or g lass mount anchored to the bulb's base that allows the electrical contacts to run

through the e nvelope without gas/air leaks. Small wires embedded in the stem in turn support the filament and/or its lead wires. The bulb

is filled with an inert as such as ar on to reduce eva oration and revent oxidation of the filament.PDFmyURL.com
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An electric current heats the filament to typically 2,000 to 3,300 K (3,140 to 5,480 F)), well below tungsten's melting point of 3,695 K

(6,191 F). Filament temperatures dep end on the filament type, shape , siz e, and amount of current drawn. The hea ted filament emits light

that approximates a continuous spectrum. The useful part of the emitted energy is visible light, but most energy is give n off as heat in the

near- infrared wavelengths.

Three-way light bulbs have two filaments and three conducting contacts in their bases. The filaments share a common ground, and can

be lit separately or together. Common wattages include 3070100, 50100150, and 100200300, with the first two numbers referring

to the individual filaments, and the third giving the combined wattage .

While most light bulbs have clear or frosted glass, other kinds are also produced, including the various colors used for Christmas tree

lights and other decorative lighting. Neodymium-containing glass is sometimes used to provide a more natural-appearing light.

1. Outline of Glass bulb

2. Low pressure inert gas (argon, neon, nitrogen)

3. Tungsten filament4. Contact wire (goes out of stem)

5. Contact wire (goes into stem)

6. Suppo rt wires

7. Stem (glass mount)

8. Contact wire (goes out of stem)

9. Cap (sleeve)

10. Insulation (vitrite)

11. Electrical contact

Many arrangements of electrical contacts are used. Large lamps may have a screw base (one o r more contacts at the tip, one at the

shell) or a bayonet base (one or more contacts on the base, shell used as a contact or used only as a mechanical support). Some

tubular lamps have an electrical contact at either end. Miniature lamps may have a wedge base and wire contacts, and some automotive

and sp ecial p urpose lamp s have screw terminals for connection to wires. Contacts in the lamp socket a llow the e lectric current to pass

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through the base to the filament. Power ratings for incandescent light bulbs range from about 0.1 watt to about 10,000 watts.

The glass bulb of a general service lamp can reach temperatures between 200 and 260 C (392 and 500 F). Lamps intended for high

power operation or used for heating purposes will have envelopes made of hard glass or fused quartz .[35]

Manufacturing

Early lamps were laboriously hand-assembled; however, after automatic machinery was developed the cost of lamps fell.

In manufacturing the glass b ulb, a type of "ribbon machine" is used . A continuous ribbon of glass is passed a long a conveyor belt,

heated in a furnace, and then blown by precisely aligned air nozzles through holes in the conveyor belt into molds. Thus the glass bulbsare crea ted. After the bulbs a re blown, and cooled, they a re cut off of the ribbon machine. A typical machine of this sort produces 50,0 00

bulbs per hour.[52] The filament and its supports are assembled on a g lass s tem, which is fused to the bulb. The air is pumped out of the

bulb, and the evacuation tube in the stem press is sealed by a flame. The bulb is then inserted into the lamp base , and the whole

assembly tested.

Filament

The first successful light bulb filaments were made of carbon (from carbonized paper or bamboo). Early carbon filaments had a negative

temperature coefficient of resistance -- as they got hotter, their electrical resistance decreased. This made the lamp sensitive to

fluctuations in the power supp ly, since a small increase of voltage would cause the filament to heat up, reducing its resistance andcausing it to draw eve n more power and heat even further. In the "flashing" process, ca rbon filaments were hea ted by current passing

through them, while in an evacuated vesse l containing hydrocarbon (gasoline) vapor. The carbon deposited by this treatment improved

the uniformity and strength of filaments, and their efficiency. A metallized or graphitized filament was first heated in a high-temperature

oven before flashing and lamp assemb ly; this transformed the carbon into g raphite, which further strengthened and smoothed the filament,

and as a byproduct had the advantage of changing the lamp to a positive temperature coefficient like a metallic conductor. This helped

stabilize power consumption, temperature and light output aga inst minor variations in supply voltage.

In 1902, the Siemens company developed a tantalum lamp filament. These lamps were more efficient than even graphitized ca rbon

filaments and could operate at higher temperatures. Since the metal had a lower resistivity than carbon, the tantalum lamp filament was

quite long a nd required multiple internal supports. The me tal filament had the property of g radually shortening in use; the filaments were

installed with large loops that tightened in use. This made lamps in use for several hundred hours quite fragile.[53] Metal filaments had theproperty of breaking and re-welding, though this would usually decrease resistance a nd shorten the life of the filament. General Electric

bought the rights to use tantalum filaments and produced them in the United States until 1913.[54]

From 1898 to around 1905, osmium was also used as a lamp filament in Europe, but the metal was so expensive that used broken

lamps co uld be returned for part credit.[55] It could not be made for 110 V or 220 V so several lamps were wired in series for use on

standard voltage circuits.

In 1906, the tungsten filament was introduced. Tungsten metal was initially not available in a form that allowed it to be drawn into fine

wires. Filaments made from sintered tungsten powder were quite fragile. By 1910, a proce ss was developed by William D. Coolidge at

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13/22

Filament of a burnt-out 50-watt incandescentlightbulb in an SEM in stereoscopic mode,presented as an anaglyph image.

Filament of a 50-watt incandescent lightbulb inan SEM in stereoscopic mode, presented as ananaglyph image.

Theatrical, photographic, and projection lamps may have a useful life of only a few

hours, trading life e xpectancy for high output in a compact form. Long-life general

service lamp s have lower efficiency but are used where the cost of changing the

lamp is high compared to the value of energy used.

Filament notching describes another phenomenon that limits the life of lamps. Lamps

operated on direct current develop random stair-step irregularities on the filament

surface, reducing the cross section and further increasing heat and evaporation of

tungsten at these points. In small lamps operated on direct current, lifespan may be

cut in half compared to AC operation. Different alloys of tungsten and rhenium can be

used to counteract the effect.[60][61]

If a light bulb envelope leaks, the hot tungsten filament reacts with air, yield ing an

aerosol of brown tungsten nitride , brown tungsten dioxide, violet-blue tungsten

pentoxide, and yellow tungsten trioxide that then deposits on the nearby surfaces or

the bulb interior.

Bulb blackening

In a conventional lamp, the evaporated tungsten eventually condenses on the inner

surface of the glass envelope, d arkening it. For bulbs that contain a vacuum, thedarkening is uniform across the e ntire surface of the envelope. When a filling of inert

gas is used, the evaporated tungsten is carried in the thermal convection currents of

the ga s, de positing preferentially on the uppermost part of the enve lope and

blackening just that portion of the envelope. An incandescent lamp that gives 93% or less of its initial light output at 75% of its rated life is

regarded as unsatisfactory, when tested according to IEC Publication 60064 . Light loss is due to filament evap oration and bulb

blackening.[62] Study o f the p roblem of bulb b lackening led to the discovery o f the Edison effect, thermionic emission and invention of the

vacuum tube.

A very small amo unt of water vapor inside a light bulb can significantly affect lamp da rkening. Water vapor dissociates into hydroge n and

oxyge n at the hot filament. The oxyge n attacks the tungsten metal, and the resulting tungsten oxide p articles travel to coole r parts of the

lamp. Hydrogen from water vapor reduces the oxide, reforming water vapor and continuing this water cycle .[36]

The equivalent of a dropof water distributed o ver 500,00 0 lamps will significantly increase darkening.[35] Small amounts of substances such as zirconium are

placed within the lamp as a getterto react with any oxyg en that may bake out of the lamp components during operation.

Some o ld, high- powered lamps used in theater, projec tion, searchlight, and lighthouse se rvice with heavy, sturdy filaments contained

loose tungsten powder within the envelope. From time to time, the operator would remove the bulb and shake it, allowing the tungsten

powder to scrub off most of the tungsten that had conde nsed o n the interior of the envelope , removing the b lackening and brightening the

lamp again.[63]

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Close-up of a tungsten filamentinside a halogen lamp. The two ring-shaped structures left and right arefilament supports.

Comparison of eff icacy by power (120

volt lamps)[citation needed]

Power (W) Output (lm) Efficacy (lm/W)

5 25 5

15 110 7.3

25 200 8.0

Halogen lamps

Main article: Halogen lamp

The halogen lamp reduces uneven evaporation of the filament and darkening of the envelope

by filling the lamp with a halogen gas at low pressure, rather than an inert gas. The halogen

cycle increases the lifetime of the b ulb and p revents its darkening by redepo siting tungsten from

the inside of the bulb b ack o nto the filament. The haloge n lamp can operate its filament at a

higher temperature than a standard g as filled la mp of similar power without loss of operating life.

Incandescent arc lamps

A variation of the incandescent lamp did not use a hot wire filament, but instead used a n arc

struck on a spherical bead electrode to produce heat. The electrode then became incandescent,

with the arc contributing little to the light produced. Such lamps were used for projection or

illumination for scientific instruments such as microscopes. These arc lamps ran on relatively low

voltages and incorporated tungsten filaments to start ionization within the envelope . They

provided the intense concentrated light of an arc lamp but were easier to operate. Developed

around 1915, these lamps were displaced by mercury and xenon arc lamps.[64][65][66]

Electrical characteristicsIncandescent lamps are nearly pure resistive loads with a power factorof 1. This means the ac tual po wer consumed (in watts) and the

apparent power (in volt-amperes) are equal. The actual resistance of the filament is temperature-dependent. The cold resistance of

tungsten-filament lamps is about 1/15 the hot-filament resistance when the lamp is operating. For example, a 100- watt, 120-volt lamp has

a resistance of 144 ohms when lit, but the cold resistance is much lower (about 9.5 ohms). [35][67] Since incandescent lamps are resistive

loads, simple triac dimmers can b e used to control brightness. Electrical contacts may carry a "T " rating symbol indicating that they are

designed to control circuits with the high inrush current characteristic of tungsten lamps. For a 100- watt, 120- volt general- service lamp, the

current stabilizes in about 0.10 seconds, and the lamp reaches 90% of its full brightness after about 0.13 seconds.[68]

Power

Incandescent light bulbs a re usually marketed according to the electrical powerconsumed.

This is measured in watts and depends mainly on the resistance of the filament, which in

turn depends mainly on the filament's length, thickness, and material. For two bulbs of the

same voltage, type, color, and clarity, the higher-powered bulb gives more light.

The table shows the ap proximate typical output, in lumens, of standard incandescent light

bulbs a t various powers. Note that the lumen values for "soft white" bulbs will generally be

slightly lower than for standard bulbs a t the sa me po wer, while clear bulbs will usually emit

[citation needed]

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40-watt lightbulbs withstandard E10,E14 and E27Edison screwbase

The double-contact bayonetcap on anincandescentbulb

Available in numerous spo t and flood be am spreads. Like all light bulbs, the number represents the d iameter of the bulb in 18 of an

inch. Therefore, a PAR 16 is 2 in in diameter, a PAR 20 is 2.5 in in diameter, PAR 30 is 3.75 in and a PAR 38 is 4.75 in in diameter.

Multifacet ed reflector (MR)

HIR

"HIR" is a GE designation for a lamp with an infrared reflective coa ting. Since less heat escap es, the filament burns hotter and more

efficiently.[69] The Osram designation for a similar coating is "IRC".[70]

Lamp basesVery small lamps may have the filament support wires extended through the base of the lamp, and can be directly

solde red to a p rinted c ircuit board for connections. Some reflector-type lamps include screw terminals for connection

of wires. Most lamps have metal bases that fit in a socket to suppo rt the lamp and co nduct current to the filament

wires. In the late 19th century, manufacturers introduced a multitude of incompatible lamp bases. General Electric

introduced s tandard base sizes for tungsten incandescent lamps under the Mazda trademark in 1909. This standard

was soon adopted across the United States, and the Mazda name was used by many manufacturers under license

through 1945. Today most incandesce nt lamps for general lighting service use an Edison screw in candelabra,

intermediate, or standard or mogul sizes, or double contact bayonet base. Bayonet base lamps are frequently

used in automotive lamps to resist loosening due to vibration. A bipin base is often used for halogen or reflector

lamps.Lamp bases may be secured to the bulb with a cement, or by mechanical crimping to indentations molded into the

glass bulb.

Miniature lamps used for some automotive lamps or decorative lamps have wedge bases that have a partial plastic

or even co mpletely glass base. In this case, the wires wrap around to the outside of the bulb, where they press

aga inst the contacts in the socke t. Miniature Christmas bulbs use a p lastic wedge base as well.

Lamps intended for use in optical sys tems (such as film projectors, microscop e illuminators, or stage lighting

instruments have bases with alignment features so that the filament is positioned accurately within the optical system.

A screw-base lamp may have a random orientation of the filament when the lamp is installed in the socke t.

Voltage, light output, and lifetime

See also: Lamp rerating

Incandescent lamps are very sensitive to changes in the supply voltage. These characteristics are of great practical

and economic importance.

For a supply voltage Vnear the rated voltage o f the lamp:

Light output is approximately p roportional to V3.4

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Power consumption is approximately p roportional to V1.6

Lifetime is approximately proportional to V16

Color temperature is approximately proportional to V0.42[71]

This means that a 5% reduction in operating voltage will more than double the life of the bulb, a t the expense of reducing its light output

by about 20%. This may be a ve ry accep table trade off for a light bulb that is in a difficult-to-access loca tion (for example, traffic lights or

fixtures hung from high ceilings). Long- life bulbs take advantage of this tradeoff. Since the value o f the e lectric power they consume is

much more than the value of the lamp, general service lamps emphasize efficiency over long operating life. The objective is to minimize

the cost of light, not the cost of lamps.[35]

The relationships above are valid for only a few percent change of voltage around rated conditions, but they do indicate that a lamp

operated at much lower than rated vo ltage could last for hundreds of times longer than at rated conditions, alb eit with greatly reduced

light output. The Centennial Light is a light bulb that is accep ted by the Guinness Book of World Records as having been burning almost

continuously at a fire station in Livermore, California, since 1901. However, the bulb is p owered b y only four watts. A similar story can be

told of a 40-watt bulb in Texas that has bee n illuminated since Sep tember 21, 1908. It once reside d in an opera house where notable

celeb rities stopped to take in its glow, but is now in an area museum.[72]

In flood lamps used forphotographic lighting, the tradeoff is made in the other direction. Compared to general- service bulbs, for the same

power, these bulbs produce far more light, and (more importantly) light at a higher color temperature, at the expense of greatly reduced

life (which may be as short as two hours for a type P1 lamp). The upper temperature limit for the filament is the melting point of the metal.

Tungsten is the metal with the highest melting point, 3,695 K (6,191 F). A 50- hour- life projection bulb, for instance, is designed to ope rateonly 50 C (122 F) b elow that melting point. Such a lamp may achieve up to 22 lumens per watt, compared with 17.5 for a 750- hour

general service lamp.[35]

Lamps de signed for different voltages have different luminous efficacy. For examp le, a 100- watt, 120-volt lamp will produce about 17.1

lumens per watt. A lamp with the same rated lifetime but designed for 230 V would p roduce only around 12.8 lumens per watt, and a

similar lamp designed for 30 volts (train lighting) would produce as much as 19.8 lumens pe r watt.[35] Lower voltage lamps have a thicker

filament, for the same power rating. They can run hotter for the same lifetime before the filament evaporates.

The wires used to support the filament make it mechanically stronger, but remove heat, creating another tradeoff between efficiency and

long life. Many general-service 120-volt lamps use no additional support wires, but lamps designed for " rough service" or "vibration

service" may have as many as five. Low-voltage lamps have filaments made of heavier wire and do not require additional support wires.

Very low voltages are inefficient since the lead wires would conduct too much heat away from the filament, so the p ractical lower limit for

incandescent lamps is 1.5 volts. Very long filaments for high voltages are fragile, and lamp bases become more d ifficult to insulate, so

lamps for illumination are not made with rated vo ltages over 300 volts.[35] Some infrared heating elements are made for higher voltages,

but these use tubular bulbs with widely separated terminals.

Health issues

Although some sources cla im fluorescent lighting ca uses more health problems than incandescent lighting (see Light sensitivity and Over-

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Energy portal

illumination for discussion), more resea rch needs to be done in this field. According to the European Commission Scientific Committee on

Emerging and Newly Identified Health Risks (SCENIHR) in 2008 , the only p roperty of compact fluorescent lamps that could p ose an

added hea lth risk is the ultraviolet and b lue light emitted by such devices . The worst that can happ en is that this radiation could

aggravate symptoms in people who already suffer rare skin conditions that make them excep tionally sensitive to light. They also stated

that more research is needed to establish whether compact fluorescent lamps constitute any higher risk than incandescent lamps.[73]

Radio interference

Incandescent bulbs do not produce significant radio frequency interference, a concern with many other light sources, such as most LED

and fluorescent lamps.

See also

Lamp rerating

Centennial Light

Flash (photography) and discussion of flashbulbs

Fluorescent lamp

Lava lamp

Lightbulb joke s

Longest-las ting light bulbs

Light fixture

List of light sources

MR16 (a popular style of halogen lamp)

Over-illumination

Photometry (optics) Main Photometry/Radiometry a rticle expla ins technical terms

Spectrometer

Lampshade

References

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20 . ^Lodygin US Patent No. 57500 2

21. ^ Hans-Christian Rohde: Die Gbel-Legende Der Kampf um die Erfindung der Glhlampe. Zu Klampen, Springe 2007, ISBN 978-3-86674-

006-8 (german, dissertation)

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26 . ^ R.C. Chirnside. Sir Jo seph Wilso n Swan FRS The Literary and Philos ophical Society of Newcastle upon Tyne 1979 .

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35. ^ abcdefghijkIncandescent Lamps, Publication Number TP-110, General Electric Company, Nela Park, Cleveland, OH (196 4) pg. 3

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88173-378-4 page 37, table 2-1

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37. ^ page 23, table.

38 . ^ IEEE Std. 100 definition of "lum inous efficacy" pg. 647

39. ^ abcKeefe, T.J. (2007). "The Nature of Light" . Retrieved 200 7-11-0 5.

40. ^ ab Klipstein, Donald L. (199 6). "The Great Internet Light Bulb Book, Part I" . Retrieved 200 6-0 4-16.

41. ^ abBlack body visible s pectrum

42. ^ See luminosity function.

43. ^ Prof. Peter Lund, Helsinki University o f Technolo gy, [2] [dead link] on p. C5 in Helsingin Sanomat Oct. 23, 200 7.

44. ^"Is Environmentalism Really Working?: Germany's Eco-Trap" (in English). Der Spiegel. 17 March 2010 . Retrieved 20 March 20 11.

45. â

b

Daley, Dan (February 2008 ). "Incandescent's No t-So- Dim Future". Projection Lights and Staging News (PLSN) (TimelessComm unications Co rp.) 09 (1): p. 46.

46 . ^GE Announces Advancement in Incandescent Technolo gy; New High-Efficiency Lamps Targeted for Market by 20 10

47. ^Why the brightest idea needs tinkering

48 . ^The Incandescent Bulb Heads O ffstage After Century-Long Performance

49 . ^"Proposed Bulb Ban Causes Chain Reaction" . Projection Lights and Staging News (PLSN) Online . January 2008 .

50 . Êditorial note later added to July 7, 2003 pres s release

51. ^ Broydo Vestel, Leora (July 6, 2009). "Incandescent Bulbs Return to the Cutting Edge" . The New York Times . Retrieved 2009 -0 7-06 .

52. ^Light Bulb: How Products are Made

53. ^ I. C. S. Reference Library Volume 4B, Scranton, International Textbook Co mpany , 190 8, no ISBN

54. ^GE Tantalum Filam ent 25W of American Design

55. ^"The Osmium Filament Lamp"56 . ^ Chapter 2 The Potassium Secret Behind Tungsten Wire Production

57. ^ Jo hn Kaufman (ed.), IES Lighting Handbook 1981 Reference Volume , Illuminating Engineering Society of No rth America, New York, 1981 ISBN

0-87995-007-2 page 8-6

58 . ^ Burgin. Lighting Research and Technolo gy 1984 16.2 6172

59 . ^ Hunt, Robert (20012006). "Glass Blowing for Vacuum Devices - Lamp Autopsy" . Teralab. Retrieved 2007- 05- 02.

60 . ^Tos hiba Lighting Products Miniature Lamp Characteristics . Retrieved 23 March 2008 .

61. ^ Jo hn Kaufman (ed.), IES Lighting Handbook 1981 Reference Volume , Illuminating Engineering Society of No rth America, New York, 1981 ISBN

0-87995-007-2 page 8-9

62 . ^ IEC 60064 Tungsten filament lamps for domestic and similar general lighting purposes.

63 . ^ Jo hn Kaufman (ed.), IES Lighting Handbook 1981 Reference Volume , Illuminating Engineering Society of No rth America, New York, 1981 ISBN

0-87995-007-2 page 8-1064 . Încandescent arc lamps retrieved June 16, 200 8

65 . ^ G. Arncliffe Percival, The Electric Lamp Industry, Sir Isaac Pitman and Sons, Ltd. Londo n, 1920 pp. 7374, available from the Internet Archive

66 . ^ S. G. Starling,An Introduction to Technical Electricity', McMillan and Co., Ltd., London 1920, pp. 9798, available at the Internet Archive, good

schematic diagram of the Pointolite lamp

67 . ^ Ediso n's res earch team was aware of the large negative temperature coefficient of resistance of pos sible lam p filament materials and

worked extensively during the period 18781879 o n devising an automatic regulator orballastto s tabilize current. It wasn't until 1879 that it

was realized a s elf-limiting lamp could be built. See Friedel and Israel Edison's Electric Light pages 2931

68 . ^ page 23, 24

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69 . ^Lighting Glossary

70 . ^Osram IRC Saver calculator

71. ^Donald G. Fink and H. Wayne Beaty,Standard Handbook for Electrical Engineers, Eleventh Edition , McGraw-Hill, New York, 1978 , ISBN 0-0 7-

020974-X, pg 22-8

72. ^Magazine Online

73. ^"Energy-Saving Lamps & Health" . GreenFacts Website. Retrieved January 20, 20 10.

External links

Museum of Electric Lamp TechnologyHowstuffworks - "How Light Bulbs Work"

Light Source Spectra 60 W- 100 W Incandescent light bulb spectra

Halogen Light Bulbs Base Identification

Light Bulbs - Lamps and Tubes - Lamp Bases Explained [dead link]

The Perfection of the Electric Light Bulb background and experiment

Incandescent Light Bulb's Bulb and Base Types Explained

Examples of how color temperature of light bulbs affect our surroundings

An brief article explaing the light bulb - "The Composition of the Light Bulb"

The history of the light bulb

BanTheBulb.Org energy efficiency campaign

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Categories: Discovery and invention controversies | English inventions | Incandescent light bulbs | Light sources | Thomas Edison

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