117-485: A fluorescent lamp , or fluorescent tube , is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, to produce ultraviolet and make a phosphor coating in the lamp glow. Fluorescent lamps convert electrical energy into useful light much more efficiently than incandescent lamps , but are less efficient than most LED lamps . The typical luminous efficacy of fluorescent lamps
234-697: A constant-voltage power supply , a fluorescent lamp would rapidly self-destruct because of the uncontrolled current flow. To prevent this, fluorescent lamps must use a ballast to regulate the current flow through the lamp. The terminal voltage across an operating lamp varies depending on the arc current, tube diameter, temperature, and fill gas. A general lighting service 48-inch (1,219 mm) T12 lamp operates at 430 mA, with 100 volts drop. High-output lamps operate at 800 mA, and some types operate up to 1.5 A. The power level varies from 33 to 82 watts per meter of tube length (10 to 25 W/ft) for T12 lamps. The simplest ballast for alternating current (AC) use
351-455: A Geissler tube. He went on to apply thin coatings of luminescent materials to the surfaces of these tubes. Fluorescence occurred, but the tubes were inefficient and had a short operating life. Inquiries that began with the Geissler tube continued as better vacuums were produced. The most famous was the evacuated tube used for scientific research by William Crookes . That tube was evacuated by
468-400: A broader light spectrum than the low pressure sodium lamps. Also used for street lighting, and for artificial photoassimilation for growing plants High pressure mercury-vapor lamps are the oldest high pressure lamp type and have been replaced in most applications by metal halide and the high pressure sodium lamps. They require a shorter arc length. A high-intensity discharge (HID) lamp is
585-418: A capacitor. With no arc current, the transformer and capacitor resonate at line frequency and generate about twice the supply voltage across the tube, and a small electrode heating current. This tube voltage is too low to strike the arc with cold electrodes, but as the electrodes heat up to thermionic emission temperature, the tube striking voltage falls below that of the ringing voltage, and the arc strikes. As
702-429: A cardboard covering was added to protect the aluminium from damage by the strong electrostatic field that produces the cathode rays. Röntgen knew that the cardboard covering prevented light from escaping, yet he observed that the invisible cathode rays caused a fluorescent effect on a small cardboard screen painted with barium platinocyanide when it was placed close to the aluminium window. It occurred to Röntgen that
819-488: A circular tube, used for table lamps or other places where a more compact light source is desired. Larger U-shaped lamps are used to provide the same amount of light in a more compact area, and are used for special architectural purposes. Compact fluorescent lamps have several small-diameter tubes joined in a bundle of two, four, or six, or a small diameter tube coiled in a helix, to provide a high amount of light output in minimal volume. Light-emitting phosphors are applied as
936-482: A consequence of the current, the bulb operated at a higher temperature which necessitated the use of a quartz bulb. Although its light output relative to electrical consumption was better than that of other sources of light, the light it produced was similar to that of the Cooper-Hewitt lamp in that it lacked the red portion of the spectrum, making it unsuitable for ordinary lighting. Due to difficulties in sealing
1053-463: A deformed tube or internal heat-sinks to control cold spot temperature and mercury distribution. Heavily loaded small lamps, such as compact fluorescent lamps, also include heat-sink areas in the tube to maintain mercury vapor pressure at the optimum value. Only a fraction of the electrical energy input into a lamp is converted to useful light. The ballast dissipates some heat; electronic ballasts may be around 90% efficient. A fixed voltage drop occurs at
1170-467: A fluorescent lamp in 1896 that used a coating of calcium tungstate as the fluorescing substance, excited by X-rays . Although it received a patent in 1907, it was not put into production. As with a few other attempts to use Geissler tubes for illumination, it had a short operating life, and given the success of the incandescent light, Edison had little reason to pursue an alternative means of electrical illumination. Nikola Tesla made similar experiments in
1287-530: A fluorescent lamp in 1919 and whose patent application was still pending. GE also had filed a patent application in 1936 in Inman's name to cover the “improvements” wrought by his group. In 1939 GE decided that the claim of Meyer, Spanner, and Germer had some merit, and that in any event a long interference procedure was not in their best interest. They therefore dropped the Buttolph claim and paid $ 180,000 to acquire
SECTION 10
#17328015429911404-452: A heated-cathode lamp, the most common lamp in office lighting and many other applications, produces up to 100 lumens per watt Neon lighting , a widely used form of cold-cathode specialty lighting consisting of long tubes filled with various gases at low pressure excited by high voltages, used as advertising in neon signs . Low pressure sodium lamps , the most efficient gas-discharge lamp type, producing up to 200 lumens per watt, but at
1521-452: A heating current to the cathodes during operation, but the cold cathodes starting increases sputter, and they take much longer to transition from a glow discharge to an arc during warm up, thus the lifespan is typically about half of those seen in comparable rapid-start lamps. Because the formation of an arc requires the thermionic emission of large quantities of electrons from the cathode, rapid start ballast designs provide windings within
1638-502: A high-voltage power supply and a pressure-regulating system for the fill gas. Moore invented an electromagnetically controlled valve that maintained a constant gas pressure within the tube, to extend the working life. Although Moore's lamp was complicated, expensive, and required very high voltages, it was considerably more efficient than incandescent lamps, and it produced a closer approximation to natural daylight than contemporary incandescent lamps. From 1904 onwards Moore's lighting system
1755-517: A lamp for a short time when power is initially applied, and do not repeatedly attempt to restrike a lamp that is dead and unable to sustain an arc; some automatically stop trying to start a failed lamp. This eliminates the re-striking of a lamp and the continuous flashing of a failing lamp with a glow starter. Electronic starters are not subject to wear and do not need replacing periodically, although they may fail like any other electronic circuit. Manufacturers typically quote lives of 20 years, or as long as
1872-595: A lecturer at the University of Strasbourg. In 1875, he became a professor at the Academy of Agriculture at Hohenheim , Württemberg . He returned to Strasbourg as a professor of physics in 1876, and in 1879, he was appointed to the chair of physics at the University of Giessen . In 1888, he obtained the physics chair at the University of Würzburg , and in 1900 at the University of Munich , by special request of
1989-445: A lower loading than their thermionic emission equivalents. Given the higher tube voltage required anyway, these tubes can easily be made long, and even run as series strings. They are better suited for bending into special shapes for lettering and signage, and can also be instantly switched on or off. The gas used in the fluorescent tube must be ionized before the arc can "strike" . For small lamps, it does not take much voltage to strike
2106-507: A metastable state by the impact of an electron, can impart energy to a mercury atom and ionize it, described as the Penning effect . This lowers the breakdown and operating voltage of the lamp, compared to other possible fill gases such as krypton. A fluorescent lamp tube is filled with a mix of argon , xenon , neon , or krypton , and mercury vapor. The pressure inside the lamp is around 0.3% of atmospheric pressure. The partial pressure of
2223-457: A mixture of these gases. Some include additional substances, such as mercury , sodium , and metal halides , which are vaporized during start-up to become part of the gas mixture. Single-ended self-starting lamps are insulated with a mica disc and contained in a borosilicate glass gas discharge tube (arc tube) and a metal cap. They include the sodium-vapor lamp that is the gas-discharge lamp in street lighting. In operation, some of
2340-446: A paint-like coating to the inside of the tube. The organic solvents are allowed to evaporate, then the tube is heated to nearly the melting point of glass to drive off remaining organic compounds and fuse the coating to the lamp tube. Careful control of the grain size of the suspended phosphors is necessary; large grains lead to weak coatings, and small particles lead to poor light maintenance and efficiency. Most phosphors perform best with
2457-511: A particle size around 10 micrometers. The coating must be thick enough to capture all the ultraviolet light produced by the mercury arc, but not so thick that the phosphor coating absorbs too much visible light. The first phosphors were synthetic versions of naturally occurring fluorescent minerals, with small amounts of metals added as activators. Later other compounds were discovered, allowing differing colors of lamps to be made. Fluorescent tubes can have an outer silicone coating applied by dipping
SECTION 20
#17328015429912574-512: A perceivable start-up time to achieve their full light output. Still, owing to their greater efficiency, gas-discharge lamps were preferred over incandescent lights in many lighting applications, until recent improvements in LED lamp technology. The history of gas-discharge lamps began in 1675 when the French astronomer Jean Picard observed that the empty space in his mercury barometer glowed as
2691-530: A reliable electrical discharge, and fluorescent coatings that could be energized by ultraviolet light. At this point, intensive development was more important than basic research. In 1934, Arthur Compton , a renowned physicist and GE consultant, reported to the GE lamp department on successful experiments with fluorescent lighting at General Electric Co., Ltd. in Great Britain (unrelated to General Electric in
2808-452: A result of avalanche ionization , the conductivity of the ionized gas rapidly rises, allowing higher currents to flow through the lamp. The fill gas helps determine the electrical characteristics of the lamp but does not give off light itself. The fill gas effectively increases the distance that electrons travel through the tube, which allows an electron a greater chance of interacting with a mercury atom. Additionally, argon atoms, excited to
2925-621: A single flash of light in the millisecond-microsecond range and is commonly used in film, photography and theatrical lighting. Particularly robust versions of this lamp, known as strobe lights , can produce long sequences of flashes, allowing for the stroboscopic examination of motion . This has found use in the study of mechanical motion, in medicine and in the lighting of dance halls. Wilhelm R%C3%B6ntgen Wilhelm Conrad Röntgen ( / ˈ r ɛ n t ɡ ə n , - dʒ ə n , ˈ r ʌ n t -/ ; German: [ˈvɪlhɛlm ˈʁœntɡən] ; 27 March 1845 – 10 February 1923)
3042-437: A thermal over-current trip to detect repeated starting attempts and disable the circuit until manually reset. A power factor correction (PFC) capacitor draws leading current from the mains to compensate for the lagging current drawn by the lamp circuit. Electronic starters use a different method to preheat the cathodes. They may be plug-in interchangeable with glow starters. They use a semiconductor switch and "soft start"
3159-608: A thin film of a metal such as aluminium. Röntgen published a total of three papers on X-rays between 1895 and 1897. Today, Röntgen is considered the father of diagnostic radiology , the medical speciality which uses imaging to diagnose disease. Röntgen was married to Anna Bertha Ludwig for 47 years until her death in 1919 at the age of 80. In 1866, they met in Zürich at Anna's father's café, Zum Grünen Glas. They became engaged in 1869 and wed in Apeldoorn , Netherlands on 7 July 1872;
3276-563: A type of electrical lamp which produces light by means of an electric arc between tungsten electrodes housed inside a translucent or transparent fused quartz or fused alumina arc tube. Compared to other lamp types, relatively high arc power exists for the arc length. Examples of HID lamps include mercury-vapor lamps , metal halide lamps , ceramic discharge metal halide lamps , sodium vapor lamps and xenon arc lamps HID lamps are typically used when high levels of light and energy efficiency are desired. The Xenon flash lamp produces
3393-550: A whole to benefit from practical applications of the phenomenon. Röntgen was also awarded Barnard Medal for Meritorious Service to Science in 1900. In November 2004, IUPAC named element number 111 roentgenium (Rg) in his honor. IUPAP adopted the name in November 2011. He was elected an International Member of the American Philosophical Society in 1897. In 1907, he became a foreign member of
3510-437: Is 50–100 lumens per watt, several times the efficacy of incandescent bulbs with comparable light output (e.g. the luminous efficacy of an incandescent lamp may only be 16 lm/w). Fluorescent lamp fixtures are more costly than incandescent lamps because, among other things, they require a ballast to regulate current through the lamp, but the initial cost is offset by a much lower running cost. Compact fluorescent lamps made in
3627-515: Is an inductor placed in series, consisting of a winding on a laminated magnetic core. The inductance of this winding limits the flow of AC current. This type of ballast is common in 220–240V countries (And in North America, up to 30W lamps). Ballasts are rated for the size of lamp and power frequency. In North America, the AC voltage is insufficient to start long fluorescent lamps, so the ballast
Fluorescent lamp - Misplaced Pages Continue
3744-455: Is attached to the outside of the lamp glass. This ballast type is incompatible with the European energy saver T8 fluorescent lamps because these lamps require a higher starting voltage than that of the open circuit voltage of rapid start ballasts. Quick-start ballasts use a small auto-transformer to heat the filaments when power is first applied. When an arc strikes, the filament heating power
3861-546: Is critically affected by the temperature of the bulb wall and its effect on the partial pressure of the mercury vapor within. Since mercury condenses at the coolest spot in the lamp, careful design is required to maintain that spot at the optimum temperature, around 40 °C (104 °F). Using an amalgam with some other metal reduces the vapor pressure and increases the optimum temperature range. The bulb wall "cold spot" temperature must still be controlled to prevent condensing. High-output fluorescent lamps have features such as
3978-418: Is not stable. The atom will emit an ultraviolet photon as the atom's electron reverts to a lower, more stable, energy level. Most of the photons that are released from the mercury atoms have wavelengths in the ultraviolet (UV) region of the spectrum, predominantly at wavelengths of 253.7 and 185 nanometers (nm). These are not visible to the human eye, so ultraviolet energy is converted to visible light by
4095-412: Is often a step-up autotransformer with substantial leakage inductance (to limit current flow). Either form of inductive ballast may also include a capacitor for power factor correction. Fluorescent lamps can run directly from a direct current (DC) supply of sufficient voltage to strike an arc. The ballast must be resistive, and would consume about as much power as the lamp. When operated from DC,
4212-524: Is reduced and the tube will start within half a second. The auto-transformer is either combined with the ballast or may be a separate unit. Tubes need to be mounted near an earthed metal reflector in order for them to strike. Quick-start ballasts are more common in commercial installations because of lower maintenance costs. A quick-start ballast eliminates the need for a starter switch, a common source of lamp failures. Nonetheless, Quick-start ballasts are also used in domestic (residential) installations because of
4329-639: The Crookes–Hittorf tube , which had a much thicker glass wall than the Lenard tube, might also cause this fluorescent effect. In the late afternoon of 8 November 1895, Röntgen was determined to test his idea. He carefully constructed a black cardboard covering similar to the one he had used on the Lenard tube. He covered the Crookes–Hittorf tube with the cardboard and attached electrodes to a Ruhmkorff coil to generate an electrostatic charge. Before setting up
4446-700: The Federal Polytechnic Institute in Zürich (today known as the ETH Zurich ), he passed the entrance examination and began his studies there as a student of mechanical engineering . In 1869, he graduated with a PhD from the University of Zurich ; once there, he became a favourite student of Professor August Kundt , whom he followed to the newly founded German Kaiser-Wilhelms-Universität in Strasbourg . In 1874, Röntgen became
4563-500: The Geissler tube , consisting of a partially evacuated glass tube with a metal electrode at either end. When a high voltage was applied between the electrodes, the inside of the tube illuminated with a glow discharge . By putting different chemicals inside, the tubes could be made to produce a variety of colors, and elaborate Geissler tubes were sold for entertainment. More important was its contribution to scientific research. One of
4680-805: The Royal Netherlands Academy of Arts and Sciences . A collection of his papers is held at the National Library of Medicine in Bethesda, Maryland . Today, in Remscheid-Lennep , 40 kilometres east of Röntgen's birthplace in Düsseldorf , is the Deutsches Röntgen-Museum. In Würzburg , where he discovered X-rays, a non-profit organization maintains his laboratory and provides guided tours to
4797-671: The Röntgen Memorial Site . World Radiography Day: World Radiography Day is an annual event promoting the role of medical imaging in modern healthcare. It is celebrated on 8 November each year, coinciding with the anniversary of the Röntgen's discovery. It was first introduced in 2012 as a joint initiative between the European Society of Radiology , the Radiological Society of North America , and
Fluorescent lamp - Misplaced Pages Continue
4914-412: The fluorescence of the inner phosphor coating. The difference in energy between the absorbed ultra-violet photon and the emitted visible light photon heats the phosphor coating. Electric current flows through the tube in a low-pressure arc discharge . Electrons collide with and ionize noble gas atoms inside the bulb surrounding the filament to form a plasma by the process of impact ionization . As
5031-605: The roentgen (R), is also named after him. He was born to Friedrich Conrad Röntgen, a German merchant and cloth manufacturer, and Charlotte Constanze Frowein. When he was aged three, his family moved to the Netherlands, where his mother's family lived. Röntgen attended high school at Utrecht Technical School in Utrecht , Netherlands . He followed courses at the Technical School for almost two years. In 1865, he
5148-403: The 1860s. The lamp consisted of a Geissler tube that was excited by a battery-powered Ruhmkorff induction coil ; an early transformer capable of converting DC currents of low voltage into rapid high-voltage pulses. Initially the lamp generated white light by using a Geissler tube filled with carbon dioxide. However, the carbon dioxide tended to break down. Hence in later lamps, the Geissler tube
5265-534: The 1890s, devising high-frequency powered fluorescent bulbs that gave a bright greenish light, but as with Edison's devices, no commercial success was achieved. One of Edison's former employees created a gas-discharge lamp that achieved a measure of commercial success. In 1895 Daniel McFarlan Moore demonstrated lamps 2 to 3 meters (6.6 to 9.8 ft) in length that used carbon dioxide or nitrogen to emit white or pink light, respectively. They were considerably more complicated than an incandescent bulb, requiring both
5382-784: The Bavarian government. Röntgen had family in Iowa in the United States and planned to emigrate. He accepted an appointment at Columbia University in New York City and bought transatlantic tickets, before the outbreak of World War I changed his plans. He remained in Munich for the rest of his career. During 1895, at his laboratory in the Würzburg Physical Institute of the University of Würzburg, Röntgen
5499-528: The Hull patent gave GE a basis for claiming legal rights over the fluorescent lamp, a few months after the lamp went into production the firm learned of a U.S. patent application that had been filed in 1927 for the aforementioned "metal vapor lamp" invented in Germany by Meyer, Spanner, and Germer. The patent application indicated that the lamp had been created as a superior means of producing ultraviolet light, but
5616-508: The Meyer, et al. application, which at that point was owned by a firm known as Electrons, Inc. The patent was duly awarded in December 1939. This patent, along with the Hull patent, put GE on what seemed to be firm legal ground, although it faced years of legal challenges from Sylvania Electric Products , Inc., which claimed infringement on patents that it held. Even though the patent issue
5733-500: The UV photons that generated them (a phenomenon called Stokes shift ). Incident photons have an energy of 5.5 electron volts but produce visible light photons with energy around 2.5 electron volts, so only 45% of the UV energy is used; the rest is dissipated as heat. Most fluorescent lamps use electrodes that emit electrons into the tube by heat, known as hot cathodes. However, cold cathode tubes have cathodes that emit electrons only due to
5850-413: The United States lamps up to about 30 watts). Before the 1960s, four-pin thermal starters and manual switches were used. A glow switch starter automatically preheats the lamp cathodes. It consists of a normally open bi-metallic switch in a small sealed gas-discharge lamp containing inert gas (neon or argon). The glow switch will cyclically warm the filaments and initiate a pulse voltage to strike
5967-559: The United States). Stimulated by this report, and with all of the key elements available, a team led by George E. Inman built a prototype fluorescent lamp in 1934 at General Electric 's Nela Park (Ohio) engineering laboratory. This was not a trivial exercise; as noted by Arthur A. Bright, "A great deal of experimentation had to be done on lamp sizes and shapes, cathode construction, gas pressures of both argon and mercury vapor, colors of fluorescent powders, methods of attaching them to
SECTION 50
#17328015429916084-411: The application also contained a few statements referring to fluorescent illumination. Efforts to obtain a U.S. patent had met with numerous delays, but were it to be granted, the patent might have caused serious difficulties for GE. At first, GE sought to block the issuance of a patent by claiming that priority should go to one of their employees, Leroy J. Buttolph, who according to their claim had invented
6201-421: The arc and starting the lamp presents no problem, but larger tubes require a substantial voltage (in the range of a thousand volts). Many different starting circuits have been used. The choice of circuit is based on cost, AC voltage, tube length, instant versus non-instant starting, temperature ranges and parts availability. Preheating, also called switchstart, uses a combination filament – cathode at each end of
6318-455: The arc started. Cold cathode lamps have electrodes that operate at room temperature. To start conduction in the lamp a high enough voltage (the striking voltage ) must be applied to ionize the gas, so these lamps require higher voltage to start. Low-pressure lamps have working pressure much less than atmospheric pressure. For example, common fluorescent lamps operate at a pressure of about 0.3% of atmospheric pressure. Fluorescent lamps ,
6435-399: The arc; the process repeats until the lamp is lit. Once the tube strikes, the impinging main discharge keeps the cathodes hot, permitting continued electron emission. The starter switch does not close again because the voltage across the lit tube is insufficient to start a glow discharge in the starter. With glow switch starters a failing tube will cycle repeatedly. Some starter systems used
6552-411: The ballast that continuously warm the cathode filaments. Usually operating at a lower arc voltage than the instant start design; no inductive voltage spike is produced for starting, so the lamps must be mounted near a grounded (earthed) reflector to allow the glow discharge to propagate through the tube and initiate the arc discharge via capacitive coupling . In some lamps a grounded "starting aid" strip
6669-498: The barium platinocyanide screen to test his idea, Röntgen darkened the room to test the opacity of his cardboard cover. As he passed the Ruhmkorff coil charge through the tube, he determined that the cover was light-tight and turned to prepare for the next step of the experiment. It was at this point that Röntgen noticed a faint shimmering from a bench a few feet away from the tube. To be sure, he tried several more discharges and saw
6786-481: The best known gas-discharge lamp. Compared to incandescent lamps , gas-discharge lamps offer higher efficiency , but are more complicated to manufacture and most exhibit negative resistance , causing the resistance in the plasma to decrease as the current flow increases. Therefore, they usually require auxiliary electronic equipment such as ballasts to control current flow through the gas, preventing current runaway ( arc flash ). Some gas-discharge lamps also have
6903-699: The color of the light from the lamp. As a way of evaluating the ability of a light source to reproduce the colors of various objects being lit by the source, the International Commission on Illumination (CIE) introduced the color rendering index (CRI). Some gas-discharge lamps have a relatively low CRI, which means colors they illuminate appear substantially different from how they do under sunlight or other high-CRI illumination. Used in combination with phosphors used to generate many colors of light. Widely used in mercury-vapor lamps and fluorescent tubes . Lamps are divided into families based on
7020-406: The conversion of electrical energy to light is the emission of a photon when an electron in a mercury atom falls from an excited state into a lower energy level . Electrons flowing in the arc collide with the mercury atoms. If the incident electron has enough kinetic energy , it transfers energy to the atom's outer electron, causing that electron to temporarily jump up to a higher energy level that
7137-433: The delay was due to Anna being six years Wilhelm's senior and his father not approving of her age or humble background. Their marriage began with financial difficulties as family support from Röntgen had ceased. They raised one child, Josephine Bertha Ludwig, whom they adopted as a six-year-old after her father, Anna's only brother, died in 1887. For ethical reasons, Röntgen did not seek patents for his discoveries, holding
SECTION 60
#17328015429917254-587: The department of Ardèche , France, and by Dr Camille Benoît, a medical doctor in Privas. In 1864, the French Academy of Sciences awarded Dumas and Benoît a prize of 1,000 francs for their invention. The lamps, cutting-edge technology in their time, gained fame after being described in several of Jules Verne 's science-fiction novels. Each gas, depending on its atomic structure emits radiation of certain wavelengths, its emission spectrum , which determines
7371-411: The desirable feature that a Quick-start ballast light turns on nearly immediately after power is applied (when a switch is turned on). Quick-start ballasts are used only on 240 V circuits and are designed for use with the older, less efficient T12 tubes. The semi-resonant start circuit was invented by Thorn Lighting for use with T12 fluorescent tubes. This method uses a double wound transformer and
7488-511: The discharge becomes an arc. These tubes have no filaments and can be identified by a single pin at each end of the tube (for common lamps; compact cold-cathode lamps may also have a single pin, but operate from a transformer rather than a ballast). The lamp holders have a "disconnect" socket at the low-voltage end which disconnects the ballast when the tube is removed, to prevent electric shock . Instant-start lamps are slightly more energy efficient than rapid start, because they do not constantly send
7605-538: The electrode may still occur, but electrodes can be shaped (e.g. into an internal cylinder) to capture most of the sputtered material so it is not lost from the electrode. Cold cathode lamps are generally less efficient than thermionic emission lamps because the cathode fall voltage is much higher. Power dissipated due to cathode fall voltage does not contribute to light output. However, this is less significant with longer tubes. The increased power dissipation at tube ends also usually means cold cathode tubes have to be run at
7722-456: The electrodes heat, the lamp slowly, over three to five seconds, reaches full brightness. As the arc current increases and tube voltage drops, the circuit provides current limiting. Gas-discharge lamp Gas-discharge lamps are a family of artificial light sources that generate light by sending an electric discharge through an ionized gas, a plasma . Typically, such lamps use a noble gas ( argon , neon , krypton , and xenon ) or
7839-461: The electrodes may be cut in the shape of alphanumeric characters and figural shapes. A flicker light bulb, flicker flame light bulb or flicker glow lamp is a gas-discharge lamp which produces light by ionizing a gas , usually neon mixed with helium and a small amount of nitrogen gas, by an electric current passing through two flame shaped electrode screens coated with partially decomposed barium azide . The ionized gas moves randomly between
7956-404: The electrodes to the quartz, the lamp had a short life. The next step in gas-based lighting took advantage of the luminescent qualities of neon , an inert gas that had been discovered in 1898 by isolation from the atmosphere. Neon glowed a brilliant red when used in Geissler tubes. By 1910, Georges Claude , a Frenchman who had developed a technology and a successful business for air liquefaction,
8073-403: The electrodes, which also produces heat. Some of the energy in the mercury vapor column is also dissipated, but about 85% is turned into visible and ultraviolet light. Not all the UV radiation striking the phosphor coating is converted to visible light; some energy is lost. The largest single loss in modern lamps is due to the lower energy of each photon of visible light, compared to the energy of
8190-435: The electrons are forced to leave the atoms of the gas near the anode by the electric field applied between the two electrodes, leaving these atoms positively ionized . The free electrons thus released flow to the anode, while the cations thus formed are accelerated by the electric field and flow towards the cathode . The ions typically cover only a very short distance before colliding with neutral gas atoms, which give
8307-474: The expense of very poor color rendering . The almost monochromatic yellow light is only acceptable for street lighting and similar applications. A small discharge lamp containing a bi-metallic switch is used to start a fluorescent lamp . In this case the heat of the discharge is used to actuate the switch; the starter is contained in an opaque enclosure and the small light output is not used. Continuous glow lamps are produced for special applications where
8424-413: The first scientists to experiment with a Geissler tube was Julius Plücker , who systematically described in 1858 the luminescent effects that occurred in a Geissler tube. He also made the important observation that the glow in the tube shifted position when in proximity to an electromagnetic field . Alexandre Edmond Becquerel observed in 1859 that certain substances gave off light when they were placed in
8541-493: The fluorescent lamp in their incorporation of a ballast to maintain a constant current. Cooper-Hewitt had not been the first to use mercury vapor for illumination, as earlier efforts had been mounted by Way, Rapieff, Arons, and Bastian and Salisbury. Of particular importance was the mercury-vapor lamp invented by Küch and Retschinsky in Germany . The lamp used a smaller bore bulb and higher current operating at higher pressures. As
8658-537: The highly effective mercury vacuum pump created by Hermann Sprengel . Research conducted by Crookes and others ultimately led to the discovery of the electron in 1897 by J. J. Thomson and X-rays in 1895 by Wilhelm Röntgen . The Crookes tube , as it came to be known, produced little light because the vacuum in it was too great and thus lacked the trace amounts of gas that are needed for electrically stimulated luminescence . Thomas Edison briefly pursued fluorescent lighting for its commercial potential. He invented
8775-455: The idea and Edison used calcium tungstate for his unsuccessful lamp. Other efforts had been mounted, but all were plagued by low efficiency and various technical problems. Of particular importance was the invention in 1927 of a low-voltage “metal vapor lamp” by Friedrich Meyer, Hans-Joachim Spanner, and Edmund Germer , who were employees of a German firm in Berlin . A German patent was granted but
8892-509: The inflation following World War I, Röntgen fell into bankruptcy, spending his final years at his country home at Weilheim , near Munich. Röntgen died on 10 February 1923 from carcinoma of the intestine, also known as colorectal cancer . In keeping with his will, his personal and scientific correspondence, with few exceptions, were destroyed upon his death. He was a member of the Dutch Reformed Church . In 1901, Röntgen
9009-422: The inside of the tube, and other details of the lamp and its auxiliaries before the new device was ready for the public." In addition to having engineers and technicians along with facilities for R&D work on fluorescent lamps, General Electric controlled what it regarded as the key patents covering fluorescent lighting, including the patents originally issued to Hewitt, Moore, and Küch. More important than these
9126-535: The inventive efforts that supported them were of considerable value when the firm took up fluorescent lighting more than two decades later. At about the same time that Moore was developing his lighting system, Peter Cooper Hewitt invented the mercury-vapor lamp , patented in 1901 ( US 682692 ). Hewitt's lamp glowed when an electric current was passed through mercury vapor at a low pressure. Unlike Moore's lamps, Hewitt's were manufactured in standardized sizes and operated at low voltages. The mercury-vapor lamp
9243-405: The ions their electrons. The atoms which lost an electron during the collisions ionize and speed toward the cathode while the ions which gained an electron during the collisions return to a lower energy state , releasing energy in the form of photons . Light of a characteristic frequency is thus emitted. In this way, electrons are relayed through the gas from the cathode to the anode. The color of
9360-399: The lamp by preheating the cathodes before applying a starting pulse which strikes the lamp first time without flickering; this dislodges a minimal amount of material from the cathodes during starting, giving longer lamp life. This is claimed to prolong lamp life by a factor of typically 3 to 4 times for a lamp frequently switched on as in domestic use, and to reduce the blackening of the ends of
9477-482: The lamp in conjunction with a mechanical or automatic ( bi-metallic ) switch (see circuit diagram to the right) that initially connect the filaments in series with the ballast to preheat them; after a short preheating time the starting switch opens. If timed correctly relative to the phase of the supply AC, this causes the ballast to induce a voltage over the tube high enough to initiate the starting arc. These systems are standard equipment in 200–240 V countries (and in
9594-419: The lamp never went into commercial production. All the major features of fluorescent lighting were in place at the end of the 1920s. Decades of invention and development had provided the key components of fluorescent lamps: economically manufactured glass tubing, inert gases for filling the tubes, electrical ballasts, long-lasting electrodes, mercury vapor as a source of luminescence, effective means of producing
9711-450: The lamp typical of fluorescent tubes. While the circuit is complex, the complexity is built into an integrated circuit chip. Electronic starters may be optimized for fast starting (typical start time of 0.3 seconds), or for most reliable starting even at low temperatures and with low supply voltages, with a startup time of 2–4 seconds. The faster-start units may produce audible noise during start-up. Electronic starters only attempt to start
9828-418: The large voltage between the electrodes. The cathodes will be warmed by current flowing through them, but are not hot enough for significant thermionic emission . Because cold cathode lamps have no thermionic emission coating to wear out, they can have much longer lives than hot cathode tubes. This makes them desirable for long-life applications (such as backlights in liquid crystal displays ). Sputtering of
9945-444: The light fitting. Instant start fluorescent tubes were invented in 1944. Instant start simply uses a high enough voltage to break down the gas column and thereby start arc conduction. Once the high-voltage spark "strikes" the arc, the current is boosted until a glow discharge forms. As the lamp warms and pressure increases, the current continues to rise and both resistance and voltage falls, until mains or line-voltage takes over and
10062-401: The light produced depends on the emission spectra of the atoms making up the gas, as well as the pressure of the gas, current density , and other variables. Gas discharge lamps can produce a wide range of colors. Some lamps produce ultraviolet radiation which is converted to visible light by a fluorescent coating on the inside of the lamp's glass surface. The fluorescent lamp is perhaps
10179-435: The mercury jiggled while he was carrying the barometer. Investigators, including Francis Hauksbee , tried to determine the cause of the phenomenon. Hauksbee first demonstrated a gas-discharge lamp in 1705. He showed that an evacuated or partially evacuated glass globe, in which he placed a small amount of mercury, while charged by static electricity could produce a light bright enough to read by. The phenomenon of electric arc
10296-611: The mercury vapor alone is about 0.8 Pa (8 millionths of atmospheric pressure), in a T12 40-watt lamp. The inner surface of the lamp is coated with a fluorescent coating made of varying blends of metallic and rare-earth phosphor salts. The lamp's electrodes are typically made of coiled tungsten and are coated with a mixture of barium, strontium and calcium oxides to improve thermionic emission . Fluorescent lamp tubes are often straight and range in length from about 100 millimeters (3.9 in) for miniature lamps, to 2.43 meters (8.0 ft) for high-output lamps. Some lamps have
10413-569: The metal and the discharge is then produced almost exclusively by the metal vapor. The usual metals are sodium and mercury owing to their visible spectrum emission. One hundred years of research later led to lamps without electrodes which are instead energized by microwave or radio-frequency sources. In addition, light sources of much lower output have been created, extending the applications of discharge lighting to home or indoor use. Ruhmkorff lamps were an early form of portable electric lamp, named after Heinrich Daniel Ruhmkorff and first used in
10530-456: The nature of electricity and light phenomena as developed by the British scientists Michael Faraday in the 1840s and James Clerk Maxwell in the 1860s. Little more was done with this phenomenon until 1856 when German glassblower Heinrich Geissler created a mercury vacuum pump that evacuated a glass tube to an extent not previously possible. Geissler invented the first gas-discharge lamp,
10647-460: The neon light also was significant for the last key element of the fluorescent lamp, its fluorescent coating. In 1926 Jacques Risler received a French patent for the application of fluorescent coatings to neon light tubes. The main use of these lamps, which can be considered the first commercially successful fluorescents, was for advertising, not general illumination. This, however, was not the first use of fluorescent coatings; Becquerel had earlier used
10764-403: The new rays he temporarily termed "X-rays", using the mathematical designation ("X") for something unknown. The new rays came to bear his name in many languages as "Röntgen rays" (and the associated X-ray radiograms as "Röntgenograms"). At one point, while he was investigating the ability of various materials to stop the rays, Röntgen brought a small piece of lead into position while a discharge
10881-428: The pressure of gas, and whether or not the cathode is heated. Hot cathode lamps have electrodes that operate at a high temperature and are heated by the arc current in the lamp. The heat knocks electrons out of the electrodes by thermionic emission , which helps maintain the arc. In many types the electrodes consist of electrical filaments made of fine wire, which are heated by a separate current at startup, to get
10998-470: The same shimmering each time. Striking a match, he discovered the shimmering had come from the location of the barium platinocyanide screen he had been intending to use next. Based on the formation of regular shadows, Röntgen termed the phenomenon "rays". As 8 November was a Friday, he took advantage of the weekend to repeat his experiments and made his first notes. In the following weeks, he ate and slept in his laboratory as he investigated many properties of
11115-579: The same sizes as incandescent lamp bulbs are used as an energy-saving alternative to incandescent lamps in homes. In the United States , fluorescent lamps are classified as universal waste . The United States Environmental Protection Agency recommends that fluorescent lamps be segregated from general waste for recycling or safe disposal, and some jurisdictions require recycling of them. The fluorescence of certain rocks and other substances had been observed for hundreds of years before its nature
11232-474: The starting switch is often arranged to reverse the polarity of the supply to the lamp each time it is started; otherwise, the mercury accumulates at one end of the tube. Fluorescent lamps are (almost) never operated directly from DC for those reasons. Instead, an inverter converts the DC into AC and provides the current-limiting function as described below for electronic ballasts. The performance of fluorescent lamps
11349-459: The tube into a solution of water and silicone, and then drying the tube. This coating gives the tube a silky surface finish, and protects against moisture, guaranteeing a predictable surface resistance on the tube when starting it. Fluorescent lamps are negative differential resistance devices, so as more current flows through them, the electrical resistance of the fluorescent lamp drops, allowing for even more current to flow. Connected directly to
11466-720: The two electrodes which produces a flickering effect, often marketed as suggestive of a candle flame (see image). High-pressure lamps have a discharge that takes place in gas under slightly less to greater than atmospheric pressure. For example, a high pressure sodium lamp has an arc tube under 100 to 200 torr pressure, about 14% to 28% of atmospheric pressure; some automotive HID headlamps have up to 50 bar or fifty times atmospheric pressure. Metal halide lamps produce almost white light, and attain 100 lumen per watt light output. Applications include indoor lighting of high buildings, parking lots, shops, sport terrains. High pressure sodium lamps , producing up to 150 lumens per watt produce
11583-410: The view that they should be publicly available without charge. After receiving his Nobel prize money, Röntgen donated the 50,000 Swedish krona to research at the University of Würzburg . Although he accepted the honorary degree of Doctor of Medicine, he rejected an offer of lower nobility, or Niederer Adelstitel, denying the preposition von (meaning "of") as a nobiliary particle (i.e., von Röntgen). With
11700-628: Was a German physicist , who, on 8 November 1895 , produced and detected electromagnetic radiation in a wavelength range known as X-rays or Röntgen rays, an achievement that earned him the inaugural Nobel Prize in Physics in 1901 . In honour of Röntgen's accomplishments, in 2004, the International Union of Pure and Applied Chemistry (IUPAC) named element 111, roentgenium , a radioactive element with multiple unstable isotopes, after him. The non- SI unit of radiation exposure ,
11817-567: Was a patent covering an electrode that did not disintegrate at the gas pressures that ultimately were employed in fluorescent lamps. Albert W. Hull of GE's Schenectady Research Laboratory filed for a patent on this invention in 1927, which was issued in 1931. General Electric used its control of the patents to prevent competition with its incandescent lights and probably delayed the introduction of fluorescent lighting by 20 years. Eventually, war production required 24-hour factories with economical lighting, and fluorescent lights became available. While
11934-528: Was awarded the first Nobel Prize in Physics . The award was officially "in recognition of the extraordinary services he has rendered by the discovery of the remarkable rays subsequently named after him". Shy in public speaking, he declined to give a Nobel lecture. Röntgen donated the 50,000 Swedish krona reward from his Nobel Prize to research at his university, the University of Würzburg . Like Marie and Pierre Curie , Röntgen refused to take out patents related to his discovery of X-rays, as he wanted society as
12051-692: Was by Westinghouse and General Electric and Showcase/Display Case fixtures were introduced by Artcraft Fluorescent Lighting Corporation in 1946. During the following year, GE and Westinghouse publicized the new lights through exhibitions at the New York World's Fair and the Golden Gate International Exposition in San Francisco. Fluorescent lighting systems spread rapidly during World War II as wartime manufacturing intensified lighting demand. By 1951 more light
12168-452: Was filled with nitrogen (which generated red light), and the clear glass was replaced with uranium glass (which fluoresced with a green light). Intended for use in the potentially explosive environment of mining, as well as oxygen-free environments like diving or for a heatless lamp for possible use in surgery, the lamp was actually developed both by Alphonse Dumas, an engineer at the iron mines of Saint-Priest and of Lac, near Privas , in
12285-659: Was first described by Vasily V. Petrov in 1802. In 1809, Sir Humphry Davy demonstrated the electric arc at the Royal Institution of Great Britain. Since then, discharge light sources have been researched because they create light from electricity considerably more efficiently than incandescent light bulbs . The father of the low-pressure gas discharge tube was German glassblower Heinrich Geissler , who beginning in 1857 constructed colorful artistic cold cathode tubes with different gases in them which glowed with many different colors, called Geissler tubes . It
12402-432: Was found that inert gases such as the noble gases neon, argon, krypton or xenon, as well as carbon dioxide worked well in tubes. This technology was commercialized by the French engineer Georges Claude in 1910 and became neon lighting , used in neon signs . The introduction of the metal vapor lamp, including various metals within the discharge tube, was a later advance. The heat of the gas discharge vaporizes some of
12519-429: Was installed in a number of stores and offices. Its success contributed to General Electric 's motivation to improve the incandescent lamp, especially its filament. GE's efforts came to fruition with the invention of a tungsten -based filament. The extended lifespan and improved efficacy of incandescent bulbs negated one of the key advantages of Moore's lamp, but GE purchased the relevant patents in 1912. These patents and
12636-411: Was investigating the external effects of passing an electrical discharge through various types of vacuum tube equipment—apparatuses from Heinrich Hertz , Johann Hittorf , William Crookes , Nikola Tesla and Philipp von Lenard In early November, he was repeating an experiment with one of Lenard's tubes in which a thin aluminium window had been added to permit the cathode rays to exit the tube but
12753-504: Was not completely resolved for many years, General Electric's strength in manufacturing and marketing gave it a pre-eminent position in the emerging fluorescent light market. Sales of "fluorescent lumiline lamps" commenced in 1938 when four different sizes of tubes were put on the market. They were used in fixtures manufactured by three leading corporations: Lightolier , Artcraft Fluorescent Lighting Corporation , and Globe Lighting. The Slimline fluorescent ballast's public introduction in 1946
12870-460: Was obtaining enough neon as a byproduct to support a neon lighting industry. While neon lighting was used around 1930 in France for general illumination, it was no more energy-efficient than conventional incandescent lighting. Neon tube lighting, which also includes the use of argon and mercury vapor as alternative gases, came to be used primarily for eye-catching signs and advertisements. Neon lighting
12987-503: Was occurring. Röntgen thus saw the first radiographic image: his own flickering ghostly skeleton on the barium platinocyanide screen. About six weeks after his discovery, he took a picture—a radiograph —using X-rays of his wife Anna Bertha's hand. When she saw her skeleton she exclaimed "I have seen my death!" He later took a better picture of his friend Albert von Kölliker 's hand at a public lecture. Röntgen's original paper, "On A New Kind of Rays" ( Ueber eine neue Art von Strahlen ),
13104-421: Was produced in the United States by fluorescent lamps than by incandescent lamps. In the first years zinc orthosilicate with varying content of beryllium was used as greenish phosphor. Small additions of magnesium tungstate improved the blue portion of the spectrum, yielding acceptable white. After the discovery that beryllium was toxic , halophosphate-based phosphors dominated. The fundamental mechanism for
13221-564: Was published on 28 December 1895. On 5 January 1896, an Austrian newspaper reported Röntgen's discovery of a new type of radiation. Röntgen was awarded an honorary Doctor of Medicine degree from the University of Würzburg after his discovery. He also received the Rumford Medal of the British Royal Society in 1896, jointly with Philipp Lenard , who had already shown that a portion of the cathode rays could pass through
13338-444: Was relevant to the development of fluorescent lighting, however, as Claude's improved electrode (patented in 1915) overcame "sputtering", a major source of electrode degradation. Sputtering occurred when ionized particles struck an electrode and tore off bits of metal. Although Claude's invention required electrodes with a lot of surface area, it showed that a major impediment to gas-based lighting could be overcome. The development of
13455-596: Was superior to the incandescent lamps of the time in terms of energy efficiency , but the blue-green light it produced limited its applications. It was, however, used for photography and some industrial processes. Mercury vapor lamps continued to be developed at a slow pace, especially in Europe. By the early 1930s they received limited use for large-scale illumination. Some of them employed fluorescent coatings, but these were used primarily for color correction and not for enhanced light output. Mercury vapor lamps also anticipated
13572-441: Was understood. One of the first to explain it was Irish scientist Sir George Stokes from the University of Cambridge in 1852, who named the phenomenon "fluorescence" after fluorite , a mineral many of whose samples glow strongly because of impurities. By mid-19th century, experimenters had observed a radiant glow emanating from partially evacuated glass vessels through which an electric current passed. The explanation relied on
13689-405: Was unfairly expelled from high school when one of his teachers intercepted a caricature of one of the teachers, which was drawn by someone else. Without a high school diploma, Röntgen could only attend university in the Netherlands as a visitor. In 1865, he tried to attend Utrecht University without having the necessary credentials required for a regular student. Upon hearing that he could enter
#990009