The 15 kW xenon short-arc lamp used in the IMAX projection system.

A mercury arc lamp from a fluorescence microscope.

"Arc lamp" or "arc light" is the general term for a class of lamps that produce light by an electric arc (also called a voltaic arc). The lamp consists of two electrodes, first made from carbon but typically made today of tungsten, which are separated by a gas. The type of lamp is often named by the gas contained in the bulb; including neon, argon, xenon, krypton, sodium, metal halide, and mercury, or by the type of electrode as in carbon-arc lamps. The common fluorescent lamp is a low-pressure mercury arc lamp.^[1]

Operation[link]

An arc is the discharge that occurs when a gas is ionized. A high voltage is pulsed across the lamp to "ignite" or "strike" the arc, after which the discharge can be maintained at a lower voltage. The "strike" requires an electrical circuit with an igniter and a ballast. The ballast is wired in series with the lamp and performs two functions.

First, when the power is first switched on, the igniter/starter (which is wired in parallel across the lamp) sets up a small current through the ballast and starter. This creates a small magnetic field within the ballast windings. A moment later the starter interrupts the current flow from the ballast, which has a high inductance and therefore tries to maintain the current flow (the ballast opposes any change in current through it); it cannot, as there is no longer a 'circuit'. As a result, a high voltage appears across the ballast momentarily - to which the lamp is connected, therefore the lamp receives this high voltage across it which 'strikes' the arc within the tube/lamp. The circuit will repeat this action until the lamp is ionized enough to sustain the arc.

When the lamp sustains the arc, the ballast performs its second function, to limit the current to that needed to operate the lamp. The lamp, ballast and igniter are rated matched to each other; these parts must be replaced with the same rating as the failed component or the lamp will not work.

The colour of the light emitted by the lamp changes as its electrical characteristics change with temperature and time. Lightning is a similar principle where the atmosphere is ionized by the high potential difference (voltage) between earth and storm clouds.

The temperature of the arc in an arc lamp can reach several thousand degrees Celsius. The outer glass envelope can reach 500 degrees Celsius, therefore before servicing one must ensure the bulb has cooled sufficiently to handle. Often, if these type of lamps are turned off or lose their power supply, one cannot restrike the lamp again for several minutes (called cold restrike lamps). However, some lamps (mainly fluorescent tubes/energy saving lamps) can be restruck as soon as they are turned off (called hot restrike lamps).

Carbon arc lamp[link]

A carbon arc lamp, cover removed, on the point of ignition. This model requires manual adjustment of the electrodes

An electric arc, demonstrating the “arch” effect.

Self-regulating arc lamp proposed by William Edwards Staite and William Petrie in 1847

In popular use, the term arc lamp means carbon arc lamp only. In a carbon arc lamp, the electrodes are carbon rods in free air. To ignite the lamp, the rods are touched together, thus allowing a relatively low voltage to strike the arc. The rods are then slowly drawn apart, and electric current heats and maintains an arc across the gap. The tips of the carbon rods are heated to incandescence, creating light. The rods are slowly burnt away in use, and the distance between them needs to be regularly adjusted in order to maintain the arc. Many ingenious mechanisms were invented to effect this automatically, mostly based on solenoids. In the simplest form (which was soon superseded by more smoothly acting devices) the electrodes are mounted vertically. The current supplying the arc is passed in series through a solenoid attached to the top electrode. If the points of the electrodes are touching (as in start up) the resistance falls, the current increases and the increased pull from the solenoid draws the points apart. If the arc starts to fail the current drops and the points close up again.

History[link]

The concept of carbon-arc lighting was first demonstrated by Sir Humphry Davy in the early 19th century (1802, 1805, 1807 and 1809 are all mentioned), using charcoal sticks and a 2000-cell battery to create an arc across a 4-inch (100 mm) gap. He mounted his electrodes horizontally and noted that, because of the strong convection flow of air, the arc formed the shape of an arch. He coined the term "arch lamp", which was contracted to "arc lamp" when the devices came into common usage.^[2]

Carbon-arc lighting in the U.S.[link]

In the United States, there were attempts to produce arc lamps commercially after 1850 but the lack of a constant electricity supply thwarted efforts. Thus electrical engineers began focusing on the problem of improving Faraday's dynamo. The concept was improved upon by a number of people including William Staite and Charles F. Brush. It was not until the 1870s that lamps such as the Yablochkov candle were more commonly seen. In 1877, the Franklin Institute conducted a comparative test of dynamo systems. The one developed by Brush performed best, and Brush immediately applied his improved dynamo to arc-lighting an early application being Public Square in Cleveland, Ohio, on April 29, 1879.^[3] In 1880, Brush established the Brush Electric Company.

The harsh and brilliant light was found most suitable for public areas, such as Cleveland's Public Square, being around 200 times more powerful than contemporary filament lamps.

The usage of Brush electric arc lights spread quickly. Scientific American reported in 1881 that the system was being used in:^[4]

• 800 lights in rolling mills, steel works, shops, etc.
• 1,240 lights in woolen, cotton, linen, silk, and other factories
• 425 lights in large stores, hotels, churches, etc.
• 250 lights in parks, docks, and summer resorts
• 275 lights in railroad depots and shops
• 130 lights in mines, smelting works, etc.
• 380 lights in factories and establishments of various kinds
• 1,500 lights in lighting stations, for city lighting, etc.
• 1,200 lights in England and other foreign countries.
• A total of over 6,000 lights which are actually sold

There were three major advances in the 1880s:

• The arcs were enclosed in a small tube to slow the carbon consumption (increasing the life span to around 100 hours).
• Flame arc lamps were introduced where the carbon rods had metal salts (usually magnesium, strontium, barium, or calcium fluorides) added to increase light output and produce different colours.
• František Křižík invented a mechanism to allow the automatic adjustment of the electrodes.

In the U.S., patent protection of arc-lighting systems and improved dynamos proved difficult and as a result the arc-lighting industry became highly competitive. Brush's principal competition was from the team of Elihu Thomson and Edwin J. Houston. These two had formed the American Electric Company in 1880, but it was soon bought up by Charles A. Coffin, moved to Lynn, Massachusetts, and renamed the Thomson-Houston Electric Company. Thomson remained, though, the principal inventive genius behind the company patenting improvements to the lighting system. Under the leadership of Thomson-Houston's patent attorney, Frederick P. Fish, the company protected its new patent rights. Coffin's management also led the company towards an aggressive policy of buy-outs and mergers with competitors. Both strategies reduced competition in the electrical lighting manufacturing industry. By 1890, the Thomson-Houston company was the dominant electrical manufacturing company in the U.S.^[5] Nikola Tesla received U.S. Patent 447920, "Method of Operating Arc-Lamps" (March 10, 1891), that describes a 10,000 cycles per second alternator to suppress the disagreeable sound of power-frequency harmonics produced by arc lamps operating on frequencies within the range of human hearing.

Around the turn of the century arc-lighting systems were in decline, but Thomson-Houston controlled key patents to urban lighting systems. This control slowed the expansion of incandescent lighting systems being developed by Thomas Edison's Edison General Electric Company. Conversely, Edison's control of direct current distribution and generating machinery patents blocked further expansion of Thomson-Houston. The roadblock to expansion was removed when the two companies merged in 1892 to form the General Electric Company.^[5]

Arc lamps were used in some early motion-picture studios to illuminate interior shots. One problem was that they produce such a high level of ultra-violet light that many actors needed to wear sunglasses when off camera to relieve sore eyes resulting from the ultra-violet light. The problem was solved by adding a sheet of ordinary window glass in front of the lamp, blocking the ultra-violet. By the dawn of the "talkies", arc lamps had been replaced in film studios with other types of lights. In 1915, Elmer Ambrose Sperry began manufacturing his invention of a high-intensity carbon arc searchlight. These were used aboard warships of all navies during the 20th century for signaling and illuminating enemies.^[6] In the 1920s, carbon arc lamps were sold as family health products, a substitute for natural sunlight.^[7]

Arc lamps were superseded by filament lamps in most roles, remaining in only certain niche applications such as cinema projection, followspots, and searchlights. Even in these applications conventional carbon arc lamps are being pushed into obsolescence by xenon arc lamps.

See also[link]

• Electric light
• Léon Foucault
• Graphite
• František Křižík
• Large Format Slide Projector
• Light bulb
• List of light sources
• Manual metal arc welding
• Movie projector
• Walther Nernst
• Photolithography
• Praseodymium
• Stage lighting
• Timeline of lighting technology
• Tesla patents
• Yablochkov candle
• Pavel Yablochkov

References[link]

Bibliography[link]

• Braverman, Harry (1974). Labor and Monopoly Capital. New York: Monthly Review Press. 
• MacLaren, Malcolm (1943). The Rise of the Electrical Industry during the Nineteenth Century. Princeton: Princeton University Press. 
• Noble, David F. (1977). America by Design: Science, Technology, and the Rise of Corporate Capitalism. New York: Oxford University Press. pp. 6–10. 
• Prasser, Harold C. (1953). The Electrical Manufacturers. Cambridge: Harvard University Press. 

External links[link]

Wikimedia Commons has media related to: Arc lamp

• Arc Lamp - Interactive Java Tutorial National High Magnetic Field Laboratory

Look up arc, arc-, or arcs in Wiktionary, the free dictionary.

Arc may refer to:

Mathematics[link]

• Arc (geometry), a segment of a differentiable curve
• Arc (projective geometry), a particular type of set of points of a projective plane
• Arcminute, a measure used for angles, equal to 1/60th of a degree
• "arc-", a prefix sometimes used for an inverse function, specifically trigonometry functions
• A directed edge in graph theory

Optics[link]

• 120° parhelion, relatively rare halo, an optical phenomenon occasionally appearing along with very bright sun dogs
• Infralateral arc, a rare halo, an optical phenomenon appearing similar to a rainbow under a white parhelic circle
• Lower tangent arc, rarely observable halo, an optical phenomenon appearing under and tangent to a 22° halo centred around the sun
• Parry arc, a rare halo, an optical phenomenon which occasionally appears over a 22° halo together with an upper tangent arc
• Subhelic arc, a rare halo that curves upwards from the horizon and touches the tricker arc above the anthelic point
• Supralateral arc, a rare halo, an optical phenomenon often confused with the indeed infrequently appearing 46° halo
• Upper tangent arc, halo, an atmospheric optical phenomenon which appears over and tangent to the 22° halo centred around the sun

Engineering[link]

• Arc chute, a protective device in an electrical circuit breaker
• Arc lamp, a device that produces light by an electric arc
• Arc welding, a method of welding that uses an electric arc to melt the metals together
• Electric arc or voltaic arc, an ongoing plasma discharge (an electric current through a gas), producing light and heat
• Arc or arch, a bowed or curved structure capable of spanning a space while supporting significant weight

Places[link]

• Arc (Savoie), a river of eastern France, tributary of the Isère river
• Arc (Provence), a river of southern France, flowing into the Étang de Berre
• Les Arcs, a ski resort in the French Alps
• Volcanic arc, a chain of volcanoes positioned in an arc shape as seen from above
• Island arc, a type of archipelago composed of a chain of volcanoes which alignment is arc-shaped, and which are situated parallel and close to a boundary between two converging tectonic plates

Biology[link]

• Arc (protein), a name of product of an immediate early gene, also called Arg3.1

Modern culture[link]

• Story arc, an extended or continuing storyline
• Character arc, the status of a character as it unfolds throughout the story
• "Arc", a song by Pearl Jam from Riot Act
• Arc (album), a 1991 live album by Neil Young
• Advance Reading copy or Advance copy

Computing and gaming[link]

• Arc (programming language), a Lisp dialect designed by Paul Graham
• ARC (file format), a file extension for archive files
• arc, the command-line interface for ArcInfo
• Arc System Works, a video game developer
• ARC International, a developer of configurable microprocessor technology now owned by Synopsys

Other[link]

• Aramaic language (ISO 639-2/3 language code), a Semitic language
• Arc @ UNSW, the principal student organisation at the University of New South Wales
• Arc of the United States, a charitable organization
• Joan of Arc (c. 1410–1431), nicknamed "The Maid of Orléans" (French: Jeanne d'Arc, IPA: [ʒan daʁk]; ca. 1412 – 30 May 1431), is considered a national heroine of France and a Catholic saint
• Prix de l'Arc de Triomphe, a Group 1 flat horse race
• Arc (Bahá'í), a number of administrative buildings for the Bahá'í Faith, located on Mount Carmel in Israel
• Sony Ericsson Xperia Arc, a cellphone

See also[link]

• Ark (disambiguation)
• Arch (disambiguation)
• ARCS (disambiguation)
• ARRC (disambiguation)

This disambiguation page lists articles associated with the same title. If an internal link led you here, you may wish to change the link to point directly to the intended article.

Look up LAMP or lamp in Wiktionary, the free dictionary.

Lamp or LAMP may refer to one of the following:

Lighting[link]

• Oil lamp, the original use of the term
• Kerosene lamp, a lamp burning liquid petroleum
• Lamp (electrical component), a replaceable component that produces light, such as:
  • Arc lamp
  • Fluorescent lamp
  • Gas-discharge lamp
  • Incandescent light bulb, also known as an incandescent lamp
• Lampshade, the part of a luminaire that serves to block direct view of the lamp
• Light fixture, or luminaire, often colloquially known as a lamp
• Signal lamp, a device used for visual communication between ships
• A fuel burning illumination or signal lantern
• A safety lamp or Davy lamp, an explosion-proof lantern used in mining
  • See also Category:Lamps

Music and film[link]

• "Lamp" (song), 1999 Bump of Chicken single
• The Lamp (1986 film), a 1986 horror film
• The Lamp (2011 film), a 2011 family film
• Lamp (advertisement), a 2002 television advertisement directed by Spike Jonze

People with the surname Lamp[link]

• Charles Lamp (1895-1972), Australian politician
• Dennis Lamp (born 1952), American baseball pitcher
• Jeff Lamp (born 1959), American basketball player

LAMP[link]

As an Acronym, LAMP may refer to:

Computing[link]

• LAMP (software bundle), a platform consisting of Linux, Apache, MySQL and Perl/PHP/Python
• Library Access to Music Project, a free music library for MIT students
• LAMP (LAMP.MN), an application used for smartphones to find friends and search locations

Science[link]

• Lyman Alpha Mapping Project, an instrument to be used on the NASA Lunar Reconnaissance Orbiter
• Loop-mediated isothermal amplification, a single tube technique for the amplification of DNA
• Lysosome-associated membrane glycoprotein
  • LAMP1 – Lysosomal-associated membrane protein 1
  • LAMP2 – Lysosomal-associated membrane protein 2
  • LAMP3 – Lysosomal-associated membrane glycoprotein 3
• LAMP, a short-range model output statistics system used in the Nested Grid Model and later the Global Forecast System

Other[link]

• Lutheran Association of Missionaries and Pilots, a cross-cultural ministry organisation
• Loveless Academic Magnet Program, a magnet high school in Montgomery, Alabama
• LAMP Community, a Los Angeles-based nonprofit organization located in Skid Row

See also[link]

• All pages with titles containing "lamp", includes many other forms of lamp
• Lampadarius, also for liturgical uses of lamps
• Stage lighting instruments, a general term for a variety of light sources used for theater and television production

This disambiguation page lists articles associated with the same title. If an internal link led you here, you may wish to change the link to point directly to the intended article.