1.
Ion source
–
An ion source is a device that creates atomic and molecular ions. Ion sources are used to form ions for mass spectrometers, optical emission spectrometers, particle accelerators, ion implanters, Electron ionization is widely used in mass spectrometry, particularly for organic molecules. The electrons may be created by an arc discharge between a cathode and an anode, an electron beam ion source is used in atomic physics to produce highly charged ions by bombarding atoms with a powerful electron beam. Its principle of operation is shared by the electron beam ion trap, Electron capture ionization is the ionization of a gas phase atom or molecule by attachment of an electron to create an ion of the form A−•. The reaction is A + e − → M A − where the M over the arrow denotes that to conserve energy, Electron capture can be used in conjunction with chemical ionization. An electron capture detector is used in gas chromatography systems. Chemical ionization is a lower energy process than electron ionization because it involves ion/molecule reactions rather than electron removal, the lower energy yields less fragmentation, and usually a simpler spectrum. A typical CI spectrum has an easily identifiable molecular ion, in a CI experiment, ions are produced through the collision of the analyte with ions of a reagent gas in the ion source. Some common reagent gases include, methane, ammonia, and isobutane, inside the ion source, the reagent gas is present in large excess compared to the analyte. Electrons entering the source will preferentially ionize the reagent gas, the resultant collisions with other reagent gas molecules will create an ionization plasma. Positive and negative ions of the analyte are formed by reactions with this plasma. For example, protonation occurs by CH4 + e − ⟶ CH4 + +2 e −, charge-exchange ionization is a gas phase reaction between an ion and an atom or molecule in which the charge of the ion is transferred to the neutral species. A + + B ⟶ A + B + Chemi-ionization is the formation of an ion through the reaction of a gas atom or molecule with an atom or molecule in an excited state. Associative ionization is a gas phase reaction in which two atoms or molecules interact to form a single product ion, one or both of the interacting species may have excess internal energy. For example, A ∗ + B ⟶ AB + ∙ + e − where species A with excess internal energy interacts with B to form the ion AB+, Penning ionization is a form of chemi-ionization involving reactions between neutral atoms or molecules. The process is named after the Dutch physicist Frans Michel Penning who first reported it in 1927, Penning ionization involves a reaction between a gas-phase excited-state atom or molecule G* and a target molecule M resulting in the formation of a radical molecular cation M+. In a radioactive ion source, a piece of radioactive material. This is used in smoke detectors and ion mobility spectrometers
Ion source
–
Mass spectrometer EI/CI ion source
Ion source
–
Electron ionization source schematic
Ion source
–
NASA's
NEXT (ion thruster) space craft propulsion system
Ion source
–
Electrospray ion source
2.
Cathode
–
A cathode is the electrode from which a conventional current leaves a polarized electrical device. A conventional current describes the direction in which positive electronic charges move, Electrons have a negative charge, so the movement of electrons is opposite to the conventional current flow. Consequently, the mnemonic cathode current departs also means that flow into the devices cathode. Cathode polarity with respect to the anode can be positive or negative and this outward current is carried internally by positive ions moving from the electrolyte to the positive cathode. It is continued externally by electrons moving inwards, this negative charge moving inwards constituting positive current flowing outwards, for example, the Daniell galvanic cells copper electrode is the positive terminal and the cathode. In a recharging battery, or an electrolytic cell performing electrolysis, for example, reversing the current direction in a Daniell galvanic cell would produce an electrolytic cell, where the copper electrode is the positive terminal and the anode. In a diode, the cathode is the terminal at the pointed end of the arrow symbol. Note, electrode naming for diodes is always based on the direction of the forward current, an electrode through which current flows the other way is termed an anode. The use of West to mean the out direction may appear unnecessarily contrived, previously, as related in the first reference cited above, Faraday had used the more straightforward term exode. The reference he used to effect was the Earths magnetic field direction. The flow of electrons is almost always from anode to cathode outside of the cell or device, regardless of the cell or device type, an exception is when a diode reverse-conducts, either by accident or by design. In chemistry, a cathode is the electrode of a cell at which reduction occurs. Another mnemonic is to note the cathode has a c, as does reduction, perhaps most useful would be to remember cathode corresponds to cation and anode corresponds to anion. The cathode can be negative like when the cell is electrolytic, the cathode supplies electrons to the positively charged cations which flow to it from the electrolyte. The cathodic current, in electrochemistry, is the flow of electrons from the interface to a species in solution. The anodic current is the flow of electrons into the anode from a species in solution, in an electrolytic cell, the cathode is where the negative polarity is applied to drive the cell. Common results of reduction at the cathode are hydrogen gas or pure metal from metal ions, when discussing the relative reducing power of two redox agents, the couple for generating the more reducing species is said to be more cathodic with respect to the more easily reduced reagent. When metal ions are reduced from ionic solution, they form a metal surface on the cathode
Cathode
–
Glow from the directly heated cathode of a 1 kW power
tetrode tube in a radio transmitter. The cathode filament is not directly visible
Cathode
–
Diagram of a
copper cathode in a
galvanic cell (e.g., a battery). A positive current i flows out of the cathode.
Cathode
–
Two indirectly-heated cathodes (orange heater strip) in ECC83 dual triode tube
Cathode
–
Cold cathode (lefthand electrode) in
neon lamp
3.
Electrical filament
–
An incandescent light bulb, incandescent lamp or incandescent light globe is an electric light with a wire filament heated to such a high temperature that it glows with visible light. The filament, heated by passing a current through it, is protected from oxidation with a glass or quartz bulb that is filled with inert gas or evacuated. In a halogen lamp, filament evaporation is prevented by a process that redeposits metal vapor onto the filament. The light bulb is supplied with current by feed-through terminals or wires embedded in the glass. Most bulbs are used in a socket which provides mechanical support, Incandescent bulbs are manufactured in a wide range of sizes, light output, and voltage ratings, from 1.5 volts to about 300 volts. They require no external regulating equipment, have low manufacturing costs, the remaining energy is converted into heat. The luminous efficacy of an incandescent bulb is 16 lumens per watt. Some applications of the incandescent bulb deliberately use the heat generated by the filament, such applications include incubators, brooding boxes for poultry, heat lights for reptile tanks, infrared heating for industrial heating and drying processes, lava lamps, and the Easy-Bake Oven toy. In addressing the question of who invented the incandescent lamp, historians Robert Friedel and Paul Israel list 22 inventors of incandescent lamps prior to Joseph Swan, historian Thomas Hughes has attributed Edisons success to his development of an entire, integrated system of electric lighting. In 1761 Ebenezer Kinnersley demonstrated heating a wire to incandescence and it was not bright enough nor did it last long enough to be practical, but it was the precedent behind the efforts of scores of experimenters over the next 75 years. Over the first three-quarters of the 19th century many experimenters worked with various combinations of platinum or iridium wires, carbon rods, many of these devices were demonstrated and some were patented. In 1835, James Bowman Lindsay demonstrated a constant electric light at a meeting in Dundee. He stated that he could read a book at a distance of one, however, having perfected the device to his own satisfaction, he turned to the problem of wireless telegraphy and did not develop the electric light any further. His claims are not well documented, although he is credited in Challoner et al. with being the inventor of the Incandescent Light Bulb, in 1838, Belgian lithographer Marcellin Jobard invented an incandescent light bulb with a vacuum atmosphere using a carbon filament. In 1840, British scientist Warren de la Rue enclosed a coiled platinum filament in a vacuum tube, although a workable design, the cost of the platinum made it impractical for commercial use. In 1841, Frederick de Moleyns of England was granted the first patent for an incandescent lamp, in 1845, American John W. Starr acquired a patent for his incandescent light bulb involving the use of carbon filaments. He died shortly after obtaining the patent, and his invention was never produced commercially, little else is known about him. In 1851, Jean Eugène Robert-Houdin publicly demonstrated incandescent light bulbs on his estate in Blois and his light bulbs are on display in the museum of the Château de Blois
Electrical filament
–
Original carbon-filament bulb from
Thomas Edison 's shop in Menlo Park
Electrical filament
–
A 230-volt incandescent light bulb, with a 'medium' sized
E27 (Edison 27 mm) male screw base. The filament is visible as the horizontal line between the vertical supply wires.
Electrical filament
–
Carbon filament lamps, showing darkening of bulb
Electrical filament
–
Sir Joseph Wilson Swan
4.
Thermionic emission
–
Thermionic emission is the thermally induced flow of charge carriers from a surface or over a potential-energy barrier. This occurs because the energy given to the carrier overcomes the work function of the material. The charge carriers can be electrons or ions, and in literature are sometimes referred to as thermions. After emission, a charge that is equal in magnitude and opposite in sign to the total charge emitted is initially left behind in the emitting region, the classical example of thermionic emission is the emission of electrons from a hot cathode into a vacuum in a vacuum tube. The hot cathode can be a metal filament, a metal filament. Vacuum emission from metals tends to become significant only for temperatures over 1,000 K, the term thermionic emission is now also used to refer to any thermally-excited charge emission process, even when the charge is emitted from one solid-state region into another. This process is important in the operation of a variety of electronic devices. The magnitude of the flow increases dramatically with increasing temperature. The phenomenon was reported in 1853 by Edmond Becquerel. It was rediscovered in 1873 by Frederick Guthrie in Britain, while doing work on charged objects, Guthrie discovered that a red-hot iron sphere with a negative charge would lose its charge. He also found that this did not happen if the sphere had a positive charge, other early contributors included Johann Wilhelm Hittorf, Eugen Goldstein, and Julius Elster and Hans Friedrich Geitel. Edison built several experimental lamp bulbs with a wire, metal plate, or foil inside the bulb that was separate from the filament. He connected a galvanometer, a used to measure current. If the foil was put at a negative potential relative to the filament and we now know that the filament was emitting electrons, which were attracted to a positively charged foil, but not a negatively charged one. This one-way current was called the Edison effect and he found that the current emitted by the hot filament increased rapidly with increasing voltage, and filed a patent application for a voltage-regulating device using the effect on November 15,1883. He found that sufficient current would pass through the device to operate a telegraph sounder and this was exhibited at the International Electrical Exposition in Philadelphia in September 1884. William Preece, a British scientist, took back with him several of the Edison effect bulbs and he presented a paper on them in 1885, where he referred to thermionic emission as the Edison Effect. The British physicist John Ambrose Fleming, working for the British Wireless Telegraphy Company, Fleming went on to develop the two-element vacuum tube known as the diode, which he patented on November 16,1904
Thermionic emission
–
Closeup of the
filament on a low pressure mercury
gas discharge lamp showing white thermionic emission mix coating on the central portion of the coil. Typically made of a mixture of
barium,
strontium and
calcium oxides, the coating is
sputtered away through normal use, often eventually resulting in lamp failure.
Thermionic emission
–
One of the bulbs with which Edison discovered thermionic emission. It consists of an evacuated glass light bulb containing a carbon filament (hairpin shape), with an additional metal plate attached to wires emerging from the base. Electrons released by the filament were attracted to the plate when it had a positive voltage.
5.
Gas discharge lamp
–
Gas-discharge lamps are a family of artificial light sources that generate light by sending an electrical discharge through an ionized gas, a plasma. Typically, such use a noble gas or a mixture of these gases. Some include additional substances, like mercury, sodium, and metal halides, in operation some of the atoms in the gas are positively ionized, losing one of their electrons. These free electrons move toward the positive electrode, the ions are accelerated by the electric field toward whichever electrode is negatively charged at the time. Typically, after traveling a short distance, the ions collide with neutral gas atoms. In this way, electrons are relayed through the gas from the electrode to the positive. The color of the light produced depends on the spectra of the atoms making up the gas, as well as the pressure of the gas, current density. Gas discharge lamps can produce a range of colors. Some lamps produce ultraviolet radiation which is converted to light by a fluorescent coating on the inside of the lamps glass surface. The fluorescent lamp is perhaps the best known gas-discharge lamp, therefore, they usually require auxiliary electronic equipment such as ballasts to control current flow through the gas, preventing current runaway. Some gas-discharge lamps also have a perceivable start-up time to achieve their full light output, still, due to their greater efficiency, gas-discharge lamps are replacing incandescent lights in many lighting applications. 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, since then, discharge light sources have been researched because they create light from electricity considerably more efficiently than incandescent light bulbs. It was found that inert gases like the noble gases neon, argon, krypton or xenon and this technology was commercialized by 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 tube, was a later advance. The heat of the gas discharge vaporized some of the metal, the usual metals are sodium and mercury owing to their visible spectrum emission. One hundred years of research led to lamps without electrodes which are instead energized by microwave or radio frequency sources. In addition, light sources of lower output have been created
Gas discharge lamp
–
Germicidal lamps are simple low-pressure mercury vapor discharges in a fused quartz envelope.
Gas discharge lamp
–
Helium
Gas discharge lamp
Gas discharge lamp
–
Neon
6.
Neon lamp
–
A neon lamp is a miniature gas discharge lamp. The lamp typically consists of a glass capsule that contains a mixture of neon and other gases at a low pressure. When sufficient voltage is applied and sufficient current is supplied between the electrodes, the lamp produces an orange glow discharge, Neon glow lamps are widely used as indicator lamps in the displays of electronic instruments and appliances. Neon was discovered in 1898 by William Ramsay and Morris W. Travers, neons scarcity precluded its prompt application for electrical lighting along the lines of Moore tubes, which used electric discharges in nitrogen. Moore tubes were commercialized by their inventor, Daniel McFarlan Moore, around 1917, Daniel Moore developed the neon lamp while working at the General Electric Company. The lamp has a different design from the much larger neon tubes used for neon lighting. The difference in design was sufficient that a U. S. patent was issued for the lamp in 1919, a Smithsonian Institution website notes, These small, low power devices use a physical principle called coronal discharge. Moore mounted two electrodes close together in a bulb and added neon or argon gas, the electrodes would glow brightly in red or blue, depending on the gas, and the lamps lasted for years. Since the electrodes could take almost any shape imaginable, an application has been fanciful decorative lamps. Glow lamps found practical use as indicators in instrument panels and in home appliances until the widespread commercialisation of Light-Emitting Diodes in the 1970s. A small electric current, which may be AC or DC, is allowed through the tube, the gas is typically a Penning mixture,99. 5% neon and 0. 5% argon, which has lower striking voltage than pure neon, at a pressure of 1-20 torr. The lamp glow discharge lights at its striking voltage, the voltage required to sustain the discharge is significantly lower than the striking voltage. This is due to the organization of positive ions near the cathode, Neon lamps operate using a low current glow discharge. Higher power devices, such as lamps or metal halide lamps use a higher current arc discharge. Low pressure sodium-vapor lamps use a neon Penning mixture for warm up, once the neon lamp has reached breakdown, it can support a large current flow. Because of this characteristic, electrical circuitry external to the lamp must limit the current through the circuit or else the current will rapidly increase until the lamp is destroyed. For indicator-sized lamps, a resistor typically limits the current, in contrast, larger sized lamps often use a specially constructed high voltage transformer with high leakage inductance or other electrical ballast to limit the available current. When the current through the lamp is lower than the current for the highest-current discharge path and this may be a sign of aging of the indicator bulb, and is exploited in the decorative flicker flame neon lamps
Neon lamp
–
NE-2 type neon lamp powered by
alternating current
Neon lamp
–
A
General Electric NE-34 glow lamp, manufactured circa 1930
Neon lamp
–
Switch on a power strip, illuminated by a neon lamp
Neon lamp
–
DC (left and center) and AC (right) supplied NE-2 type neon lamps
7.
Discharge tube
–
A gas-filled tube, also known as a discharge tube, is an arrangement of electrodes in a gas within an insulating, temperature-resistant envelope. A gas-discharge lamp is a light using a gas-filled tube. Specialized gas-filled tubes such as krytrons, thyratrons, and ignitrons are used as switching devices in electronics, the voltage required to initiate and sustain discharge is dependent on the pressure and composition of the fill gas and geometry of the tube. Although the envelope is typically glass, power tubes often use ceramics, both hot cathode and cold cathode type devices are encountered. Hydrogen is used in tubes used for very fast switching, e. g. some thyratrons, dekatrons, and krytrons, the build-up and recovery times of hydrogen are much shorter than in other gases. Deuterium is used in lamps for ultraviolet spectroscopy, in neutron generator tubes. It has higher voltage than hydrogen. In fast switching tubes it is used instead of hydrogen where high voltage operation is required, for a comparison, the hydrogen-filled CX1140 thyratron has anode voltage rating of 25 kV, while the deuterium-filled and otherwise identical CX1159 has 33 kV. Also, at the voltage the pressure of deuterium can be higher than of hydrogen. Significantly higher peak powers are achievable and its recovery time is however about 40% slower than for hydrogen. Noble gases are used in tubes for many purposes, from lighting to switching. Pure noble gases are employed in switching tubes, noble-gas-filled thyratrons have better electrical parameters than mercury-based ones. The electrodes undergo damage by high-velocity ions, the neutral atoms of the gas slow the ions down by collisions, and reduce the energy transferred to the electrodes by the ion impact. Gases with high weight, e. g. xenon, protect the electrodes better than lighter ones. Helium is used in lasers and in some thyratrons rated for high currents. Helium provides about as short time as hydrogen, but can withstand lower voltage. Neon has low voltage and is frequently used in low-voltage tubes. Discharge in neon emits relatively bright red light, neon-filled switching tubes therefore also act as indicators and this is exploited in the decatron tubes, which act as both counters and displays
Discharge tube
–
A
compact fluorescent bulb is a household application of a gas-filled tube
Discharge tube
–
Noble gas discharge tubes; from left to right:
helium,
neon,
argon,
krypton,
xenon
Discharge tube
–
Other gases in discharge tubes; from left to right:
hydrogen,
deuterium,
nitrogen,
oxygen,
mercury
8.
Vacuum tube
–
In electronics, a vacuum tube, an electron tube, or just a tube, or valve, is a device that controls electric current between electrodes in an evacuated container. Vacuum tubes mostly rely on thermionic emission of electrons from a hot filament or a cathode heated by the filament and this type is called a thermionic tube or thermionic valve. A phototube, however, achieves electron emission through the photoelectric effect, the simplest vacuum tube, the diode, contains only a heater, a heated electron-emitting cathode, and a plate. Current can only flow in one direction through the device between the two electrodes, as electrons emitted by the travel through the tube and are collected by the anode. Adding one or more control grids within the tube allows the current between the cathode and anode to be controlled by the voltage on the grid or grids, Tubes with grids can be used for many purposes, including amplification, rectification, switching, oscillation, and display. In the 1940s the invention of devices made it possible to produce solid-state devices, which are smaller, more efficient, more reliable, more durable. Hence, from the mid-1950s solid-state devices such as transistors gradually replaced tubes, the cathode-ray tube remained the basis for televisions and video monitors until superseded in the 21st century. However, there are still a few applications for which tubes are preferred to semiconductors, for example, the used in microwave ovens. One classification of vacuum tubes is by the number of active electrodes, a device with two active elements is a diode, usually used for rectification. Devices with three elements are used for amplification and switching. Additional electrodes create tetrodes, pentodes, and so forth, which have additional functions made possible by the additional controllable electrodes. X-ray tubes are vacuum tubes. Phototubes and photomultipliers rely on electron flow through a vacuum, though in those cases electron emission from the cathode depends on energy from photons rather than thermionic emission, since these sorts of vacuum tubes have functions other than electronic amplification and rectification they are described in their own articles. A vacuum tube consists of two or more electrodes in a vacuum inside an airtight enclosure, most tubes have glass envelopes, though ceramic and metal envelopes have been used. The electrodes are attached to leads which pass through the envelope via an airtight seal, Tubes were a frequent cause of failure in electronic equipment, and consumers were expected to be able to replace tubes themselves. In addition to the terminals, some tubes had an electrode terminating at a top cap. The principal reason for doing this was to avoid leakage resistance through the tube base, the bases were commonly made with phenolic insulation which performs poorly as an insulator in humid conditions. There was even a design that had two top cap connections
Vacuum tube
–
Modern vacuum tubes, mostly miniature style
Vacuum tube
–
One of Edison's experimental bulbs
Vacuum tube
–
Fleming's first diodes
Vacuum tube
–
The first triode, the De Forest
Audion, invented in 1906
9.
Hot cathode
–
In vacuum tubes, a hot cathode or thermionic cathode is a cathode electrode which is heated to make it emit electrons due to thermionic emission. This is in contrast to a cold cathode which does not have a heating element, the heating element is usually an electrical filament, heated by a separate electric current passing through it. Hot cathodes typically achieve higher power density than cold cathodes. Cold cathodes rely on electron emission or secondary electron emission from positive ion bombardment. There are two types of hot cathode, in a directly heated cathode, the filament is the cathode and emits the electrons. In an indirectly heated cathode, the filament or heater heats a separate cathode electrode which emits the electrons. From the 1920s to the 1960s, virtually every electronic device used hot vacuum tubes. Today, hot cathodes are used as the source of electrons in fluorescent lamps, vacuum tubes, a cathode electrode in a vacuum tube or other vacuum system is a metal surface which emits electrons into the evacuated space of the tube. Since the negatively charged electrons are attracted to the nuclei of the metal atoms, they normally stay inside the metal. This energy is called the function of the metal. In a hot cathode, the surface is induced to emit electrons by heating it with a filament. The cathode heats to a temperature that causes electrons to be boiled out of its surface into the space in the tube. There are two types of hot cathodes, Directly heated cathode In this type, the filament itself is the cathode, Directly heated cathodes were used in the first vacuum tubes. Today they are used in fluorescent tubes and most high power transmitting vacuum tubes, indirectly heated cathodes are used in most low power vacuum tubes. For example, in most vacuum tubes the cathode is a tube heated by a tungsten filament inside it. The filament of a heated cathode is usually called the heater. In a tube in which the filament itself was the cathode and it also allows the filaments in all the tubes in an electronic device to be tied together and supplied from the same current source, even though the cathodes they heat may be at different potentials. In order to improve electron emission, cathodes are treated with chemicals
Hot cathode
–
A tungsten filament in a low pressure mercury gas discharge lamp which emits electrons. To increase electron emission a white thermionic emission mix coating is applied, visible on the central portion of the coil. Typically made of a mixture of
barium,
strontium and
calcium oxides, the coating is sputtered away through normal use, often eventually resulting in lamp failure.
Hot cathode
–
Two indirectly-heated cathodes (orange heater strip) in
ECC83 dual triode tube
Hot cathode
–
Glow of a directly-heated cathode in an Eimac 4-1000A 1 kW power
triode tube in a
radio transmitter. Directly heated cathodes operate at higher temperatures and produce a brighter glow. The cathode is behind the other tube elements and not directly visible.
Hot cathode
–
Lanthanum hexaboride hot cathode
10.
Nixie tube
–
A Nixie tube, or cold cathode display, is an electronic device for displaying numerals or other information using glow discharge. The glass tube contains a wire-mesh anode and multiple cathodes, shaped like numerals or other symbols, applying power to one cathode surrounds it with an orange glow discharge. The tube is filled with a gas at low pressure, usually mostly neon and often a little mercury or argon, although it resembles a vacuum tube in appearance, its operation does not depend on thermionic emission of electrons from a heated cathode. It is therefore called a tube, or a variant of neon lamp. Such tubes rarely exceed 40 °C even under the most severe of operating conditions in a room at ambient temperature, the early Nixie displays were made by a small vacuum tube manufacturer called Haydu Brothers Laboratories, and introduced in 1955 by Burroughs Corporation, who purchased Haydu. The name Nixie was derived by Burroughs from NIX I, an abbreviation of Numeric Indicator eXperimental No,1, although this may have been a backronym designed to evoke a mythical creature. Hundreds of variations of design were manufactured by many firms. The Burroughs Corporation introduced Nixie and owned the name Nixie as a trademark, nixie-like displays made by other firms had trademarked names including Digitron, Inditron and Numicator. A proper generic term is cold cathode neon readout tube, though the phrase Nixie tube quickly entered the vernacular as a generic name, Burroughs even had another Haydu tube that could operate as a digital counter and directly drive a Nixie tube for display. This was called a Trochotron, in later form known as the Beam-X Switch counter tube, another name was magnetron beam-switching tube, trochotrons were used in the UNIVAC1101 computer, as well as in clocks and frequency counters. The first trochotrons were surrounded by a cylindrical magnet, with poles at the ends. The field inside the magnet had essentially-parallel lines of force, parallel to the axis of the tube and it was a thermionic vacuum tube, inside were a central cathode, ten anodes, and ten spade electrodes. The magnetic field and voltages applied to the made the electrons form a thick sheet that went to only one anode. Applying a pulse with specified width and voltages to the made the sheet advance to the next anode. A later form of trochotron called a Beam-X Switch replaced the large, glow-transfer counting tubes, similar in essential function to the trochotrons, had a glow discharge on one of a number of main cathodes, visible through the top of the glass envelope. Sets of guide cathodes between the indicating cathodes moved the glow in steps to the main cathode. Types with two or three sets of guide cathodes could count in either direction, a well-known trade name for glow-transfer counter tubes in the United Kingdom was Dekatron. Types with connections to each individual indicating cathode, which enabled presetting the tubes state to any value, were trade named Selectron tubes, however, their construction was cruder, their average lifetime was shorter, and they failed to find many applications due to their complex periphery
Nixie tube
–
Inside the nixie tube
Nixie tube
–
The ten digits of a GN-4 Nixie tube.
Nixie tube
–
Systron-Donner frequency counter from 1973 with Nixie-tube display
Nixie tube
–
This ИН-19А Nixie tube displays symbols, including % and °C
11.
Geissler tube
–
A Geissler tube is an early gas discharge tube used to demonstrate the principles of electrical glow discharge, similar to modern neon lighting. The tube was invented by the German physicist and glassblower Heinrich Geissler in 1857, when a high voltage is applied between the electrodes, an electrical current flows through the tube. The current dissociates electrons from the gas molecules, creating ions, and when the electrons recombine with the ions, the color of light emitted is characteristic of the material within the tube, and many different colors and lighting effects can be achieved. The first gas-discharge lamps, Geissler tubes were novelty items, made in many artistic shapes, in the early 20th century, the technology was commercialized and evolved into neon lighting. Geissler tubes were mass-produced from the 1880s as novelty and entertainment devices, with various spherical chambers, some tubes were very elaborate and complex in shape and would contain chambers within an outer casing. A novel effect could be obtained by spinning a tube at high speed with a motor. When an operating tube was touched by the hand the shape of the glowing discharge inside often changed, simple straight Geissler tubes were used in turn-of-the-century scientific research as high voltage indicators. When a Geissler tube was brought near a source of high voltage alternating current such as a Tesla coil or Ruhmkorff coil and they were used to tune the tank circuits of radio transmitters to resonance. Another example of their use was to find nodes of standing waves on transmission lines, another use c1900 was as the light source in Pulfrich refractometers. Geissler tubes are still used in physics education to demonstrate the principles of gas discharge tubes. Geissler tubes were the first gas discharge tubes, and have had a impact on the development of many instruments. One of the most significant consequences of Geissler tube technology was the discovery of the electron, by the 1870s better vacuum pumps enabled scientists to evacuate Geissler tubes to a higher vacuum, these were called Crookes tubes after William Crookes. When current was applied, it was found that the envelope of these tubes would glow at the end opposite to the cathode. In 1897 J. J. Thomson showed that cathode rays consisted of an unknown particle
Geissler tube
–
Drawing of Geissler tubes from 1869 French physics book, showing some of the many decorative shapes and colors.
Geissler tube
–
Modern recreation of a Geissler tube in a museum
12.
Cathode ray tube
–
The cathode ray tube is a vacuum tube that contains one or more electron guns and a phosphorescent screen, and is used to display images. It modulates, accelerates, and deflects electron beam onto the screen to create the images, the images may represent electrical waveforms, pictures, radar targets, or others. CRTs have also used as memory devices, in which case the visible light emitted from the fluorescent material is not intended to have significant meaning to a visual observer. In television sets and computer monitors, the front area of the tube is scanned repetitively and systematically in a fixed pattern called a raster. An image is produced by controlling the intensity of each of the three beams, one for each additive primary color with a video signal as a reference. A CRT is constructed from an envelope which is large, deep, fairly heavy. The interior of a CRT is evacuated to approximately 0.01 Pa to 133 nPa. evacuation being necessary to facilitate the flight of electrons from the gun to the tubes face. That it is evacuated makes handling an intact CRT potentially dangerous due to the risk of breaking the tube and causing a violent implosion that can hurl shards of glass at great velocity. As a matter of safety, the face is made of thick lead glass so as to be highly shatter-resistant and to block most X-ray emissions. Flat panel displays can also be made in large sizes, whereas 38 to 40 was about the largest size of a CRT television, flat panels are available in 60. Cathode rays were discovered by Johann Hittorf in 1869 in primitive Crookes tubes and he observed that some unknown rays were emitted from the cathode which could cast shadows on the glowing wall of the tube, indicating the rays were traveling in straight lines. In 1890, Arthur Schuster demonstrated cathode rays could be deflected by electric fields, the earliest version of the CRT was known as the Braun tube, invented by the German physicist Ferdinand Braun in 1897. It was a diode, a modification of the Crookes tube with a phosphor-coated screen. In 1907, Russian scientist Boris Rosing used a CRT in the end of an experimental video signal to form a picture. He managed to display simple geometric shapes onto the screen, which marked the first time that CRT technology was used for what is now known as television. The first cathode ray tube to use a hot cathode was developed by John B. Johnson and Harry Weiner Weinhart of Western Electric and it was named by inventor Vladimir K. Zworykin in 1929. RCA was granted a trademark for the term in 1932, it released the term to the public domain in 1950. The first commercially made electronic television sets with cathode ray tubes were manufactured by Telefunken in Germany in 1934, in oscilloscope CRTs, electrostatic deflection is used, rather than the magnetic deflection commonly used with television and other large CRTs
Cathode ray tube
–
A 14 inch cathode ray tube showing its deflection coils and electron guns
Cathode ray tube
–
Cutaway rendering of a color CRT: 1. Three electron guns (for red, green, and blue phosphor dots) 2. Electron beams 3. Focusing coils 4. Deflection coils 5. Anode connection 6. Mask for separating beams for red, green, and blue part of displayed image 7. Phosphor layer with red, green, and blue zones 8. Close-up of the phosphor-coated inner side of the screen
Cathode ray tube
–
Typical 1950s United States television set
Cathode ray tube
–
A flat CRT assembly inside a 1984 Sinclair FTV1 pocket TV
13.
Negative resistance
–
This is in contrast to an ordinary resistor in which an increase of applied voltage causes a proportional increase in current due to Ohms law, resulting in a positive resistance. While a positive resistance consumes power from current passing through it, under certain conditions it can increase the power of an electrical signal, amplifying it. Negative resistance is a property which occurs in a few nonlinear electronic components. The term negative resistance refers to negative resistance, Δ v / Δ i <0. They are used in oscillators and amplifiers, particularly at microwave frequencies. Most microwave energy is produced with negative resistance devices. They can also have hysteresis and be bistable, and so are used in switching, examples of devices with negative differential resistance are tunnel diodes, Gunn diodes, and gas discharge tubes such as neon lamps. In addition, circuits containing amplifying devices such as transistors and op amps with positive feedback can have negative differential resistance and these are used in oscillators and active filters. Because they are nonlinear, negative resistance devices have a complicated behavior than the positive ohmic resistances usually encountered in electric circuits. Therefore, there is no real negative resistor analogous to a positive resistor, the resistance between two terminals of an electrical device or circuit is determined by its current–voltage curve, giving the current i through it for any given voltage v across it. Most materials, including the ordinary resistances encountered in electrical circuits, obey Ohms law, so the I–V curve of an ohmic resistance is a straight line through the origin with positive slope. The resistance is the ratio of voltage to current, the slope of the line and is constant. Negative resistance occurs in a few nonlinear devices, in a nonlinear component the I–V curve is not a straight line, so it does not obey Ohms law. Resistance can still be defined, but the resistance is not constant and it is the inverse slope of the line from the origin through the point on the I–V curve. Thus power sources formally have negative static resistance, however this term is never used in practice, because the term resistance is only applied to passive components. Static resistance determines the power dissipation in a component, passive devices, which consume electric power, have positive static resistance, while active devices, which produce electric power, do not. Differential resistance is only relevant to time-varying currents, points on the curve where the slope is negative, meaning an increase in voltage causes a decrease in current, have negative differential resistance. Devices of this type can amplify signals, and are what is meant by the term negative resistance
Negative resistance
Negative resistance
–
A
Gunn diode, a
semiconductor device with negative differential resistance used in
electronic oscillators to generate
microwaves
Negative resistance
–
An
oscillator consisting of a
Gunn diode inside a
cavity resonator. The negative resistance of the diode excites
microwave oscillations in the cavity, which radiate through the aperture into a
waveguide (not shown).
Negative resistance
–
8–12 GHz microwave amplifier consisting of two cascaded tunnel diode reflection amplifiers
14.
Bell Laboratories
–
Nokia Bell Labs is an American research and scientific development company, owned by Finnish company Nokia. Its headquarters are located in Murray Hill, New Jersey, in addition to laboratories around the rest of the United States. The historic laboratory originated in the late 19th century as the Volta Laboratory, Bell Labs was also at one time a division of the American Telephone & Telegraph Company, half-owned through its Western Electric manufacturing subsidiary. Eight Nobel Prizes have been awarded for work completed at Bell Laboratories, in 1880, the French government awarded Alexander Graham Bell the Volta Prize of 50,000 francs, approximately US$10,000 at that time for the invention of the telephone. Bell used the award to fund the Volta Laboratory in Washington, D. C. in collaboration with Sumner Tainter, the laboratory is also variously known as the Volta Bureau, the Bell Carriage House, the Bell Laboratory and the Volta Laboratory. The laboratory focused on the analysis, recording, and transmission of sound, Bell used his considerable profits from the laboratory for further research and education to permit the diffusion of knowledge relating to the deaf. This resulted in the founding of the Volta Bureau c,1887, located at Bells fathers house at 1527 35th Street in Washington, D. C. where its carriage house became their headquarters in 1889. In 1893, Bell constructed a new building, close by at 1537 35th St. specifically to house the lab, the building was declared a National Historic Landmark in 1972. In 1884, the American Bell Telephone Company created the Mechanical Department from the Electrical, the first president of research was Frank B. Jewett, who stayed there until 1940, ownership of Bell Laboratories was evenly split between AT&T and the Western Electric Company. Its principal work was to plan, design, and support the equipment that Western Electric built for Bell System operating companies and this included everything from telephones, telephone exchange switches, and transmission equipment. Bell Labs also carried out consulting work for the Bell Telephone Company, a few workers were assigned to basic research, and this attracted much attention, especially since they produced several Nobel Prize winners. Until the 1940s, the principal locations were in and around the Bell Labs Building in New York City. Of these, Murray Hill and Crawford Hill remain in existence, the largest grouping of people in the company was in Illinois, at Naperville-Lisle, in the Chicago area, which had the largest concentration of employees prior to 2001. Since 2001, many of the locations have been scaled down or closed. The Holmdel site, a 1.9 million square foot structure set on 473 acres, was closed in 2007, the mirrored-glass building was designed by Eero Saarinen. In August 2013, Somerset Development bought the building, intending to redevelop it into a commercial and residential project. The prospects of success are clouded by the difficulty of readapting Saarinens design and by the current glut of aging, eight Nobel Prizes have been awarded for work completed at Bell Laboratories
Bell Laboratories
–
Logotype of Bell Labs in 2014.
Bell Laboratories
–
Bell's 1893 Volta Bureau building in Washington, D.C.
Bell Laboratories
–
Reconstruction of the directional antenna used in the discovery of radio emission of extraterrestrial origin by
Karl Guthe Jansky at
Bell Telephone Laboratories in 1932.
Bell Laboratories
–
The first
transistor, a
point-contact germanium device, was invented at Bell Laboratories in 1947. This image shows a replica.
15.
Thyratron
–
A thyratron is a type of gas-filled tube used as a high-power electrical switch and controlled rectifier. Thyratrons can handle much greater currents than similar hard-vacuum tubes, electron multiplication occurs when the gas becomes ionized, producing a phenomenon known as Townsend discharge. Gases used include mercury vapor, xenon, neon, and hydrogen, unlike a vacuum tube, a thyratron cannot be used to amplify signals linearly. Gas rectifiers, which predated vacuum tubes, such as the argon-filled General Electric Tungar bulb, irving Langmuir and G. S. Meikle of GE are usually cited as the first investigators to study controlled rectification in gas tubes, about 1914. The first commercial thyratrons didnt appear until around 1928, a solid-state device with similar operating characteristics is the thyristor, also known as the silicon controlled rectifier. The term thyristor was derived from a combination of thyratron and transistor, since the 1960s thyristors have replaced thyratrons in most low- and medium-power applications. A typical hot-cathode thyratron uses a heated filament cathode, completely contained within an assembly with a control grid on one open side. In the off situation the voltage on the grid is negative with respect to the cathode. When positive voltage is applied to the anode, no current flows, the electrons will ionize the gas by collisions with the gas in the tube, and an avalanche effect results, causing an arc discharge between cathode and anode. The shield prevents ionized current paths that form within other parts of the tube. The gas in a thyratron is typically at a fraction of the pressure of air at sea level,15 to 30 millibars is typical. For a cold-cathode thyratron the trigger voltage on the grid will typically be positive. Both hot- and cold-cathode versions are encountered, a hot cathode is at an advantage, as ionization of the gas is made easier, thus, the tubes control electrode is more sensitive. Once turned on, the thyratron will remain on as long as there is a significant current flowing through it, when the anode voltage or current falls to zero, the device switches off. Glow thyratrons were optimized for high light output or even phosphorized and used as self-displaying shift registers in large-format. Another use of the thyratron was in relaxation oscillators, since the plate turn-on voltage is much higher than the turn-off voltage the tube has hysteresis and with a capacitor across it could function as a sawtooth oscillator. The voltage on the grid controlled the breakdown voltage and thus the period of oscillation, Thyratron relaxation oscillators were used in power inverters and oscilloscope sweep circuits. One miniature thyratron, the triode 6D4, found a use as a potent noise source
Thyratron
–
Giant
GE hydrogen thyratron, used in pulsed
radars, next to miniature 2D21 thyratron used to trigger
relays in
jukeboxes
Thyratron
–
Rare Z806W relay tube used in elevators
Thyratron
–
Wynn-Williams' Scale-of-Two Counter using thyratrons. (With permission of the
Cavendish Laboratory,
University of Cambridge, UK.)
Thyratron
–
R.C.A. brand 885 Triode Thyratron
16.
Krytron
–
The krytron is a cold-cathode gas-filled tube intended for use as a very high-speed switch, somewhat similar to the thyratron. It consists of a glass tube with four electrodes. A small triggering pulse on the grid electrode switches the tube on, the vacuum version is called a vacuum krytron, or sprytron. The krytron was one of the earliest developments of the EG&G Corporation, the krytron is a development of the triggered spark gaps and thyratrons originally developed for radar transmitters during World War II. The gas used in krytrons is hydrogen, noble gases can also be used, two are a conventional anode and cathode. One is an electrode, arranged to be close to the cathode. The keep-alive has a low positive voltage applied, which causes an area of gas to ionize near the cathode. High voltage is applied to the anode, but primary conduction does not occur until a positive pulse is applied to the trigger electrode, once started, arc conduction carries a considerable current. The fourth is a grid, usually wrapped around the anode. In place of or in addition to the keep-alive electrode some krytrons may contain a tiny amount of radioactive material. The radiation source serves to increase the reliability of ignition and formation of the keep-alive electrode discharge, the gas filling provides ions for neutralizing the space charge and allowing high currents at lower voltage. The electric arc is self-sustaining, once the tube is triggered, krytrons and sprytrons are triggered by a high voltage from a capacitor discharge via a trigger transformer, in a similar way flashtubes for e. g. photoflash applications are triggered. Devices integrating a krytron with a transformer are available. A sprytron, also known as vacuum krytron or triggered vacuum switch, is a vacuum, rather than gas-filled and it is designed for use in environments with high levels of ionizing radiation, which might trigger a gas-filled krytron spuriously. It is also immune to electromagnetic interference than gas filled tubes. Sprytrons lack the keepalive electrode and the radioactive source. The trigger pulse must be stronger than for a krytron, sprytrons are able to handle higher currents, krytrons tend to be used for triggering a secondary switch, e. g. a triggered spark gap, while sprytrons are usually connected directly to the load. The trigger pulse has to be more intense, as there is no preionized gas path for the electric current
Krytron
–
KN2 "Krytron" switch tube, made by
EG&G (about 25 mm tall)
Krytron
–
For the microwave/radio amplifying tube, see
Klystron. For the cryoelectric switch, see
Cryotron.
17.
Voltage regulator
–
A voltage regulator is designed to automatically maintain a constant voltage level. A voltage regulator may be a simple feed-forward design or may include negative feedback control loops and it may use an electromechanical mechanism, or electronic components. Depending on the design, it may be used to one or more AC or DC voltages. Electronic voltage regulators are found in such as computer power supplies where they stabilize the DC voltages used by the processor. In automobile alternators and central power station generator plants, voltage regulators control the output of the plant, a simple voltage/current regulator can be made from a resistor in series with a diode. Due to the shape of diode V-I curves, the voltage across the diode changes only slightly due to changes in current drawn or changes in the input. When precise voltage control and efficiency are not important, this design may be fine, feedback voltage regulators operate by comparing the actual output voltage to some fixed reference voltage. Any difference is amplified and used to control the element in such a way as to reduce the voltage error. This forms a feedback control loop, increasing the open-loop gain tends to increase regulation accuracy. There will also be a trade-off between stability and the speed of the response to changes, in electromechanical regulators, voltage regulation is easily accomplished by coiling the sensing wire to make an electromagnet. The magnetic field produced by the current attracts a moving ferrous core held back under spring tension or gravitational pull, as voltage increases, so does the current, strengthening the magnetic field produced by the coil and pulling the core towards the field. The magnet is connected to a mechanical power switch, which opens as the magnet moves into the field. As voltage decreases, so does the current, releasing spring tension or the weight of the core and this closes the switch and allows the power to flow once more. The rectifier diodes in an alternator automatically perform this function so that a relay is not required. More modern designs now use solid state technology to perform the function that the relays perform in electromechanical regulators. Electromechanical regulators are used for mains voltage stabilisation — see AC voltage stabilizers below, to control the output of generators automatic voltage regulators are used. While the basic principle is the same, the system itself is more complex, an automatic voltage regulator consists of several components such as diodes, capacitors, resistors and potentiometers or even microcontrollers, all placed on a circuit board. This is then mounted near the generator and connected with wires to measure
Voltage regulator
–
An
integrated circuit voltage regulator in a
TO-220 style package. Such devices are popular because they require few or no external components and provide the functions of pass element, voltage reference, and protection from overcurrent in one package.
Voltage regulator
–
A voltage stabilizer using electromechanical relays for switching.
Voltage regulator
–
Voltage regulator for generators.
Voltage regulator
–
Magnetic mains regulator
18.
Glow discharge
–
A glow discharge is a plasma formed by the passage of electric current through a low-pressure gas. It is created by applying a voltage between two electrodes in a glass tube containing gas. When the voltage exceeds a value called the striking voltage, the gas in the tube ionizes, becoming a plasma. The color depends on the gas used, glow discharge is widely used as a source of light in devices such as neon lights, fluorescent lamps, and plasma-screen televisions. Analyzing the light produced by spectroscopy can reveal much about the interactions in the gas, so glow discharge is used in plasma physics. It is also used in the surface treatment technique called sputtering, the simplest type of glow discharge is a direct-current glow discharge. In its simplest form, it consists of two electrodes in a cell held at low pressure, the cell is typically filled with neon, but other gases can also be used. An electric potential of several hundred volts is applied between the two electrodes, a small fraction of the population of atoms within the cell is initially ionized through random processes. The ions are driven towards the cathode by the potential. The initial population of ions and electrons collides with other atoms, as long as the potential is maintained, a population of ions and electrons remains. Some of the kinetic energy is transferred to the cathode. This happens partially through the ions striking the cathode directly, the primary mechanism, however, is less direct. Ions strike the more numerous neutral gas atoms, transferring a portion of their energy to them and these neutral atoms then strike the cathode. Whichever species strike the cathode, collisions within the cathode redistribute this energy until a portion of the cathode is ejected and this process is known as sputtering. Once free of the cathode, atoms move into the bulk of the discharge through drift. The atoms can then be excited by collisions with ions, electrons, once excited, atoms will lose their energy fairly quickly. Of the various ways that this energy can be lost, the most important is radiatively, in atomic mass spectrometry, these ions are detected. Their mass identifies the type of atoms and their quantity reveals the amount of element in the sample
Glow discharge
–
NE-2 type neon lamp powered by
alternating current
Glow discharge
–
DC powered neon lamp, showing glow discharge surrounding only the cathode
Glow discharge
–
A 5651 voltage-regulator tube in operation
19.
Dekatron
–
In electronics, a Dekatron is a gas-filled decade counting tube. Dekatrons were used in computers, calculators and other counting-related products during the 1950s and 1960s, Dekatron, now a generic trademark, was the brand name used by the British Ericsson Telephones Limited, of Beeston, Nottingham. Dekatrons usually have an input frequency in the high kilohertz range –100 kHz is fast,1 MHz is around the maximum possible. These frequencies are obtained in hydrogen-filled fast dekatrons, Dekatrons filled with inert gas are inherently more stable and have a longer life, but their counting frequency is limited to 10 kHz. Internal designs vary by the model and manufacturer, but generally a dekatron has ten cathodes, the cathodes are arranged in a circle with a guide electrode between each cathode. When the guide electrode is pulsed properly, the gas will activate near the guide pins then jump to the next cathode. Pulsing the guide electrodes repeatedly will cause the dot to move from cathode to cathode. Hydrogen dekatrons require high voltages ranging from 400 to 600 volts on the anode for proper operation, dekatrons with inert gas usually require ~350 volts. When a dekatron is first powered up, a dot appears at a random cathode. The color of the dot depends on the type of gas that is in the tube, neon-filled tubes display a red-orange dot, argon-filled tubes display a purple dot. Counter/Selector dekatrons have each cathode wired to its own pin, therefore their bases have at least 13 pins, selectors allow for monitoring the status of each cathode or to divide-by-n with the proper reset circuitry. This kind of versatility made such dekatrons useful for numerical division in early calculators, Dekatrons come in various physical sizes, ranging from smaller than a 7-pin miniature vacuum tube to as large as an octal base tube. While most dekatrons are decimal counters, models were made to count in base-5. The dekatron fell out of use when transistor-based counters became reliable and affordable. Today, dekatrons are used by hobbyists in simple spinners that run off the mains frequency or as a numeric indicator for homemade clocks. Sumlock ANITA calculator — The worlds first desktop electronic calculators, which used Dekatrons, WITCH — Early British relay-based computer that used Dekatrons. Ericsson Telephones computing tubes designation system Special Quality gas-filled tubes designation system Jennings, Thomas ‘Tom’, Nixie Indicators and Decimal Counting Tubes, vacuum Tubes, Cold-Cathode Switching Tubes & Dekatron Counter Tubes, Calculator Electronics, Vintage Calculators Web Museum. Spinner for European mains, Electric stuff, UK, spinner for American mains, Electronix & more, archived from the original on 2007-06-07
Dekatron
–
An octal-base dekatron.
Dekatron
–
A dekatron in operation.
Dekatron
–
Detail of the top of a dekatron — central anode disk surrounded by 30 internal cathode pins.
20.
Integrated circuit
–
An integrated circuit or monolithic integrated circuit is a set of electronic circuits on one small flat piece of semiconductor material, normally silicon. The ICs mass production capability, reliability and building-block approach to circuit design ensured the rapid adoption of standardized ICs in place of using discrete transistors. ICs are now used in all electronic equipment and have revolutionized the world of electronics. Computers, mobile phones, and other home appliances are now inextricable parts of the structure of modern societies, made possible by the small size. These advances, roughly following Moores law, allow a computer chip of 2016 to have millions of times the capacity, ICs have two main advantages over discrete circuits, cost and performance. Cost is low because the chips, with all their components, are printed as a unit by photolithography rather than being constructed one transistor at a time, furthermore, packaged ICs use much less material than discrete circuits. Performance is high because the ICs components switch quickly and consume little power because of their small size, the main disadvantage of ICs is the high cost to design them and fabricate the required photomasks. This high initial cost means ICs are only practical when high production volumes are anticipated, Circuits meeting this definition can be constructed using many different technologies, including thin-film transistor, thick film technology, or hybrid integrated circuit. However, in general usage integrated circuit has come to refer to the single-piece circuit construction originally known as a integrated circuit. Jacobi disclosed small and cheap hearing aids as typical industrial applications of his patent, an immediate commercial use of his patent has not been reported. The idea of the circuit was conceived by Geoffrey Dummer. Dummer presented the idea to the public at the Symposium on Progress in Quality Electronic Components in Washington and he gave many symposia publicly to propagate his ideas, and unsuccessfully attempted to build such a circuit in 1956. A precursor idea to the IC was to create small ceramic squares, Components could then be integrated and wired into a bidimensional or tridimensional compact grid. This idea, which seemed very promising in 1957, was proposed to the US Army by Jack Kilby, however, as the project was gaining momentum, Kilby came up with a new, revolutionary design, the IC. In his patent application of 6 February 1959, Kilby described his new device as a body of semiconductor material … wherein all the components of the circuit are completely integrated. The first customer for the new invention was the US Air Force, Kilby won the 2000 Nobel Prize in Physics for his part in the invention of the integrated circuit. His work was named an IEEE Milestone in 2009, half a year after Kilby, Robert Noyce at Fairchild Semiconductor developed his own idea of an integrated circuit that solved many practical problems Kilbys had not. Noyces design was made of silicon, whereas Kilbys chip was made of germanium, Noyce credited Kurt Lehovec of Sprague Electric for the principle of p–n junction isolation, a key concept behind the IC
Integrated circuit
–
Erasable programmable read-only memory integrated circuits. These
packages have a transparent window that shows the
die inside. The window allows the memory to be erased by exposing the chip to
ultraviolet light.
Integrated circuit
–
Integrated circuit from an
EPROM memory microchip showing the memory blocks, the supporting circuitry and the fine silver wires which connect the integrated circuit die to the legs of the packaging.
Integrated circuit
–
Jack Kilby 's original integrated circuit
Integrated circuit
–
The
die from an Intel
8742, an 8-bit
microcontroller that includes a
CPU running at 12 MHz, 128 bytes of
RAM, 2048 bytes of
EPROM, and
I/O in the same chip
21.
Flash tube
–
A flashtube, also called a flashlamp, is an electric arc lamp designed to produce extremely intense, incoherent, full-spectrum white light for very short durations. Flashtubes are made of a length of tubing with electrodes at either end and are filled with a gas that. Flashtubes are used mostly for photographic purposes but are employed in scientific, medical, industrial. The lamp comprises a hermetically sealed tube, which is filled with a noble gas, usually xenon. Additionally, a high power source is necessary to energize the gas as a trigger event. A charged capacitor is used to supply energy for the flash. In some applications, the emission of light is undesired, whether due to production of ozone, damage to laser rods, degradation of plastics. In these cases, a fused silica is used. A better alternative is a cerium-doped quartz, it does not suffer from solarization and has higher efficiency and its cutoff is at about 380 nm. The power level of the lamps is rated in watts/area, total electrical input power divided by the inner wall surface. Cooling of the electrodes and the envelope is of high importance at high power levels. Air cooling is sufficient for lower power levels. High power lamps are cooled with a liquid, typically by flowing demineralized water through a tube in which the lamp is encased, water-cooled lamps will generally have the glass shrunk around the electrodes, to provide a direct thermal conductor between them and the cooling water. The cooling medium should flow also across the length of the lamp. Above 15 W/cm2 forced air cooling is required, liquid cooling if in a confined space, liquid cooling is generally necessary above 30 W/cm2. For this reason, thinner glass is used for continuous-wave arc-lamps. Thicker materials can generally handle more impact energy from the wave that a short-pulsed arc can generate. The material of the envelope provides another limit for the power,1 mm thick fused quartz has a limit of 200 W/cm2
Flash tube
–
Helical xenon flashtube - Animated version below
Flash tube
–
Flashtubes of various sizes for laser pumping. The top three are xenon flashtubes. The last one is a krypton arc lamp, (shown for comparison).
Flash tube
–
Xenon flashtubes used on
smartphones and cameras are usually externally triggered.
Flash tube
–
A ruby laser head, assembled and disassembled, revealing pumping cavity, the ruby rod, and two water-cooled flashtubes.
22.
Xenon
–
Xenon is a chemical element with symbol Xe and atomic number 54. It is a colorless, dense, odorless gas found in the Earths atmosphere in trace amounts. Although generally unreactive, xenon can undergo a few chemical reactions such as the formation of xenon hexafluoroplatinate, Xenon is used in flash lamps and arc lamps, and as a general anesthetic. The first excimer laser used a xenon dimer molecule as the lasing medium. Xenon is used to search for hypothetical weakly interacting massive particles, naturally occurring xenon consists of eight stable isotopes. More than 40 unstable xenon isotopes undergo radioactive decay, and the ratios of xenon are an important tool for studying the early history of the Solar System. Radioactive xenon-135 is produced by beta decay from iodine-135, and is the most significant neutron absorber in nuclear reactors, Xenon was discovered in England by the Scottish chemist William Ramsay and English chemist Morris Travers in September 1898, shortly after their discovery of the elements krypton and neon. They found xenon in the left over from evaporating components of liquid air. Ramsay suggested the name xenon for this gas from the Greek word ξένον, neuter singular form of ξένος, meaning foreign, strange, in 1902, Ramsay estimated the proportion of xenon in the Earths atmosphere to be one part in 20 million. During the 1930s, American engineer Harold Edgerton began exploring strobe light technology for high speed photography and this led him to the invention of the xenon flash lamp in which light is generated by passing brief electric current through a tube filled with xenon gas. In 1934, Edgerton was able to generate flashes as brief as one microsecond with this method, in 1939, American physician Albert R. Behnke Jr. began exploring the causes of drunkenness in deep-sea divers. He tested the effects of varying the breathing mixtures on his subjects, from his results, he deduced that xenon gas could serve as an anesthetic. Xenon was first used as an anesthetic in 1951 by American anesthesiologist Stuart C. Cullen, who used it with two patients. Xenon and the noble gases were for a long time considered to be completely chemically inert. Since O2 and xenon have almost the same first ionization potential, on March 23,1962, he mixed the two gases and produced the first known compound of a noble gas, xenon hexafluoroplatinate. Bartlett thought its composition to be Xe+−, but later revealed that it was probably a mixture of various xenon-containing salts. By 1971, more than 80 xenon compounds were known, in November 1989, IBM scientists demonstrated a technology capable of manipulating individual atoms
Xenon
–
A xenon-filled
discharge tube glowing light blue
Xenon
–
Spectral lines of xenon
Xenon
–
Xenon flash (
animated version)
Xenon
–
XeF 4 crystals, 1962
23.
Stroboscope
–
A stroboscope also known as a strobe, is an instrument used to make a cyclically moving object appear to be slow-moving, or stationary. It consists of either a disk with slots or holes or a lamp such as a flashtube which produces brief repetitive flashes of light. Usually the rate of the stroboscope is adjustable to different frequencies, when a rotating or vibrating object is observed with the stroboscope at its vibration frequency, it appears stationary. Thus stroboscopes are used to measure frequency. The principle is used for the study of rotating, reciprocating, oscillating or vibrating objects, machine parts and vibrating strings are common examples. A stroboscope used to set the timing of internal combustion engines is called a timing light. In its simplest mechanical form, a cylinder with evenly spaced holes or slots placed in the line of sight between the observer and the moving object. The observer looks through the holes/slots on the near and far side at the same time, when the holes/slots are aligned on opposite sides, the object is visible to the observer. Alternately, a single moving hole or slot can be used with a hole or slot. The stationary hole or slot limits the light to a single viewing path, viewing through a single line of holes/slots does not work, since the holes/slots appear to just sweep across the object without a strobe effect. The rotational speed is adjusted so that it becomes synchronised with the movement of the observed system, the illusion is caused by temporal aliasing, commonly known as the stroboscopic effect. In electronic versions, the disc is replaced by a lamp capable of emitting brief. Typically a gas-discharge or solid-state lamp is used, because they are capable of emitting light nearly instantly when power is applied, by comparison, incandescent lamps have a brief warm-up when energized, followed by a cool-down period when power is removed. These delays result in smearing and blurring of detail of objects partially illuminated during the warm-up, for most applications, incandescent lamps are too slow for clear stroboscopic effects. Yet when operated from an AC source they are mostly fast enough to cause audible hum on optical audio playback such as on film projection, xenon flash lamps are used for medium- and high-intensity strobe applications. Sufficiently rapid or bright flashing may require active cooling such as forced-air or water cooling to prevent the xenon flash lamp from melting. Joseph Plateau of Belgium is generally credited with the invention of the stroboscope in 1832, Plateau called his device the Phenakistoscope. There was a simultaneous and independent invention of the device by the Austrian Simon Ritter von Stampfer, which he named the Stroboscope, the etymology is from the Greek words στρόβος - strobos, meaning whirlpool and σκοπεῖν - skopein, meaning to look at
Stroboscope
–
A bouncing ball captured with a stroboscopic flash at 25 images per second.
Stroboscope
–
1540 Strobolume, a professional grade stroboscope produced by General Radio
Stroboscope
–
Close-up view of the 1540 Strobolume control box
24.
Cold-cathode fluorescent lamp
–
A fluorescent lamp or a 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 which produces ultraviolet light that then causes a phosphor coating on the inside of the lamp to glow. A fluorescent lamp converts electrical energy into useful light much more efficiently than incandescent lamps, the typical luminous efficacy of fluorescent lighting systems is 50–100 lumens per watt, several times the efficacy of incandescent bulbs with comparable light output. Compact fluorescent lamps are now available in the same sizes as incandescents and are used as an energy-saving alternative in homes. Because they contain mercury, many fluorescent lamps are classified as hazardous 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. Fluorescence of certain rocks and other substances had been observed for hundreds of years before its nature was understood, by the middle of the 19th century, experimenters had observed a radiant glow emanating from partially evacuated glass vessels through which an electric current passed. The explanation relied on 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 vacuum pump that evacuated a glass tube to an extent not previously possible. Geissler invented the first gas-discharge lamp, the Geissler tube, consisting of an evacuated glass tube with a metal electrode at either end. When a high voltage was applied between the electrodes, the inside of the lit up with a glow discharge. By putting different chemicals inside, the tubes could be made to produce a variety of colors, more important, however, was its contribution to scientific research. One of 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 and 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 a Geissler tube and he went on to apply thin coatings of luminescent materials to the surfaces of these tubes. Fluorescence occurred, but the tubes were very inefficient and had an operating life. Inquiries that began with the Geissler tube continued as even better vacuums were produced, the most famous was the evacuated tube used for scientific research by William Crookes. That tube was evacuated by 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 Roentgen. While Becquerel was interested primarily in conducting research into fluorescence. Although Edison lost interest in fluorescent lighting, one of his employees was able to create a gas-based lamp that achieved a measure of commercial success
Cold-cathode fluorescent lamp
–
Fluorescent lamps
Cold-cathode fluorescent lamp
–
Top, two compact fluorescent lamps. Bottom, two fluorescent tube lamps. A matchstick, left, is shown for scale.
Cold-cathode fluorescent lamp
–
Compact fluorescent lamp with
electronic ballast
Cold-cathode fluorescent lamp
–
Typical F71T12 100 W bi-pin lamp used in tanning beds. The (Hg) symbol indicates that this lamp contains
mercury. In the US, this symbol is now required on all fluorescent lamps that contain mercury.
25.
Fluorescence
–
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence, in most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation. Fluorescent materials cease to glow immediately when the radiation source stops, unlike phosphorescence, Fluorescence also occurs frequently in nature in some minerals and in various biological states in many branches of the animal kingdom. An early observation of fluorescence was described in 1560 by Bernardino de Sahagún and it was derived from the wood of two tree species, Pterocarpus indicus and Eysenhardtia polystachya. The chemical compound responsible for this fluorescence is matlaline, which is the product of one of the flavonoids found in this wood. The name was derived from the fluorite, some examples of which contain traces of divalent europium. In a key experiment he used a prism to isolate ultraviolet radiation from sunlight, the specific frequencies of exciting and emitted light are dependent on the particular system. S0 is called the state of the fluorophore, and S1 is its first excited singlet state. A molecule in S1 can relax by various competing pathways and it can undergo non-radiative relaxation in which the excitation energy is dissipated as heat to the solvent. Excited organic molecules can also relax via conversion to a triplet state, relaxation from S1 can also occur through interaction with a second molecule through fluorescence quenching. Molecular oxygen is an extremely efficient quencher of fluorescence just because of its unusual triplet ground state, in most cases, the emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation, this phenomenon is known as the Stokes shift. The emitted radiation may also be of the wavelength as the absorbed radiation. Molecules that are excited through light absorption or via a different process can transfer energy to a second sensitized molecule, the fluorescence quantum yield gives the efficiency of the fluorescence process. It is defined as the ratio of the number of photons emitted to the number of photons absorbed, Φ = Number of photons emitted Number of photons absorbed The maximum fluorescence quantum yield is 1.0, each photon absorbed results in a photon emitted. Compounds with quantum yields of 0.10 are still considered quite fluorescent, thus, if the rate of any pathway changes, both the excited state lifetime and the fluorescence quantum yield will be affected. Fluorescence quantum yields are measured by comparison to a standard, the quinine salt quinine sulfate in a sulfuric acid solution is a common fluorescence standard. The fluorescence lifetime refers to the time the molecule stays in its excited state before emitting a photon. This is an instance of exponential decay, various radiative and non-radiative processes can de-populate the excited state
Fluorescence
–
Fluorescent minerals emit visible light when exposed to
ultraviolet light
Fluorescence
–
Lignum nephriticum cup made from the wood of the narra tree (
Pterocarpus indicus), and a flask containing its fluorescent
solution
Fluorescence
–
Matlaline, the fluorescent substance in the wood of the tree Eysenhardtia polystachya
Fluorescence
–
Aequoria victoria, biofluorescent jellyfish known for GFP.
26.
Backlight
–
A backlight is a form of illumination used in liquid crystal displays. As LCDs do not produce light by themselves, they need illumination to produce a visible image, backlights illuminate the LCD from the side or back of the display panel, unlike frontlights, which are placed in front of the LCD. A review of some early backlighting schemes for LCDs is given in a report Engineering, simple types of LCDs such as in pocket calculators are built without an internal light source, requiring external light sources to convey the display image to the user. Most LCD screens, however, are built with a light source. Such screens consist of several layers, the backlight is usually the first layer from the back. Light valves then vary the amount of light reaching the eye, most use a fixed polarizing filter and a switching one, to block the undesired light. Monochrome LCDs typically have yellow, green, blue, or white backlights, colored LED backlighting is most commonly used in small, inexpensive LCD panels. White LED backlighting is becoming dominant, ELP backlighting is often used for larger displays or when even backlighting is important, it can also be either colored or white. An ELP must be driven by high voltage AC power. CCFL backlights are used on larger displays such as monitors, and are typically white in color. Incandescent backlighting were used by early LCD panels to achieve high brightness, the heat generated by incandescent bulbs typically requires the bulbs to be mounted away from the display to prevent damage. Due to the disadvantages in comparison with LED illumination, LED backlighting is becoming more popular, LED backlighting in color screens comes in two varieties, white LED backlights and RGB LED backlights. White LEDs are used most often in notebooks and desktop screens, a white LED is typically a blue LED with broad spectrum yellow phosphor to result in the emission of white light. However, because the spectral curve peaks at yellow, it is a match to the transmission peaks of the red. This causes the red and green primaries to shift toward yellow, RGB LEDs consist of a red, a blue, and a green LED and can be controlled to produce different color temperatures of white. RGB LEDs can deliver an enormous color gamut to screens, when using three separate LEDs the backlight can produce a color spectrum that closely matches the color filters in the LCD pixels themselves. In this way, the passband can be narrowed so that each color component lets only a very narrow band of spectrum through the LCD. This improves the efficiency of the display since less light is blocked when white is displayed, also, the actual red, green, and blue points can be moved farther out so that the display is capable of reproducing more vivid colors
Backlight
–
18 parallel CCFLs as backlight for an LCD TV
27.
LCD
–
A liquid-crystal display is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals. Liquid crystals do not emit light directly, instead using a backlight or reflector to produce images in color or monochrome and they use the same basic technology, except that arbitrary images are made up of a large number of small pixels, while other displays have larger elements. LCDs are used in a range of applications including computer monitors, televisions, instrument panels, aircraft cockpit displays. Small LCD screens are common in consumer devices such as digital cameras, watches, calculators. LCD screens are used on consumer electronics products such as DVD players, video game devices. LCD screens have replaced heavy, bulky cathode ray tube displays in all applications. LCD screens are available in a range of screen sizes than CRT and plasma displays, with LCD screens available in sizes ranging from tiny digital watches to huge. Since LCD screens do not use phosphors, they do not suffer image burn-in when an image is displayed on a screen for a long time. LCDs are, however, susceptible to image persistence, the LCD screen is more energy-efficient and can be disposed of more safely than a CRT can. Its low electrical power consumption enables it to be used in battery-powered electronic equipment more efficiently than CRTs can be, by 2008, annual sales of televisions with LCD screens exceeded sales of CRT units worldwide, and the CRT became obsolete for most purposes. Without the liquid crystal between the filters, light passing through the first filter would be blocked by the second polarizer. Before an electric field is applied, the orientation of the molecules is determined by the alignment at the surfaces of electrodes. In a twisted nematic device, the surface alignment directions at the two electrodes are perpendicular to other, and so the molecules arrange themselves in a helical structure. This induces the rotation of the polarization of the incident light, and this light will then be mainly polarized perpendicular to the second filter, and thus be blocked and the pixel will appear black. By controlling the voltage applied across the liquid crystal layer in each pixel, color LCD systems use the same technique, with color filters used to generate red, green, and blue pixels. The optical effect of a TN device in the state is far less dependent on variations in the device thickness than that in the voltage-off state. Because of this, TN displays with low content and no backlighting are usually operated between crossed polarizers such that they appear bright with no voltage. When no image is displayed, different arrangements are used, for this purpose, TN LCDs are operated between parallel polarizers, whereas IPS LCDs feature crossed polarizers
LCD
–
LCD with top polarizer removed from device and placed on top, such that the top and bottom polarizers are perpendicular.
LCD
–
Polarizing filter film with a vertical axis to polarize light as it enters.
LCD
–
18 parallel CCFLs as backlight for a 42-inch LCD TV
LCD
–
A pink elastomeric connector mating an LCD panel to circuit board traces, shown next to a centimeter-scale ruler. (The conductive and insulating layers in the black stripe are very small, click on the image for more detail.)
28.
Alternating current
–
Alternating current, is an electric current which periodically reverses direction, whereas direct current flows only in one direction. A common source of DC power is a cell in a flashlight. The abbreviations AC and DC are often used to mean simply alternating and direct, the usual waveform of alternating current in most electric power circuits is a sine wave. In certain applications, different waveforms are used, such as triangular or square waves, audio and radio signals carried on electrical wires are also examples of alternating current. These types of alternating current carry information encoded onto the AC signal and these currents typically alternate at higher frequencies than those used in power transmission. Electrical energy is distributed as alternating current because AC voltage may be increased or decreased with a transformer, use of a higher voltage leads to significantly more efficient transmission of power. The power losses in a conductor are a product of the square of the current and this means that when transmitting a fixed power on a given wire, if the current is halved, the power loss will be four times less. Power is often transmitted at hundreds of kilovolts, and transformed to 100–240 volts for domestic use, high voltages have disadvantages, such as the increased insulation required, and generally increased difficulty in their safe handling. In a power plant, energy is generated at a convenient voltage for the design of a generator, near the loads, the transmission voltage is stepped down to the voltages used by equipment. Consumer voltages vary somewhat depending on the country and size of load, the voltage delivered to equipment such as lighting and motor loads is standardized, with an allowable range of voltage over which equipment is expected to operate. Standard power utilization voltages and percentage tolerance vary in the different mains power systems found in the world, high-voltage direct-current electric power transmission systems have become more viable as technology has provided efficient means of changing the voltage of DC power. HVDC systems, however, tend to be expensive and less efficient over shorter distances than transformers. Three-phase electrical generation is very common, the simplest way is to use three separate coils in the generator stator, physically offset by an angle of 120° to each other. Three current waveforms are produced that are equal in magnitude and 120° out of phase to each other, if coils are added opposite to these, they generate the same phases with reverse polarity and so can be simply wired together. In practice, higher pole orders are commonly used, for example, a 12-pole machine would have 36 coils. The advantage is that lower rotational speeds can be used to generate the same frequency, for example, a 2-pole machine running at 3600 rpm and a 12-pole machine running at 600 rpm produce the same frequency, the lower speed is preferable for larger machines. If the load on a system is balanced equally among the phases. Even in the worst-case unbalanced load, the current will not exceed the highest of the phase currents
Alternating current
–
High voltage transmission lines deliver power from
electric generation plants over long distances using alternating current. These particular lines are located in eastern
Utah.
Alternating current
–
Alternating current (green curve). The horizontal axis measures time; the vertical, current or voltage.
Alternating current
–
The prototype of ZBD. transformer is on display at the Széchenyi István Memorial Exhibition,
Nagycenk,
Hungary
Alternating current
29.
Electron
–
The electron is a subatomic particle, symbol e− or β−, with a negative elementary electric charge. Electrons belong to the first generation of the lepton particle family, the electron has a mass that is approximately 1/1836 that of the proton. Quantum mechanical properties of the include a intrinsic angular momentum of a half-integer value, expressed in units of the reduced Planck constant. As it is a fermion, no two electrons can occupy the same state, in accordance with the Pauli exclusion principle. Like all elementary particles, electrons exhibit properties of particles and waves, they can collide with other particles and can be diffracted like light. Since an electron has charge, it has an electric field. Electromagnetic fields produced from other sources will affect the motion of an electron according to the Lorentz force law, electrons radiate or absorb energy in the form of photons when they are accelerated. Laboratory instruments are capable of trapping individual electrons as well as electron plasma by the use of electromagnetic fields, special telescopes can detect electron plasma in outer space. Electrons are involved in applications such as electronics, welding, cathode ray tubes, electron microscopes, radiation therapy, lasers, gaseous ionization detectors. Interactions involving electrons with other particles are of interest in fields such as chemistry. The Coulomb force interaction between the positive protons within atomic nuclei and the negative electrons without, allows the composition of the two known as atoms, ionization or differences in the proportions of negative electrons versus positive nuclei changes the binding energy of an atomic system. The exchange or sharing of the electrons between two or more atoms is the cause of chemical bonding. In 1838, British natural philosopher Richard Laming first hypothesized the concept of a quantity of electric charge to explain the chemical properties of atoms. Irish physicist George Johnstone Stoney named this charge electron in 1891, electrons can also participate in nuclear reactions, such as nucleosynthesis in stars, where they are known as beta particles. Electrons can be created through beta decay of isotopes and in high-energy collisions. The antiparticle of the electron is called the positron, it is identical to the electron except that it carries electrical, when an electron collides with a positron, both particles can be totally annihilated, producing gamma ray photons. The ancient Greeks noticed that amber attracted small objects when rubbed with fur, along with lightning, this phenomenon is one of humanitys earliest recorded experiences with electricity. In his 1600 treatise De Magnete, the English scientist William Gilbert coined the New Latin term electricus, both electric and electricity are derived from the Latin ēlectrum, which came from the Greek word for amber, ἤλεκτρον
Electron
–
A beam of electrons deflected in a circle by a magnetic field
Electron
–
Hydrogen atom
orbitals at different energy levels. The brighter areas are where you are most likely to find an electron at any given time.
Electron
–
Robert Millikan
Electron
–
A
lightning discharge consists primarily of a flow of electrons. The electric potential needed for lightning may be generated by a triboelectric effect.
30.
Fluorescent lamp
–
A fluorescent lamp or a 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 which produces ultraviolet light that then causes a phosphor coating on the inside of the lamp to glow. A fluorescent lamp converts electrical energy into useful light much more efficiently than incandescent lamps, the typical luminous efficacy of fluorescent lighting systems is 50–100 lumens per watt, several times the efficacy of incandescent bulbs with comparable light output. Compact fluorescent lamps are now available in the same sizes as incandescents and are used as an energy-saving alternative in homes. Because they contain mercury, many fluorescent lamps are classified as hazardous 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. Fluorescence of certain rocks and other substances had been observed for hundreds of years before its nature was understood, by the middle of the 19th century, experimenters had observed a radiant glow emanating from partially evacuated glass vessels through which an electric current passed. The explanation relied on 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 vacuum pump that evacuated a glass tube to an extent not previously possible. Geissler invented the first gas-discharge lamp, the Geissler tube, consisting of an evacuated glass tube with a metal electrode at either end. When a high voltage was applied between the electrodes, the inside of the lit up with a glow discharge. By putting different chemicals inside, the tubes could be made to produce a variety of colors, more important, however, was its contribution to scientific research. One of 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 and 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 a Geissler tube and he went on to apply thin coatings of luminescent materials to the surfaces of these tubes. Fluorescence occurred, but the tubes were very inefficient and had an operating life. Inquiries that began with the Geissler tube continued as even better vacuums were produced, the most famous was the evacuated tube used for scientific research by William Crookes. That tube was evacuated by 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 Roentgen. While Becquerel was interested primarily in conducting research into fluorescence. Although Edison lost interest in fluorescent lighting, one of his employees was able to create a gas-based lamp that achieved a measure of commercial success
Fluorescent lamp
–
Fluorescent lamps
Fluorescent lamp
–
Top, two compact fluorescent lamps. Bottom, two fluorescent tube lamps. A matchstick, left, is shown for scale.
Fluorescent lamp
–
Compact fluorescent lamp with
electronic ballast
Fluorescent lamp
–
Typical F71T12 100 W bi-pin lamp used in tanning beds. The (Hg) symbol indicates that this lamp contains
mercury. In the US, this symbol is now required on all fluorescent lamps that contain mercury.
