Protective relay
In electrical engineering, a protective relay is a relay device designed to trip a circuit breaker when a fault is detected.:4 The first protective relays were electromagnetic devices, relying on coils operating on moving parts to provide detection of abnormal operating conditions such as over-current, over-voltage, reverse power flow, over-frequency, under-frequency. Microprocessor-based digital protection relays now emulate the original devices, as well as providing types of protection and supervision impractical with electromechanical relays. Electromechanical relays provide only rudimentary indication of the origin of a fault. In many cases a single microprocessor relay provides functions that would take two or more electromechanical devices. By combining several functions in one case, numerical relays save capital cost and maintenance cost over electromechanical relays. However, due to their long life span, tens of thousands of these "silent sentinels" are still protecting transmission lines and electrical apparatus all over the world.
Important transmission lines and generators have cubicles dedicated to protection, with many individual electromechanical devices, or one or two microprocessor relays. The theory and application of these protective devices is an important part of the education of a power engineer who specializes in power system protection; the need to act to protect circuits and equipment as well as the general public requires protective relays to respond and trip a breaker within a few thousandths of a second. In some instances these clearance times are prescribed in operating rules. A maintenance or testing program is used to determine the performance and availability of protection systems. Based on the end application and applicable legislation, various standards such as ANSI C37.90, IEC255-4, IEC60255-3, IAC govern the response time of the relay to the fault conditions that may occur. Electromechanical protective relays operate by either magnetic attraction, or magnetic induction.:14 Unlike switching type electromechanical relays with fixed and ill-defined operating voltage thresholds and operating times, protective relays have well-established and adjustable time and current operating characteristics.
Protection relays may use arrays of induction disks, shaded-pole,:25 magnets and restraint coils, solenoid-type operators, telephone-relay contacts, phase-shifting networks. Protective relays can be classified by the type of measurement they make.:92 A protective relay may respond to the magnitude of a quantity such as voltage or current. Induction relays can respond to the product of two quantities in two field coils, which could for example represent the power in a circuit. "It is not practical to make a relay that develops a torque equal to the quotient of two a.c. quantities. This, however is not important. Various combinations of "operate torque" and "restraint torque" can be produced in the relay. By use of a permanent magnet in the magnetic circuit, a relay can be made to respond to current in one direction differently from in another; such polarized relays are used on direct-current circuits to detect, for example, reverse current into a generator. These relays can be made bistable, maintaining a contact closed with no coil current and requiring reverse current to reset.
For AC circuits, the principle is extended with a polarizing winding connected to a reference voltage source. Lightweight contacts make for sensitive relays that operate but small contacts can't carry or break heavy currents; the measuring relay will trigger auxiliary telephone-type armature relays. In a large installation of electromechanical relays, it would be difficult to determine which device originated the signal that tripped the circuit; this information is useful to operating personnel to determine the cause of the fault and to prevent its re-occurrence. Relays may be fitted with a "target" or "flag" unit, released when the relay operates, to display a distinctive colored signal when the relay has tripped. Electromechanical relays can be classified into several different types as follows: "Armature"-type relays have a pivoted lever supported on a hinge or knife-edge pivot, which carries a moving contact; these relays may work on either alternating or direct current, but for alternating current, a shading coil on the pole:14 is used to maintain contact force throughout the alternating current cycle.
Because the air gap between the fixed coil and the moving armature becomes much smaller when the relay has operated, the current required to maintain the relay closed is much smaller than the current to first operate it. The "returning ratio" or "differential" is the measure of how much the current must be reduced to reset the relay. A variant application of the attraction principle is the solenoid operator. A reed relay is another example of the attraction principle. "Moving coil" meters use a loop of wire turns in a stationary magnet, similar to a galvanometer but with a contact lever instead of a pointer. These can be made with high sensitivity. Another type of moving coil suspends the coil from two conductive ligaments, allowing long travel of the coil. "Induction" disk meters work by inducing currents in a disk, free to rotate. Induction relays require alternating current.
Electrical engineering
Electrical engineering is a professional engineering discipline that deals with the study and application of electricity and electromagnetism. This field first became an identifiable occupation in the half of the 19th century after commercialization of the electric telegraph, the telephone, electric power distribution and use. Subsequently and recording media made electronics part of daily life; the invention of the transistor, the integrated circuit, brought down the cost of electronics to the point they can be used in any household object. Electrical engineering has now divided into a wide range of fields including electronics, digital computers, computer engineering, power engineering, telecommunications, control systems, radio-frequency engineering, signal processing and microelectronics. Many of these disciplines overlap with other engineering branches, spanning a huge number of specializations such as hardware engineering, power electronics and waves, microwave engineering, electrochemistry, renewable energies, electrical materials science, much more.
See glossary of electrical and electronics engineering. Electrical engineers hold a degree in electrical engineering or electronic engineering. Practising engineers may be members of a professional body; such bodies include the Institute of Electrical and Electronics Engineers and the Institution of Engineering and Technology. Electrical engineers work in a wide range of industries and the skills required are variable; these range from basic circuit theory to the management skills required of a project manager. The tools and equipment that an individual engineer may need are variable, ranging from a simple voltmeter to a top end analyzer to sophisticated design and manufacturing software. Electricity has been a subject of scientific interest since at least the early 17th century. William Gilbert was a prominent early electrical scientist, was the first to draw a clear distinction between magnetism and static electricity, he is credited with establishing the term "electricity". He designed the versorium: a device that detects the presence of statically charged objects.
In 1762 Swedish professor Johan Carl Wilcke invented a device named electrophorus that produced a static electric charge. By 1800 Alessandro Volta had developed the voltaic pile, a forerunner of the electric battery In the 19th century, research into the subject started to intensify. Notable developments in this century include the work of Hans Christian Ørsted who discovered in 1820 that an electric current produces a magnetic field that will deflect a compass needle, of William Sturgeon who, in 1825 invented the electromagnet, of Joseph Henry and Edward Davy who invented the electrical relay in 1835, of Georg Ohm, who in 1827 quantified the relationship between the electric current and potential difference in a conductor, of Michael Faraday, of James Clerk Maxwell, who in 1873 published a unified theory of electricity and magnetism in his treatise Electricity and Magnetism. In 1782 Georges-Louis Le Sage developed and presented in Berlin the world's first form of electric telegraphy, using 24 different wires, one for each letter of the alphabet.
This telegraph connected two rooms. It was an electrostatic telegraph. In 1795, Francisco Salva Campillo proposed an electrostatic telegraph system. Between 1803-1804, he worked on electrical telegraphy and in 1804, he presented his report at the Royal Academy of Natural Sciences and Arts of Barcelona. Salva’s electrolyte telegraph system was innovative though it was influenced by and based upon two new discoveries made in Europe in 1800 – Alessandro Volta’s electric battery for generating an electric current and William Nicholson and Anthony Carlyle’s electrolysis of water. Electrical telegraphy may be considered the first example of electrical engineering. Electrical engineering became a profession in the 19th century. Practitioners had created a global electric telegraph network and the first professional electrical engineering institutions were founded in the UK and USA to support the new discipline. Francis Ronalds created an electric telegraph system in 1816 and documented his vision of how the world could be transformed by electricity.
Over 50 years he joined the new Society of Telegraph Engineers where he was regarded by other members as the first of their cohort. By the end of the 19th century, the world had been forever changed by the rapid communication made possible by the engineering development of land-lines, submarine cables, from about 1890, wireless telegraphy. Practical applications and advances in such fields created an increasing need for standardised units of measure, they led to the international standardization of the units volt, coulomb, ohm and henry. This was achieved at an international conference in Chicago in 1893; the publication of these standards formed the basis of future advances in standardisation in various industries, in many countries, the definitions were recognized in relevant legislation. During these years, the study of electricity was considered to be a subfield of physics since the early electrical technology was considered electromechanical in nature; the Technische Universität Darmstadt founded the world's first department of electrical engineering in 1882.
The first electrical engineering degree program was started at Massachusetts Institute of Technology in the physics department
Incandescent light bulb
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 is protected from oxidation with a glass or fused quartz bulb, filled with inert gas or a vacuum. In a halogen lamp, filament evaporation is slowed by a chemical process that redeposits metal vapor onto the filament, thereby extending its life; the light bulb is supplied with electric current by feed-through terminals or wires embedded in the glass. Most bulbs are used in a socket which provides electrical connections. Incandescent bulbs are manufactured in a wide range of sizes, light output, voltage ratings, from 1.5 volts to about 300 volts. They require no external regulating equipment, have low manufacturing costs, work well on either alternating current or direct current; as a result, the incandescent bulb is used in household and commercial lighting, for portable lighting such as table lamps, car headlamps, flashlights, for decorative and advertising lighting.
Incandescent bulbs are much less efficient than other types of electric lighting. The remaining energy is converted into heat; the luminous efficacy of a typical incandescent bulb for 120 V operation is 16 lumens per watt, compared with 60 lm/W for a compact fluorescent bulb or 150 lm/W for some white LED lamps. 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, the Easy-Bake Oven toy. Incandescent bulbs have short lifetimes compared with other types of lighting. Incandescent bulbs have been replaced in many applications by other types of electric light, such as fluorescent lamps, compact fluorescent lamps, cold cathode fluorescent lamps, high-intensity discharge lamps, light-emitting diode lamps; some jurisdictions, such as the European Union, China and United States, are in the process of phasing out the use of incandescent light bulbs while others, including Colombia, Cuba and Brazil, have prohibited them already.
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 and Thomas Edison. They conclude that Edison's version was able to outstrip the others because of a combination of three factors: an effective incandescent material, a higher vacuum than others were able to achieve and a high resistance that made power distribution from a centralized source economically viable. Historian Thomas Hughes has attributed Edison's success to his development of an entire, integrated system of electric lighting; the lamp was a small component in his system of electric lighting, no more critical to its effective functioning than the Edison Jumbo generator, the Edison main and feeder, the parallel-distribution system. Other inventors with generators and incandescent lamps, with comparable ingenuity and excellence, have long been forgotten because their creators did not preside over their introduction in a system of lighting.
In 1761 Ebenezer Kinnersley demonstrated heating a wire to incandescence. In 1802, Humphry Davy used what he described as "a battery of immense size", consisting of 2,000 cells housed in the basement of the Royal Institution of Great Britain, to create an incandescent light by passing the current through a thin strip of platinum, chosen because the metal had an high melting point, 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, evacuated or semi-evacuated enclosures. Many of these devices were demonstrated and some were patented. In 1835, James Bowman Lindsay demonstrated a constant electric light at a public meeting in Dundee, Scotland, he stated that he could "read a book at a distance of one and a half feet". Lindsay, a lecturer at the Watt Institution in Dundee, Scotland, at the time, had developed a light, not combustible, created no smoke or smell and was less expensive to produce than Davy's platinum-dependent bulb.
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 and passed an electric current through it; the design was based on the concept that the high melting point of platinum would allow it to operate at high temperatures and that the evacuated chamber would contain fewer gas molecules to react with the platinum, improving its longevity. 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, with a design using platinum wires contained within a vacuum
Fuse (electrical)
In electronics and electrical engineering, a fuse is an electrical safety device that operates to provide overcurrent protection of an electrical circuit. Its essential component is a metal wire or strip that melts when too much current flows through it, thereby interrupting the current, it is a sacrificial device. Fuses have been used as essential safety devices from the early days of electrical engineering. Today there are thousands of different fuse designs which have specific current and voltage ratings, breaking capacity and response times, depending on the application; the time and current operating characteristics of fuses are chosen to provide adequate protection without needless interruption. Wiring regulations define a maximum fuse current rating for particular circuits. Short circuits, mismatched loads, or device failure are the prime reasons for fuse operation. A fuse is an automatic means of removing power from a faulty system. Circuit breakers can be used as an alternative to fuses, but have different characteristics.
Breguet recommended the use of reduced-section conductors to protect telegraph stations from lightning strikes. A variety of wire or foil fusible elements were in use to protect telegraph cables and lighting installations as early as 1864. A fuse was patented by Thomas Edison in 1890 as part of his electric distribution system. A fuse consists of a metal strip or wire fuse element, of small cross-section compared to the circuit conductors, mounted between a pair of electrical terminals, enclosed by a non-combustible housing; the fuse is arranged in series to carry all the current passing through the protected circuit. The resistance of the element generates heat due to the current flow; the size and construction of the element is determined so that the heat produced for a normal current does not cause the element to attain a high temperature. If too high a current flows, the element rises to a higher temperature and either directly melts, or else melts a soldered joint within the fuse, opening the circuit.
The fuse element is made of zinc, silver, aluminum, or alloys to provide stable and predictable characteristics. The fuse ideally would carry its rated current indefinitely, melt on a small excess; the element must not be damaged by minor harmless surges of current, must not oxidize or change its behavior after years of service. The fuse elements may be shaped to increase heating effect. In large fuses, current may be divided between multiple strips of metal. A dual-element fuse may contain a metal strip that melts on a short-circuit, contain a low-melting solder joint that responds to long-term overload of low values compared to a short-circuit. Fuse elements may be supported by steel or nichrome wires, so that no strain is placed on the element, but a spring may be included to increase the speed of parting of the element fragments; the fuse element may be surrounded by air, or by materials intended to speed the quenching of the arc. Silica sand or non-conducting liquids may be used. A maximum current that the fuse can continuously conduct without interrupting the circuit.
The speed at which a fuse blows depends on how much current flows through it and the material of which the fuse is made. The operating time decreases as the current increases. Fuses have different characteristics of operating time compared to current. A standard fuse may require twice its rated current to open in one second, a fast-blow fuse may require twice its rated current to blow in 0.1 seconds, a slow-blow fuse may require twice its rated current for tens of seconds to blow. Fuse selection depends on the load's characteristics. Semiconductor devices may use a fast or ultrafast fuse as semiconductor devices heat when excess current flows; the fastest blowing fuses are designed for the most sensitive electrical equipment, where a short exposure to an overload current could be damaging. Normal fast-blow fuses are the most general purpose fuses. A time-delay fuse is designed to allow a current, above the rated value of the fuse to flow for a short period of time without the fuse blowing; these types of fuse are used on equipment such as motors, which can draw larger than normal currents for up to several seconds while coming up to speed.
Manufacturers can provide a plot of current vs time plotted on logarithmic scales, to characterize the device and to allow comparison with the characteristics of protective devices upstream and downstream of the fuse. The I2t rating is related to the amount of energy let through by the fuse element when it clears the electrical fault; this term is used in short circuit conditions and the values are used to perform co-ordination studies in electrical networks. I2t parameters are provided by charts in manufacturer data sheets for each fuse family. For coordination of fuse operation with upstream or downstream devices, both melting I2t and clearing I2t are specified; the melting I2t is proportional to the amount of energy required to begin melting the fuse element. The clearing I2t is proportional to the total energy let through by the fuse; the energy is dependent on current and time for fuses as well as the available fault level and system voltage. Since the I2t rating of the fuse is proportional to the energy it lets through, it is a measure of the thermal damage from the heat and magnetic forces that will be produced by a fault.
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Energy storage
Energy storage is the capture of energy produced at one time for use at a time. A device that stores energy is called an accumulator or battery. Energy comes in multiple forms including radiation, gravitational potential, electrical potential, elevated temperature, latent heat and kinetic. Energy storage involves converting energy from forms that are difficult to store to more conveniently or economically storable forms; some technologies provide short-term energy storage. Bulk energy storage is dominated by hydroelectric dams, both conventional as well as pumped. Common examples of energy storage are the rechargeable battery, which stores chemical energy convertible to electricity to operate a mobile phone, the hydroelectric dam, which stores energy in a reservoir as gravitational potential energy, ice storage tanks, which store ice frozen by cheaper energy at night to meet peak daytime demand for cooling. Fossil fuels such as coal and gasoline store ancient energy derived from sunlight by organisms that died, became buried and over time were converted into these fuels.
Food is a form of energy stored in chemical form. In the twentieth century grid, electrical power was generated by burning fossil fuel; when less power was required, less fuel was burned. Concerns with air pollution, energy imports, global warming have spawned the growth of renewable energy such as solar and wind power. Wind power may be generating at a time when no additional power is needed. Solar power varies with cloud cover and at best is only available during daylight hours, while demand peaks after sunset. Interest in storing power from these intermittent sources grows as the renewable energy industry begins to generate a larger fraction of overall energy consumption. Off grid electrical use was a niche market in the twentieth century, but in the twenty-first century, it has expanded. Portable devices are in use all over the world. Solar panels are now a common sight in the rural settings worldwide. Access to electricity is now a question of economics, not location. Powering transportation without burning fuel, remains in development.
The following list includes a variety of types of energy storage: Energy can be stored in water pumped to a higher elevation using pumped storage methods or by moving solid matter to higher locations. Other commercial mechanical methods include compressing air and flywheels that convert electric energy into kinetic energy and back again when electrical demand peaks. Hydroelectric dams with reservoirs can be operated to provide electricity at times of peak demand. Water is released when demand is high; the net effect is similar to without the pumping loss. While a hydroelectric dam does not directly store energy from other generating units, it behaves equivalently by lowering output in periods of excess electricity from other sources. In this mode, dams are one of the most efficient forms of energy storage, because only the timing of its generation changes. Hydroelectric turbines have a start-up time on the order of a few minutes. Worldwide, pumped-storage hydroelectricity is the largest-capacity form of active grid energy storage available, and, as of March 2012, the Electric Power Research Institute reports that PSH accounts for more than 99% of bulk storage capacity worldwide, representing around 127,000 MW.
PSH energy efficiency varies in practice between 70% and 80%, with claims of up to 87%. At times of low electrical demand, excess generation capacity is used to pump water from a lower source into a higher reservoir; when demand grows, water is released back into a lower reservoir through a turbine, generating electricity. Reversible turbine-generator assemblies act as both a turbine. Nearly all facilities use the height difference between two water bodies. Pure pumped-storage plants shift the water between reservoirs, while the "pump-back" approach is a combination of pumped storage and conventional hydroelectric plants that use natural stream-flow. Compressed air energy storage uses surplus energy to compress air for subsequent electricity generation. Small scale systems have long been used in such applications as propulsion of mine locomotives; the compressed air is stored as a salt dome. Compressed-air energy storage plants can bridge the gap between production load. CAES storage addresses the energy needs of consumers by providing available energy to meet demand.
Renewable energy sources like wind and solar energy have variable resources. As a result, the supplement of other forms of energy is necessary to meet energy demand during periods of decreased resource availability. Compressed-air energy storage plants are capable of taking in the surplus energy output of renewable energy sources during times of energy over-production; this stored energy can be used at a time when demand for electricity increases or energy resource availability decreases. Compression of air creates heat. Expansion requires heat. If no extra heat is added, the air will be much colder after expansion. If the heat generated during compression can be stored and used during expansion, efficiency improves considerably. A CAES system can deal with the heat in three ways. Air storage can be diabatic, or isothermal. Another approach uses compressed air to power vehicles. Flywheel energy storage works by accelerating a rotor to a very
Steel wire armoured cable
Steel wire armoured cable abbreviated as SWA, is a hard-wearing power cable designed for the supply of mains electricity. It is one of a number of armoured electrical cables – which include 11 kV Cable and 33 kV Cable – and is found in underground systems, power networks and cable ducting; the typical construction of an SWA cable can be broken down as follows: Conductor: consists of plain stranded copper Insulation: Cross-linked polyethylene is used in a number of power cables because it has good water resistance and excellent electrical properties. Insulation in cables ensures that conductors and other metal substances do not come into contact with each other. Bedding: Polyvinyl chloride bedding is used to provide a protective boundary between inner and outer layers of the cable. Armour: Steel wire armour provides mechanical protection, which means the cable can withstand higher stresses, be buried directly and used in external or underground projects; the armouring is connected to earth and can sometimes be used as the circuit protective conductor for the equipment supplied by cable.
Sheath: a black PVC sheath holds all components of the cable together and provides additional protection from external stresses. The PVC version of SWA cable, described above, meets the requirements of both British Standard BS 5467 and International Electrotechnical Commission standard IEC 60502, it is known as SWA BS 5467 Cable and it has a voltage rating of 600/1000 V. SWA cable can be referred to more as mains cable, armoured cable, power cable and booklet armoured cable; the name power cable, applies to a wide range of cables including 6381Y, NYCY, NYY-J and 6491X Cable. Steel wire armour is only used on multicore versions of the cable. A multicore cable, as the name suggests, is one; when cable has only one core, aluminium wire armour is used instead of steel wire. This is. A magnetic field is produced by the current in a single core cable; this would induce an electric current in the steel wire. The use of the armour as the means of providing earthing to the equipment supplied by the cable is a matter of debate within the electrical installation industry.
It is sometimes the case that an additional core within the cable is specified as the CPC or an external earth wire is run alongside the cable to serve as the CPC. Primary concerns are the relative conductivity of the armouring compared to the cores and reliability issues. Recent articles by authoritative sources have analysed the practice in detail and concluded that, for the majority of situations, the armouring is adequate to serve as the CPC under UK wiring regulations; the construction of an SWA cable depends on the intended use. When the power cable needs to be installed in a public area, for example, a Low Smoke Zero Halogen equivalent, called SWA BS 6724 Cable must be used. After the King’s Cross fire in London in 1987 it became mandatory to use LSZH sheathing on all London Underground cables – a number of the fatalities were due to toxic gas and smoke inhalation; as a result, LSZH cables are now recommended for use in populated enclosed public areas. This is because they emit low levels of smoke when exposed to fire.
SWA Cable BS 6724 – which meets the requirements of British standard BS 6724 – has LSZH bedding and a black LSZH sheath. Electrical cable Electrical wiring
Michael Faraday
Michael Faraday FRS was an English scientist who contributed to the study of electromagnetism and electrochemistry. His main discoveries include the principles underlying electromagnetic induction and electrolysis. Although Faraday received little formal education, he was one of the most influential scientists in history, it was by his research on the magnetic field around a conductor carrying a direct current that Faraday established the basis for the concept of the electromagnetic field in physics. Faraday established that magnetism could affect rays of light and that there was an underlying relationship between the two phenomena, he discovered the principles of electromagnetic induction and diamagnetism, the laws of electrolysis. His inventions of electromagnetic rotary devices formed the foundation of electric motor technology, it was due to his efforts that electricity became practical for use in technology; as a chemist, Faraday discovered benzene, investigated the clathrate hydrate of chlorine, invented an early form of the Bunsen burner and the system of oxidation numbers, popularised terminology such as "anode", "cathode", "electrode" and "ion".
Faraday became the first and foremost Fullerian Professor of Chemistry at the Royal Institution, a lifetime position. Faraday was an excellent experimentalist who conveyed his ideas in simple language. James Clerk Maxwell took the work of Faraday and others and summarized it in a set of equations, accepted as the basis of all modern theories of electromagnetic phenomena. On Faraday's uses of lines of force, Maxwell wrote that they show Faraday "to have been in reality a mathematician of a high order – one from whom the mathematicians of the future may derive valuable and fertile methods." The SI unit of capacitance is named in his honour: the farad. Albert Einstein kept a picture of Faraday on his study wall, alongside pictures of Isaac Newton and James Clerk Maxwell. Physicist Ernest Rutherford stated, "When we consider the magnitude and extent of his discoveries and their influence on the progress of science and of industry, there is no honour too great to pay to the memory of Faraday, one of the greatest scientific discoverers of all time."
Michael Faraday was born on 22 September 1791 in Newington Butts, now part of the London Borough of Southwark but was a suburban part of Surrey. His family was not well off, his father, was a member of the Glassite sect of Christianity. James Faraday moved his wife and two children to London during the winter of 1790 from Outhgill in Westmorland, where he had been an apprentice to the village blacksmith. Michael was born in the autumn of that year; the young Michael Faraday, the third of four children, having only the most basic school education, had to educate himself. At the age of 14 he became an apprentice to George Riebau, a local bookbinder and bookseller in Blandford Street. During his seven-year apprenticeship Faraday read many books, including Isaac Watts's The Improvement of the Mind, he enthusiastically implemented the principles and suggestions contained therein, he developed an interest in science in electricity. Faraday was inspired by the book Conversations on Chemistry by Jane Marcet.
In 1812, at the age of 20 and at the end of his apprenticeship, Faraday attended lectures by the eminent English chemist Humphry Davy of the Royal Institution and the Royal Society, John Tatum, founder of the City Philosophical Society. Many of the tickets for these lectures were given to Faraday by William Dance, one of the founders of the Royal Philharmonic Society. Faraday subsequently sent Davy a 300-page book based on notes that he had taken during these lectures. Davy's reply was immediate and favourable. In 1813, when Davy damaged his eyesight in an accident with nitrogen trichloride, he decided to employ Faraday as an assistant. Coincidentally one of the Royal Institution's assistants, John Payne, was sacked and Sir Humphry Davy had been asked to find a replacement. Soon Davy entrusted Faraday with the preparation of nitrogen trichloride samples, they both were injured in an explosion of this sensitive substance. In the class-based English society of the time, Faraday was not considered a gentleman.
When Davy set out on a long tour of the continent in 1813–15, his valet did not wish to go, so instead, Faraday went as Davy's scientific assistant and was asked to act as Davy's valet until a replacement could be found in Paris. Faraday was forced to fill the role of valet as well as assistant throughout the trip. Davy's wife, Jane Apreece, refused to treat Faraday as an equal, made Faraday so miserable that he contemplated returning to England alone and giving up science altogether; the trip did, give him access to the scientific elite of Europe and exposed him to a host of stimulating ideas. Faraday married Sarah Barnard on 12 June 1821, they met through their families at the Sandemanian church, he confessed his faith to the Sandemanian congregation the month after they were married. They had no children. Faraday was a devout Christian. Well after his marriage, he served as deacon and for two terms as an elder in the meeting house of his youth, his church was located at Paul's Alley in the Barbican.
This meeting house relocated in 1862 to Islington.
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