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59-419: An arclight or arc lamp is a lamp that produces a bright light by generating an electric arc across two electrodes. Arclight , Arc Light or arc light may also refer to: Arc lamp The carbon arc light, which consists of an arc between carbon electrodes in air, invented by Humphry Davy in the first decade of the 1800s, was the first practical electric light . It was widely used starting in

118-656: A motor-generator combo (AC motor powering a DC generator). Even in these applications conventional carbon-arc lamps were mostly pushed into obsolescence by xenon arc lamps , but were still being manufactured as spotlights at least as late as 1982 and are still manufactured for at least one purpose – simulating sunlight in "accelerated aging" machines intended to estimate how fast a material is likely to be degraded by environmental exposure. Carbon arc lighting left its imprint on other film projection practices. The practice of shipping and projecting motion pictures on 2,000-foot reels, and employing "changeovers" between two projectors,

177-401: A straight-line axis; for example, William Sturgeon 's electromagnet of 1824 consisted of a solenoid bent into a horseshoe shape (similarly to an arc spring ). Solenoids provide magnetic focusing of electrons in vacuums, notably in television camera tubes such as vidicons and image orthicons. Electrons take helical paths within the magnetic field. These solenoids, focus coils, surround nearly

236-441: A close approximation of sunlight is needed, for testing materials, paints, and coatings for wear, fading, or deterioration, or, for example, spacecraft materials that are to be exposed to sunlight at orbits closer than Earth's. The arc consists of pure carbon-vapor heated to a plasma state. However, the arc contributes very little of the light output, and is considered non-luminous, as most of its emission occurs in spectral lines in

295-456: 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. Despite this, Wabash, Indiana claims to be the first city ever to be lit with "Brush Lights". Four of these lights became active there on March 31, 1880. Wabash was

354-410: 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

413-412: 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. In

472-563: A small enough city to be lit entirely by 4 lights, whereas the installation at Cleveland's Public Square only lit a portion of that larger city. 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

531-447: A source of high intensity ultraviolet light. The term is now used for gas discharge lamps , which produce light by an arc between metal electrodes through a gas in a glass bulb. The common fluorescent lamp is a low-pressure mercury arc lamp. The xenon arc lamp , which produces a high intensity white light, is now used in many of the applications which formerly used the carbon arc, such as movie projectors and searchlights. An arc

590-475: A uniform magnetic field in a volume of space when an electric current is passed through it. André-Marie Ampère coined the term solenoid in 1823, having conceived of the device in 1820. The French term originally created by Ampère is solénoïde , which is a French transliteration of the Greek word σωληνοειδὴς which means tubular . The helical coil of a solenoid does not necessarily need to revolve around

649-409: Is a simple arc lamp without a regulator, but it has the drawbacks that the arc cannot be restarted (single use) and a limited lifetime of only a few hours. The spectrum emitted by a carbon-arc lamp is the closest to that of sunlight of any lamp. One of the first electric lights, their harsh, intense output usually limited their use to lighting large areas. Although invisible wavelengths were unknown at

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708-405: Is independent of current. Similar analysis applies to a solenoid with a magnetic core, but only if the length of the coil is much greater than the product of the relative permeability of the magnetic core and the diameter. That limits the simple analysis to low-permeability cores, or extremely long thin solenoids. The presence of a core can be taken into account in the above equations by replacing

767-425: Is just air (which behaves much like free space). In that scenario, the full effect of the high permeability material is not seen, but there will be an effective (or apparent) permeability μ eff such that 1 ≤  μ eff  ≤  μ r . The inclusion of a ferromagnetic core, such as iron , increases the magnitude of the magnetic flux density in the solenoid and raises the effective permeability of

826-476: Is the magnetic constant , N {\displaystyle N} the number of turns, I {\displaystyle I} the current and l {\displaystyle l} the length of the coil. Ignoring end effects, the total magnetic flux through the coil is obtained by multiplying the flux density B {\displaystyle B} by the cross-section area A {\displaystyle A} : Combining this with

885-424: Is the magnetic flux density , l {\displaystyle l} is the length of the solenoid, μ 0 {\displaystyle \mu _{0}} is the magnetic constant , N {\displaystyle N} the number of turns, and I {\displaystyle I} the current. From this we get This equation is valid for a solenoid in free space, which means

944-416: 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

1003-414: 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

1062-528: 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

1121-614: The University of British Columbia , Vancouver, Canada, made the Guinness Book of World Records in 1986 and 1993 as the most powerful continuously burning light source at over 300 kW or 1.2 million candle power. 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

1180-401: The permeability of the magnetic path is the same as permeability of free space, μ 0 . If the solenoid is immersed in a material with relative permeability μ r , then the field is increased by that amount: In most solenoids, the solenoid is not immersed in a higher permeability material, but rather some portion of the space around the solenoid has the higher permeability material and some

1239-434: The right hand grip rule for the field around a wire. If we wrap our right hand around a wire with the thumb pointing in the direction of the current, the curl of the fingers shows how the field behaves. Since we are dealing with a long solenoid, all of the components of the magnetic field not pointing upwards cancel out by symmetry. Outside, a similar cancellation occurs, and the field is only pointing downwards. Now consider

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1298-1293: The vector potential , which for a finite solenoid with radius R and length l in cylindrical coordinates ( ρ , ϕ , z ) {\displaystyle (\rho ,\phi ,z)} is A ϕ = μ 0 I π R l [ ζ ( R + ρ ) 2 + ζ 2 ( m + n − m n m n K ( m ) − 1 m E ( m ) + n − 1 n Π ( n , m ) ) ] ζ − ζ + , {\displaystyle A_{\phi }={\frac {\mu _{0}I}{\pi }}{\frac {R}{l}}\left[{\frac {\zeta }{\sqrt {(R+\rho )^{2}+\zeta ^{2}}}}\left({\frac {m+n-mn}{mn}}K(m)-{\frac {1}{m}}E(m)+{\frac {n-1}{n}}\Pi (n,m)\right)\right]_{\zeta _{-}}^{\zeta _{+}},} Where: Here, K ( m ) {\displaystyle K(m)} , E ( m ) {\displaystyle E(m)} , and Π ( n , m ) {\displaystyle \Pi (n,m)} are complete elliptic integrals of

1357-399: The 1870s for street and large building lighting until it was superseded by the incandescent light in the early 20th century. It continued in use in more specialized applications where a high intensity point light source was needed, such as searchlights and movie projectors until after World War II . The carbon arc lamp is now obsolete for most of these purposes, but it is still used as

1416-429: The 1880s: František Křižík invented in 1880 a mechanism to allow the automatic adjustment of the electrodes. 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. In

1475-400: The 1920s, carbon arc lamps were sold as family health products, a substitute for natural sunlight. Arc lamps were superseded by filament lamps in most roles, remaining in only certain niche applications such as cinema projection , spotlights , and searchlights. In the 1950s and 1960s the high-power D.C. for the carbon-arc lamp of an outdoor drive-in projector would typically be supplied by

1534-493: 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 Corporation in 1880, but it was soon bought up by Charles A. Coffin , moved to Lynn, Massachusetts , and renamed

1593-429: The advent of xenon projector lamps, being replaced with single-projector platter systems , though films would continue to be shipped to cinemas on 2,000-foot reels. Solenoid A solenoid ( / ˈ s oʊ l ə n ɔɪ d / ) is a type of electromagnet formed by a helical coil of wire whose length is substantially greater than its diameter, which generates a controlled magnetic field . The coil can produce

1652-525: The anode facing outward to keep from blocking its light output. Since carbon has the highest melting point of any element, it is the only lamp whose blackbody radiation is capable of nearly matching the Sun's temperature of 10,000 degrees Fahrenheit (5500 degrees Celsius), especially when filters are used to remove most of the IR and UV light. The concept of carbon-arc lighting was first demonstrated by Humphry Davy in

1711-602: 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 types 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). The Vortek water-wall plasma arc lamp, invented in 1975 by David Camm and Roy Nodwell at

1770-610: The arc. In 1899, she was the first woman ever to read her own paper before the Institution of Electrical Engineers (IEE). Her paper was "The Hissing of the Electric Arc". The arc lamp provided one of the first commercial uses for electricity, a phenomenon previously confined to experiment, the telegraph, and entertainment. In the United States, there were attempts to produce arc lamps commercially after 1850, but

1829-400: The definition of inductance the inductance of a solenoid follows as A table of inductance for short solenoids of various diameter to length ratios has been calculated by Dellinger, Whittmore, and Ould. This, and the inductance of more complicated shapes, can be derived from Maxwell's equations . For rigid air-core coils, inductance is a function of coil geometry and number of turns, and

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1888-405: The distance from the axis nor on the solenoid's cross-sectional area. This is a derivation of the magnetic flux density around a solenoid that is long enough so that fringe effects can be ignored. In Figure 1, we immediately know that the flux density vector points in the positive z direction inside the solenoid, and in the negative z direction outside the solenoid. We confirm this by applying

1947-422: The early 19th century, but sources disagree about the year he first demonstrated it; 1802, 1805, 1807 and 1809 are all mentioned. Davy used charcoal sticks and a two-thousand- 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

2006-661: The electrical lighting manufacturing industry. By 1890, the Thomson-Houston company was the dominant electrical manufacturing company in the U.S. 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

2065-413: 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. The Yablochkov candle

2124-425: The electrons are forced to enter the anode at the hottest point, generating tremendous amounts of heat that vaporizes the carbon and creates a pit in the anode's surface. This pit is heated from 6000 to 6500 degrees Fahrenheit (3300 to 3600 degrees Celsius, just below its melting point), causing it to glow very brightly with incandescence. Due to this, the electrodes were often placed at right angles from each other with

2183-405: The field is pointing upwards inside the solenoid, so the horizontal portions of loop c do not contribute anything to the integral. Thus the integral of the up side 1 is equal to the integral of the down side 2. Since we can arbitrarily change the dimensions of the loop and get the same result, the only physical explanation is that the integrands are actually equal, that is, the magnetic field inside

2242-416: The field outside must go to zero as the solenoid gets longer. Of course, if the solenoid is constructed as a wire spiral (as often done in practice), then it emanates an outside field the same way as a single wire, due to the current flowing overall down the length of the solenoid. Applying Ampère's circuital law to the solenoid (see figure on the right) gives us where B {\displaystyle B}

2301-1577: The first, second, and third kind. Using: B → = ∇ × A → , {\displaystyle {\vec {B}}=\nabla \times {\vec {A}},} The magnetic flux density is obtained as B ρ = μ 0 I 4 π 1 l ρ [ ( R + ρ ) 2 + ζ 2 ( ( m − 2 ) K ( m ) + 2 E ( m ) ) ] ζ − ζ + , {\displaystyle B_{\rho }={\frac {\mu _{0}I}{4\pi }}{\frac {1}{l\,\rho }}\left[{\sqrt {(R+\rho )^{2}+\zeta ^{2}}}{\biggl (}(m-2)K(m)+2E(m){\biggr )}\right]_{\zeta _{-}}^{\zeta _{+}},} B z = μ 0 I 2 π 1 l [ ζ ( R + ρ ) 2 + ζ 2 ( K ( m ) + R − ρ R + ρ Π ( n , m ) ) ] ζ − ζ + . {\displaystyle B_{z}={\frac {\mu _{0}I}{2\pi }}{\frac {1}{l}}\left[{\frac {\zeta }{\sqrt {(R+\rho )^{2}+\zeta ^{2}}}}\left(K(m)+{\frac {R-\rho }{R+\rho }}\Pi (n,m)\right)\right]_{\zeta _{-}}^{\zeta _{+}}.} On

2360-412: The flux density outside is practically zero since the radii of the field outside the solenoid will tend to infinity. An intuitive argument can also be used to show that the flux density outside the solenoid is actually zero. Magnetic field lines only exist as loops, they cannot diverge from or converge to a point like electric field lines can (see Gauss's law for magnetism ). The magnetic field lines follow

2419-429: The gap. The tips of the carbon rods are heated and the carbon vaporizes. 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 control the distance automatically, mostly based on solenoids . In one of the simplest mechanically-regulated forms (which was soon superseded by more smoothly acting devices)

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2478-430: The imaginary loop c that is located inside the solenoid. By Ampère's law , we know that the line integral of B (the magnetic flux density vector) around this loop is zero, since it encloses no electrical currents (it can be also assumed that the circuital electric field passing through the loop is constant under such conditions: a constant or constantly changing current through the solenoid). We have shown above that

2537-433: The intrinsic inductance and capacitance cannot be done using those for the conventional solenoids, i.e. the tightly wound ones. New calculation methods were proposed for the calculation of intrinsic inductance (codes available at ) and capacitance. (codes available at ) As shown above, the magnetic flux density B {\displaystyle B} within the coil is practically constant and given by where μ 0

2596-549: 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 Edwards Staite  [ de ] 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

2655-460: The lamp. The lamp, ballast, and igniter are rating-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

2714-402: The longitudinal path of the solenoid inside, so they must go in the opposite direction outside of the solenoid so that the lines can form loops. However, the volume outside the solenoid is much greater than the volume inside, so the density of magnetic field lines outside is greatly reduced. Now recall that the field outside is constant. In order for the total number of field lines to be conserved,

2773-782: The magnetic flux density through the centre of the solenoid (in the z direction, parallel to the solenoid's length, where the coil is centered at z =0) can be estimated as the flux density of a single circular conductor loop: Within the category of finite solenoids, there are those that are sparsely wound with a single pitch, those that are sparsely wound with varying pitches (varied-pitch solenoid), and those with varying radii for different loops (non-cylindrical solenoids). They are called irregular solenoids . They have found applications in different areas, such as sparsely wound solenoids for wireless power transfer , varied-pitch solenoids for magnetic resonance imaging (MRI), and non-cylindrical solenoids for other medical devices. The calculation of

2832-465: The magnetic path. This is expressed by the formula where μ eff is the effective or apparent permeability of the core. The effective permeability is a function of the geometric properties of the core and its relative permeability. The terms relative permeability (a property of just the material) and effective permeability (a property of the whole structure) are often confused; they can differ by many orders of magnitude. For an open magnetic structure,

2891-676: The relationship between the effective permeability and relative permeability is given as follows: where k is the demagnetization factor of the core. A finite solenoid is a solenoid with finite length. Continuous means that the solenoid is not formed by discrete coils but by a sheet of conductive material. We assume the current is uniformly distributed on the surface of the solenoid, with a surface current density K ; in cylindrical coordinates : K → = I l ϕ ^ . {\displaystyle {\vec {K}}={\frac {I}{l}}{\hat {\phi }}.} The magnetic field can be found using

2950-420: The solenoid is radially uniform. Note, though, that nothing prohibits it from varying longitudinally, which in fact, it does. A similar argument can be applied to the loop a to conclude that the field outside the solenoid is radially uniform or constant. This last result, which holds strictly true only near the center of the solenoid where the field lines are parallel to its length, is important as it shows that

3009-471: The solenoid, far away from the ends ( l / 2 − | z | ≫ R {\displaystyle l/2-|z|\gg R} ), this tends towards the constant value B = μ 0 N I / l {\displaystyle B=\mu _{0}NI/l} . For the case in which the radius is much larger than the length of the solenoid ( R ≫ l {\displaystyle R\gg l} ),

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3068-656: The symmetry axis, the radial component vanishes, and the axial field component is B z = μ 0 N I 2 ( z + l / 2 l R 2 + ( z + l / 2 ) 2 − z − l / 2 l R 2 + ( z − l / 2 ) 2 ) . {\displaystyle B_{z}={\frac {\mu _{0}NI}{2}}\left({\frac {z+l/2}{l{\sqrt {R^{2}+(z+l/2)^{2}}}}}-{\frac {z-l/2}{l{\sqrt {R^{2}+(z-l/2)^{2}}}}}\right).} Inside

3127-631: The system was being used in: 800 lights in rolling mills, steel works, shops, 1,240 lights in woolen, cotton, linen, silk, and other factories, 425 lights in large stores, hotels, churches, 250 lights in parks, docks, and summer resorts, 275 lights in railroad depots and shops, 130 lights in mines, smelting works, 380 lights in factories and establishments of various kinds, 1,500 lights in lighting stations, for city lighting, 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

3186-443: The time of their invention, unenclosed lamps were soon discovered to produce large amounts of infrared and harmful ultraviolet-radiation not found in sunlight. If the arc was encased in a glass globe, it was found that many of these invisible rays could be blocked. However, carbon-arcs were soon displaced by safer, more efficient, versatile, and easier to maintain incandescent and gas-discharge lamps. Carbon-arc lamps are still used where

3245-542: The violet and UV portions of the spectrum. Most of the carbon spectra occurs in a very broad line centered at 389 nm (UV-A, just outside the visual spectrum), and a very narrow line at 250 nm (UV-B), plus some other less-powerful lines in the UV-C. Most of the visible and IR radiation is produced from incandescence created at the positive electrode, or anode. Unlike the tungsten anodes found in other arc lamps, which remain relatively cool, carbon produces much higher resistance and

3304-443: The whole length of the tube. An infinite solenoid has infinite length but finite diameter. "Continuous" means that the solenoid is not formed by discrete finite-width coils but by many infinitely thin coils with no space between them; in this abstraction, the solenoid is often viewed as a cylindrical sheet of conductive material. The magnetic field inside an infinitely long solenoid is homogeneous and its strength neither depends on

3363-425: Was contracted to "arc lamp" when the devices came into common usage. In the late nineteenth century, electric arc lighting was in wide use for public lighting. The tendency of electric arcs to flicker and hiss was a major problem. In 1895, Hertha Ayrton wrote a series of articles for The Electrician , explaining that these phenomena were the result of oxygen coming into contact with the carbon rods used to create

3422-410: Was due to the carbon rods used in projector lamphouses having a lifespan of roughly 22 minutes (which corresponds to the amount of film in said reels when projected at 24 frames/second). The projectionist would watch the rod burn down by eye (though a peephole like a welder's glass) and replace the carbon rod when changing film reels. The two-projector changeover setup largely disappeared in the 1970s with

3481-486: Was removed when the two companies merged in 1892 to form the General Electric Company . 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

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