1.
Volt
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The volt is the derived unit for electric potential, electric potential difference, and electromotive force. One volt is defined as the difference in potential between two points of a conducting wire when an electric current of one ampere dissipates one watt of power between those points. It is also equal to the difference between two parallel, infinite planes spaced 1 meter apart that create an electric field of 1 newton per coulomb. Additionally, it is the difference between two points that will impart one joule of energy per coulomb of charge that passes through it. It can also be expressed as amperes times ohms, watts per ampere, or joules per coulomb, for the Josephson constant, KJ = 2e/h, the conventional value KJ-90 is used, K J-90 =0.4835979 GHz μ V. This standard is typically realized using an array of several thousand or tens of thousands of junctions. Empirically, several experiments have shown that the method is independent of device design, material, measurement setup, etc. in the water-flow analogy sometimes used to explain electric circuits by comparing them with water-filled pipes, voltage is likened to difference in water pressure. Current is proportional to the diameter of the pipe or the amount of water flowing at that pressure. A resistor would be a reduced diameter somewhere in the piping, the relationship between voltage and current is defined by Ohms Law. Ohms Law is analogous to the Hagen–Poiseuille equation, as both are linear models relating flux and potential in their respective systems, the voltage produced by each electrochemical cell in a battery is determined by the chemistry of that cell. Cells can be combined in series for multiples of that voltage, mechanical generators can usually be constructed to any voltage in a range of feasibility. High-voltage electric power lines,110 kV and up Lightning, Varies greatly. Volta had determined that the most effective pair of metals to produce electricity was zinc. In 1861, Latimer Clark and Sir Charles Bright coined the name volt for the unit of resistance, by 1873, the British Association for the Advancement of Science had defined the volt, ohm, and farad. In 1881, the International Electrical Congress, now the International Electrotechnical Commission and they made the volt equal to 108 cgs units of voltage, the cgs system at the time being the customary system of units in science. At that time, the volt was defined as the difference across a conductor when a current of one ampere dissipates one watt of power. The international volt was defined in 1893 as 1/1.434 of the emf of a Clark cell and this definition was abandoned in 1908 in favor of a definition based on the international ohm and international ampere until the entire set of reproducible units was abandoned in 1948. Prior to the development of the Josephson junction voltage standard, the volt was maintained in laboratories using specially constructed batteries called standard cells
2.
Fluorescent lamp
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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
3.
Electrical connector
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An electrical connector, is an electro-mechanical device used to join electrical terminations and create an electrical circuit. Electrical connectors consist of plugs and jacks, the connection may be temporary, as for portable equipment, require a tool for assembly and removal, or serve as a permanent electrical joint between two wires or devices. An adapter can be used to bring together dissimilar connectors. There are hundreds of types of electrical connectors, connectors may join two lengths of flexible copper wire or cable, or connect a wire or cable to an electrical terminal. In computing, a connector can also be known as a physical interface. Cable glands, known as cable connectors in the US, connect wires to devices rather than electrically and are distinct from quick-disconnects performing the latter. It is usually desirable for a connector to be easy to visually, rapid to assemble, require only simple tooling. In some cases an equipment manufacturer might choose a connector specifically because it is not compatible with those other sources. No single connector has all the properties, the proliferation of types is a reflection of differing requirements. Fretting is a failure mode in electrical connectors that have not been specifically designed to prevent it. Many connectors are keyed, with some mechanical component which prevents mating except with a correctly oriented matching connector, some connector housings are designed with locking mechanisms to prevent inadvertent disconnection or poor environmental sealing. Locking mechanism designs include locking levers of various sorts, screw locking, a terminal is a simple type of electrical connector that connects two or more wires to a single connection point. Wire nuts are another type of single point connector, terminal blocks provide a convenient means of connecting individual electrical wires without a splice or physically joining the ends. They are usually used to connect wiring among various items of equipment within an enclosure or to make connections among individually enclosed items. Since terminal blocks are available for a wide range of wire sizes and terminal quantity. One type of terminal block accepts wires that are prepared only by removing a short length of insulation from the end, another type accepts wires that have ring or spade terminal lugs crimped onto the wires. Printed circuit board mounted terminal blocks allow individual wires to be connected to the circuit board, a general type of connector that simply screws or clamps bare wire to a post, such connectors are frequently used in electronic test equipment and audio. Many, but not all binding posts will also accept a banana connector plug, since stripping the insulation from wires is time-consuming, many connectors intended for rapid assembly use insulation-displacement connectors so that insulation need not be removed from the wire
4.
Calibration
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Calibration in measurement technology and metrology is the comparison of measurement values delivered by a device under test with those of a calibration standard of known accuracy. Such a standard could be another measurement device of known accuracy, strictly, the term calibration means just the act of comparison, and does not include any subsequent adjustment. The calibration standard is normally traceable to a national standard held by a National Metrological Institute and this definition states that the calibration process is purely a comparison, but introduces the concept of Measurement uncertainty in relating the accuracies of the device under test and the standard. The increasing need for accuracy and uncertainty and the need to have consistent. In many countries a National Metrology Institute will exist which will maintain primary standards of measurement which will be used to provide traceability to customers instruments by calibration. The NMI supports the metrological infrastructure in that country by establishing an unbroken chain, examples of National Metrology Institutes are NPL in the UK, NIST in the United States, PTB in Germany and many others. This may be done by national standards laboratories operated by the government or by private firms offering metrology services, quality management systems call for an effective metrology system which includes formal, periodic, and documented calibration of all measuring instruments. ISO9000 and ISO17025 standards require that these actions are to a high level. To communicate the quality of a calibration the calibration value is often accompanied by a traceable uncertainty statement to a confidence level. This is evaluated through careful uncertainty analysis, some times a DFS is required to operate machinery in a degraded state. Whenever this does happen, it must be in writing and authorized by a manager with the assistance of a calibration technician. Measuring devices and instruments are categorized according to the quantities they are designed to measure. These vary internationally, e. g. NIST 150-2G in the U. S. the standard instrument for each test device varies accordingly, e. g. a dead weight tester for pressure gauge calibration and a dry block temperature tester for temperature gauge calibration. g. This is the perception of the instruments end-user, however, very few instruments can be adjusted to exactly match the standards they are compared to. For the vast majority of calibrations, the process is actually the comparison of an unknown to a known. The calibration process begins with the design of the instrument that needs to be calibrated. The design has to be able to hold a calibration through its calibration interval, in other words, the design has to be capable of measurements that are within engineering tolerance when used within the stated environmental conditions over some reasonable period of time. Having a design with these characteristics increases the likelihood of the measuring instruments performing as expected
5.
General Electric
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General Electric, often abbreviated as GE, is an American multinational conglomerate corporation incorporated in New York and headquartered in Boston, Massachusetts. In 2011, GE ranked among the Fortune 500 as the 68th-largest firm in the U. S. by gross revenue, as of 2012, the company was listed the fourth-largest in the world among the Forbes Global 2000, further metrics being taken into account. The Nobel Prize has twice been awarded to employees of General Electric, Irving Langmuir in 1932, on January 13,2016, it was announced that GE will be moving its corporate headquarters from Fairfield, Connecticut to the South Boston Waterfront neighborhood of Boston, Massachusetts. The first group of workers arrived in the summer of 2016, morgan and the Vanderbilt family for Edisons lighting experiments. The new company also acquired Sprague Electric Railway & Motor Company in the same year, both plants continue to operate under the GE banner to this day. The company was incorporated in New York, with the Schenectady plant used as headquarters for years thereafter. Around the same time, General Electrics Canadian counterpart, Canadian General Electric, was formed, in 1896, General Electric was one of the original 12 companies listed on the newly formed Dow Jones Industrial Average. After 120 years, it is the one of the original companies still listed on the Dow index. In 1911, General Electric absorbed the National Electric Lamp Association into its lighting business, GE established its lighting division headquarters at Nela Park in East Cleveland, Ohio. Nela Park is still the headquarters for GEs lighting business, owen D. Young, through GE, founded the Radio Corporation of America in 1919 to further international radio. GE used RCA as its retail arm for radio sales from 1919, in 1927, Ernst Alexanderson of GE made the first demonstration of his television broadcasts at his General Electric Realty Plot home at 1132 Adams Rd, Schenectady, NY. The sound was broadcast on GEs WGY, experimental television station W2XAD evolved into station WRGB which—along with WGY and WGFM —was owned and operated by General Electric until 1983. GEs history of working with turbines in the field gave them the engineering know-how to move into the new field of aircraft turbosuperchargers. Led by Sanford Alexander Moss, GE introduced the first superchargers during World War I, superchargers became indispensable in the years immediately prior to World War II, and GE was the world leader in exhaust-driven supercharging when the war started. This experience, in turn, made GE a natural selection to develop the Whittle W.1 jet engine that was demonstrated in the United States in 1941, GE ranked ninth among United States corporations in the value of wartime production contracts. In 2002, GE acquired the assets of Enron during its bankruptcy proceedings. Some consumers boycotted GE light bulbs, refrigerators and other products in the 1980s and 1990s to protest GEs role in weapons production. With IBM, Burroughs, NCR, Control Data Corporation, Honeywell, RCA and UNIVAC, GE had a line of general purpose and special purpose computers
6.
Philips
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Koninklijke Philips N. V. is a Dutch technology company headquartered in Amsterdam with primary divisions focused in the areas of electronics, healthcare and lighting. It was founded in Eindhoven in 1891, by Gerard Philips and it is one of the largest electronics companies in the world and employs around 105,000 people across more than 60 countries. Philips is organized into three divisions, Philips Consumer Lifestyle, Philips Healthcare and Philips Lighting. As of 2012, Philips was the largest manufacturer of lighting in the world measured by applicable revenues, Philips said it would seek damages for breach of contract in the US$200-million sale. In April 2016, the International Court of Arbitration ruled in favour of Philips, Philips has a primary listing on the Euronext Amsterdam stock exchange and is a component of the Euro Stoxx 50 stock market index. It has a listing on the New York Stock Exchange. The Philips Company was founded in 1891, by Gerard Philips and this first factory has been adapted and is used as a museum. In 1895, after a difficult first few years and near bankruptcy, though he had earned a degree in engineering, Anton started work as a sales representative, soon, however, he began to contribute many important business ideas. After Gerard and Anton Philips changed their business by founding the Philips corporation. In the 1920s, the company started to other products. In 1939, they introduced their electric razor, the Philishave, the Chapel is a radio with built-in loudspeaker, which was designed during the early 1930s. On 11 March 1927, Philips went on the air with shortwave radio station PCJJ which was joined in 1929 by sister station PHOHI, PHOHI broadcast in Dutch to the Dutch East Indies while PCJJ broadcast in English, Spanish and German to the rest of the world. The international program on Sundays commenced in 1928, with host Eddie Startz hosting the Happy Station show, broadcasts from the Netherlands were interrupted by the German invasion in May 1940. The Germans commandeered the transmitters in Huizen to use for pro-Nazi broadcasts, some originating from Germany, Philips Radio was absorbed shortly after liberation when its two shortwave stations were nationalised in 1947 and renamed Radio Netherlands Worldwide, the Dutch International Service. Some PCJ programs, such as Happy Station, continued on the new station, by the late 1940s, the Type 10 was ready to be handed over to Philips subsidiary Johan de Witt in Dordrecht to be produced and incorporated into a generator set as originally planned. The result, rated at 180/200 W electrical output from a bore, approximately 150 of these sets were eventually produced. However, they filed a number of patents and amassed a wealth of information. The first Philips shaver was introduced in the 1930s, and was simply called “The Philishave”, in the USA, it was called the “Norelco”, which remains a part of their product line today
7.
Sylvania Electric Products
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Sylvania Electric Products was a U. S. manufacturer of diverse electrical equipment, including at various times radio transceivers, vacuum tubes, semiconductors, and mainframe computers. They were one of the involved in the development of the COBOL programming language. The Hygrade Sylvania Corporation was formed when NILCO, Sylvania and Hygrade Lamp Company merged into one company in 1931, in 1939, Hygrade Sylvania started preliminary research on fluorescent technology, and later that year, demonstrated the first linear, or tubular, fluorescent lamp. It was featured at the 1939 New York Worlds Fair, Sylvania was also a manufacturer of both vacuum tubes and transistors. In 1942, the changed its name to Sylvania Electric Products Inc. All were manufactured and distributed under the brand name GTE Sylvania, GTE Sylvania contributed to the technological advancement of electrical distribution products in the late 1970s with several interesting product features. At the time, they were the supplier of vacuum cast coil transformers, manufactured in their Hampton. They also developed the first medium voltage 3 phase panel that could survive a short across two phases. Their patented design used bus bar encapsulated in a coating of epoxy. By 1981 GTE had made the decision to exit the electrical equipment market and began selling off its product lines. The Challenger line, mostly manufactured at the time in Jackson, Mississippi was sold to an officer of GTE. Challenger flourished, and was sold to Westinghouse, and later Eaton Corporation. By the mid 1980s, the GTE Sylvania electrical equipment product line, in 1993 GTE exited the lighting business to concentrate on its core telecomms operations. The European, Asian and Latin American operations are now under the ownership of Havells Sylvania, with the acquisition of the North American division by Osram GmbH in January 1993 Osram Sylvania Inc. was established. In the early 1980s, GTE Sylvania sold the rights to the name Sylvania and Philco for use on consumer electronics equipment only and this marked the end of Sylvanias TV production in Batavia, New York, USA, and Smithfield, North Carolina, USA. The Sylvania Smithfield plant later became Channel Master, the rights to the Sylvania name in many countries are held by the U. S. subsidiary of the German company Osram. The Sylvania brand name is owned worldwide, apart from Australia, Canada, Mexico, Thailand, New Zealand, Puerto Rico and the USA, by Havells Sylvania, headquartered in London. Osram Sylvania manufactures and markets a range of lighting products for homes, business
8.
Dimmer
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Dimmers are devices used to lower the brightness of a light. By changing the waveform applied to the lamp, it is possible to lower the intensity of the light output. More specialized equipment is needed to dim fluorescent, mercury vapor, solid state, Dimmers range in size from small units the size of a light switch used for domestic lighting to high power units used in large theatre or architectural lighting installations. Small domestic dimmers are generally controlled, although remote control systems are available. Modern professional dimmers are controlled by a digital control system like DMX or DALI. In newer systems, these protocols are used in conjunction with ethernet. In the professional lighting industry, changes in intensity are called fades, Dimmers with direct manual control had a limit on the speed they could be varied at but this issue has been largely eliminated with modern digital units. Modern dimmers are built from semiconductors instead of variable resistors, because they have higher efficiency, a variable resistor would dissipate power as heat and acts as a voltage divider. Since semiconductor or solid-state dimmers switch quickly between a low resistance on state and a high resistance off state, they dissipate very little compared with the controlled load. Early dimmers were directly controlled through the manipulation of large dimmer panels. In 1896, Granville Woods patented his Safety Dimmer, which greatly reduced wasted energy by reducing the amount of energy generated to match desired demand rather than burning off unwanted energy. In 1966, Eugene Alessio patented a light bulb socket adapter for adjusting a light level on a light bulb using a triac. To house this device, he decided on a 2-inch round device with one end capable of being screwed into a light bulb socket, when solid-state dimmers came into use, analog remote control systems became feasible. The wire for the systems was much smaller than the heavy power cables of previous lighting systems. Each dimmer had its own control wires, resulting in many leaving the lighting control location. Dimmers based on rheostats were inefficient since they would dissipate a significant portion of the rating of the load as heat. They were large and required plenty of cooling air, because their dimming effect depended a great deal on the total load applied to each rheostat, the load needed to be matched fairly carefully to the power rating of the rheostat. The closer the contacts to other, the more voltage was available for the light
9.
Lighting control console
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A lighting control console is an electronic device used in theatrical lighting design to control multiple lights at once. They are used throughout the entertainment industry and are placed at the Front of House position or in a control booth. All lighting control consoles can control dimmers which control the intensity of the lights, many modern consoles can control Intelligent lighting, fog machines and hazers, and other special effects devices. Some consoles can also interface with other performance hardware to improve synchronization or unify their control. Lighting consoles communicate with the dimmers and other devices in the system via an electronic control protocol. Consoles vary in size and complexity, from small preset boards to dedicated moving light consoles, most consoles accept MIDI Show Control signals and commands to allow show control systems to integrate their capabilities into more complex shows. Preset boards are the most basic lighting consoles—and also the most prevalent in smaller installations and they consist of two or more identical fader banks, called scenes. The faders on these scenes can be manually adjusted, each scene has the same number of channels which control the same dimmers. So the console operator can build a scene offline or in blind, generally, at least with a preset board, the operator has a cue sheet for each scene, which is a diagram of the board with the faders in their positions as determined by the lighting designer. The operator sets the faders into their positions based on the cue sheets, typically during a cue, the operator sets the next scene. Then, the operator makes the transition between the scenes using the cross-fader, Preset boards are not as prevalent since the advent of digital memory consoles, which can store scenes digitally, and are generally much less cumbersome but more expensive than preset boards. However, for small setups such as that of a DJ, they remain the board of choice for their simple to use interface and this is however not recommended since it is a long, drawn-out, and cumbersome process. Memory-based consoles have become popular in almost all larger installations. This type of controller has almost completely replaced preset consoles as controllers of choice and they also allow for lighting cues to contain larger channel counts due to the same time savings gained from not physically moving individual channel faders. Many memory consoles have a bank of faders and these faders can be programmed to control a single channel or a group of channels. The console may also have provision to operate in analog to a desk for programming scenes or live control. On some more advanced consoles, faders can be used to control effects, chases, moving Light Controllers are another step up in sophistication from Memory Consoles. As well as being capable of controlling ordinary luminares via dimmers, on midrange controllers, these are usually provided as a section separate from main Preset and Cue stack controls
10.
DMX512
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DMX512 is a standard for digital communication networks that are commonly used to control stage lighting and effects. It was originally intended as a method for controlling light dimmers. It soon became the method for linking controllers to dimmers and special effects devices such as fog machines. DMX has also expanded to uses in interior and architectural lighting. DMX can now be used to control almost anything, reflecting its popularity in theaters, DMX512 employs EIA-485 differential signaling at its physical layer, in conjunction with a variable-size, packet-based communication protocol. DMX512 does not include automatic error checking and correction, and so is not a control for hazardous applications. False triggering may be caused by interference, static electricity discharges, improper cable termination, excessively long cables. Developed by the Engineering Commission of United States Institute for Theatre Technology, in 1998 the Entertainment Services and Technology Association began a revision process to develop the standard as an ANSI standard. It was revised again in 2008, and is the current standard known as E1.11 –2008, USITT DMX512-A, in January 2011 ESTA merged with PLASA, a similar organization in the UK. The new organization is called Plasa, all ESTA standards are now maintained by Plasa. A DMX512 network employs a multi-drop bus topology with nodes strung together in what is called a daisy chain. A network consists of a single DMX512 controller – which is the master of the network —, for example, a lighting console is frequently employed as the controller for a network of slave devices such as dimmers, fog machines and intelligent lights. Each slave device has a DMX512 IN connector and usually an OUT connector as well, the controller, which has only an OUT connector, is connected via a DMX512 cable to the IN connector of the first slave. A second cable then links the OUT or THRU connector of the first slave to the IN connector of the slave in the chain. For example, the diagram below shows a simple network consisting of a controller. The specification requires a terminator to be connected to the final OUT or THRU connector of the last slave on the daisy chain, which would otherwise be unconnected. A terminator is a male connector with an integral 120 Ω resistor connected across the primary data signal pair. If a secondary data pair is used, a resistor is connected across it as well
11.
Electrical wiring
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Electrical wiring is commonly understood to be an electrical installation for operation by end users within a building, an engineered structure or a designated outdoor location. It includes the cabling and associated such as switches, distribution boards, sockets and light fittings. Such wiring is subject to safety standards for design and installation. Associated circuit protection, control and distribution devices within a buildings wiring system are subject to voltage, current, the International Electrotechnical Commission is attempting to harmonise wiring standards amongst member countries, but significant variations in design and installation requirements still exist. Wiring installation codes and regulations are intended to protect people and property from electrical shock and they are usually based on a model code produced by a national or international standards organisation, such as the IEC. The standard is mandatory in both New Zealand and Australia, therefore, all electrical work covered by the standard must comply, in European countries, an attempt has been made to harmonise national wiring standards in an IEC standard, IEC60364 Electrical Installations for Buildings. Hence national standards follow a system of sections and chapters. However, this standard is not written in language that it can readily be adopted as a national wiring code. Neither is it designed for use by electrical tradesmen and inspectors for testing compliance with national wiring standards. In Germany, DKE is the responsible for the promulgation of electrical standards. DIN VDE0100 is the German wiring regulations document harmonised with IEC60364, the first electrical codes in the United States originated in New York in 1881 to regulate installations of electric lighting. Since 1897 the US National Fire Protection Association, a private non-profit association formed by insurance companies, has published the National Electrical Code, States, counties or cities often include the NEC in their local building codes by reference along with local differences. The NEC is modified every three years and it is a consensus code considering suggestions from interested parties. The proposals are studied by committees of engineers, tradesmen, manufacturer representatives, fire fighters, since 1927, the Canadian Standards Association has produced the Canadian Safety Standard for Electrical Installations, which is the basis for provincial electrical codes. The Canadian code reprints Chapter 13 of IEC60364, but there are no numerical criteria listed in that chapter to assess the adequacy of any electrical installation. Although the US and Canadian national standards deal with the physical phenomena and broadly similar objectives. As part of the North American Free Trade Agreement program, US and Canadian standards are slowly converging toward each other, the 17th edition includes new sections for microgeneration and solar photovoltaic systems. The first edition was published in 1882, to enable wires to be easily and safely identified, all common wiring safety codes mandate a colour scheme for the insulation on power conductors
12.
Direct current
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Direct current is a flow of electrical charge carriers that always takes place in the same direction. The current need not always have the magnitude, but if it is to be defined as dc. This contrasts with alternating current which varies the direction of flow, sources of direct current include power supplies, electrochemical cells and batteries, and photovoltaic cells and panels. The intensity, or amplitude, of a direct current might fluctuate with time, in some such cases the dc has an ac component superimposed on it. An example of this is the output of a cell that receives a modulated light communications signal. A source of dc is sometimes called a dc generator, batteries and various other sources of dc produce a constant voltage. This is called pure dc and can be represented by a straight, the peak and effective values are the same. The peak to peak value is zero because the instantaneous amplitude never changes, in some instances the value of a dc voltage pulsates or oscillates rapidly with time, in a manner similar to the changes in an ac wave. The unfiltered output of a wave or a full wave rectifier. In 1820, Hans Christian Orsted discovered that electrical current creates a magnetic field and this discovery made scientists relate magnetism to the electric phenomena. In 1879, Thomas Edison invented the light bulb. He improved a 50-year-old idea using lower current electricity, a vacuum inside the globe and a small carbonized filament. At that time, the idea of lightning was not new. Edison not only invented an incandescent electric light, but an electric lighting system contained all the necessary elements to make the incandescent light safe, economical. Prior to 1879, direct current electricity had been used in lighting for the outdoors and it was in the 1880s when the modern electric utility industry began. It was an evolution from street lighting systems and from gas and it was located in Lower Manhattan, on Pearl Street. This station provided light and electricity to customers in a one square mile range, the station was called Thomas Edisons Pearl Street Electricity Generating Station. This station introduced four elements of an electric utility system, Efficient distribution, competitive price, reliable central generation
