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Electricity

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Electricity is the set of physical phenomena associated with the presence and motion of matter that has a property of electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by Maxwell's equations. Various common phenomena are related to electricity, including lightning, static electricity, electric heating, electric discharges and many others.

The presence of an electric charge, which can be either positive or negative, produces an electric field. The movement of electric charges is an electric current and produces a magnetic field.

When a charge is placed in a location with a non-zero electric field, a force will act on it. The magnitude of this force is given by Coulomb's law. If the charge moves, the electric field would be doing work on the electric charge. Thus we can speak of electric potential at a certain point in space, which is equal to the work done by an external agent in carrying a unit of positive charge from an arbitrarily chosen reference point to that point without any acceleration and is typically measured in volts.

Electricity is at the heart of many modern technologies, being used for:

  • Electric power where electric current is used to energise equipment;
  • Electronics which deals with electrical circuits that involve active electrical components such as vacuum tubes, transistors, diodes and integrated circuits, and associated passive interconnection technologies.

Electrical phenomena have been studied since antiquity, though progress in theoretical understanding remained slow until the seventeenth and eighteenth centuries. The theory of electromagnetism was developed in the 19th century, and by the end of that century electricity was being put to industrial and residential use by electrical engineers. The rapid expansion in electrical technology at this time transformed industry and society, becoming a driving force for the Second Industrial Revolution. Electricity's extraordinary versatility means it can be put to an almost limitless set of applications which include transport, heating, lighting, communications, and computation. Electrical power is now the backbone of modern industrial society.[1]

History[]

Main articles: History of electromagnetic theory and History of electrical engineering
See also: Etymology of electricity

Long before any knowledge of electricity existed, people were aware of shocks from electric fish. Ancient Egyptian texts dating from 2750 BCE referred to these fish as the "Thunderer of the Nile", and described them as the "protectors" of all other fish. Electric fish were again reported millennia later by ancient Greek, Roman and Arabic naturalists and physicians.[2] Several ancient writers, such as Pliny the Elder and Scribonius Largus, attested to the numbing effect of electric shocks delivered by electric catfish and electric rays, and knew that such shocks could travel along conducting objects.[3] Patients with ailments such as gout or headache were directed to touch electric fish in the hope that the powerful jolt might cure them.[4]

Ancient cultures around the Mediterranean knew that certain objects, such as rods of amber, could be rubbed with cat's fur to attract light objects like feathers. Phoenician philosopher Thales of Miletus made a series of observations on static electricity around 600 BCE, from which he believed that friction rendered amber magnetic, in contrast to minerals such as magnetite, which needed no rubbing.[5][6][7][8] Thales was incorrect in believing the attraction was due to a magnetic effect, but later science would prove a link between magnetism and electricity.

The ancient Parthians (150 BC to 223 AD) may have had knowledge of electroplating, based on the 1936 discovery of the Baghdad Battery, which resembles a galvanic cell.[9]

Abbas Ibn Firnas (810–887) invented an artificial weather simulation room, in which spectators saw stars and clouds, and were astonished by artificial thunder and lightning, which were produced by mechanisms hidden in his basement laboratory.[10][11] It is possible that some electricity may have been involved in producing the artificial thunder and lightning effects.

Electricity would remain little more than an intellectual curiosity for millennia until 1600, when the English scientist William Gilbert wrote De Magnete, in which he made a careful study of electricity and magnetism, distinguishing the lodestone effect from static electricity produced by rubbing amber.[5] He coined the New Latin word electricus ("of amber" or "like amber", from ἤλεκτρον, elektron, the Greek word for "amber") to refer to the property of attracting small objects after being rubbed.[12] This association gave rise to the English words "electric" and "electricity", which made their first appearance in print in Thomas Browne's Pseudodoxia Epidemica of 1646.[13]

Further work was conducted in the 17th and early 18th centuries by Otto von Guericke, Robert Boyle, Stephen Gray and C. F. du Fay.[14] Later in the 18th century, Benjamin Franklin conducted extensive research in electricity, selling his possessions to fund his work. In June 1752 he is reputed to have attached a metal key to the bottom of a dampened kite string and flown the kite in a storm-threatened sky.[15] A succession of sparks jumping from the key to the back of his hand showed that lightning was indeed electrical in nature.[16] He also explained the apparently paradoxical behavior[17] of the Leyden jar as a device for storing large amounts of electrical charge in terms of electricity consisting of both positive and negative charges.[14]

In 1775, Hugh Williamson reported a series of experiments to the Royal Society on the shocks delivered by the electric eel;[18] that same year the surgeon and anatomist John Hunter described the structure of the fish's electric organs.[19][20] In 1791, Luigi Galvani published his discovery of bioelectromagnetics, demonstrating that electricity was the medium by which neurons passed signals to the muscles.[21][22][14] Alessandro Volta's battery, or voltaic pile, of 1800, made from alternating layers of zinc and copper, provided scientists with a more reliable source of electrical energy than the electrostatic machines previously used.[21][22] The recognition of electromagnetism, the unity of electric and magnetic phenomena, is due to Hans Christian Ørsted and André-Marie Ampère in 1819–1820. Michael Faraday invented the electric motor in 1821, and Georg Ohm mathematically analysed the electrical circuit in 1827.[22] Electricity and magnetism (and light) were definitively linked by James Clerk Maxwell, in particular in his "On Physical Lines of Force" in 1861 and 1862.[23]

While the early 19th century had seen rapid progress in electrical science, the late 19th century would see the greatest progress in electrical engineering. Through such people as Alexander Graham Bell, Ottó Bláthy, Thomas Edison, Galileo Ferraris, Oliver Heaviside, Ányos Jedlik, William Thomson, 1st Baron Kelvin, Charles Algernon Parsons, Werner von Siemens, Joseph Swan, Reginald Fessenden, Nikola Tesla and George Westinghouse, electricity turned from a scientific curiosity into an essential tool for modern life.

In 1887, Heinrich Hertz[24]:843–44[25] discovered that electrodes illuminated with ultraviolet light create electric sparks more easily. In 1905, Albert Einstein published a paper that explained experimental data from the photoelectric effect as being the result of light energy being carried in discrete quantized packets, energising electrons. This discovery led to the quantum revolution. Einstein was awarded the Nobel Prize in Physics in 1921 for "his discovery of the law of the photoelectric effect".[26] The photoelectric effect is also employed in photocells such as can be found in solar panels and this is frequently used to make electricity commercially.

The first solid-state device was the "cat's-whisker detector" first used in the 1900s in radio receivers. A whisker-like wire is placed lightly in contact with a solid crystal (such as a germanium crystal) to detect a radio signal by the contact junction effect.[27] In a solid-state component, the current is confined to solid elements and compounds engineered specifically to switch and amplify it. Current flow can be understood in two forms: as negatively charged electrons, and as positively charged electron deficiencies called holes. These charges and holes are understood in terms of quantum physics. The building material is most often a crystalline semiconductor.[28][29]

Solid-state electronics came into its own with the emergence of transistor technology. The first working transistor, a germanium-based point-contact transistor, was invented by John Bardeen and Walter Houser Brattain at Bell Labs in 1947,[30] followed by the bipolar junction transistor in 1948.[31] These early transistors were relatively bulky devices that were difficult to manufacture on a mass-production basis.[32]:168 They were followed by the silicon-based MOSFET (metal-oxide-semiconductor field-effect transistor, or MOS transistor), invented by Mohamed M. Atalla and Dawon Kahng at Bell Labs in 1959.[33][34][35] It was the first truly compact transistor that could be miniaturised and mass-produced for a wide range of uses, leading to the silicon revolution.[36] Solid-state devices started becoming prevalent from the 1960s, with the transition from vacuum tubes to semiconductor diodes, transistors, integrated circuit (IC) chips, MOSFETs, and light-emitting diode (LED) technology.

The most common electronic device is the MOSFET,[34][37] which has become the most widely manufactured device in history.[38] Common solid-state MOS devices include microprocessor chips[39] and semiconductor memory.[40][41] A special type of semiconductor memory is flash memory, which is used in USB flash drives and mobile devices, as well as solid-state drive (SSD) technology to replace mechanically rotating magnetic disc hard disk drive (HDD) technology.

Concepts[]

Electric potential[]

Main article: Electric potential
See also: Voltage and Battery (electricity)

The concept of electric potential is closely linked to that of the electric field. A small charge placed within an electric field experiences a force, and to have brought that charge to that point against the force requires work. The electric potential at any point is defined as the energy required to bring a unit test charge from an infinite distance slowly to that point. It is usually measured in volts, and one volt is the potential for which one joule of work must be expended to bring a charge of one coulomb from infinity.[24]:494–98 This definition of potential, while formal, has little practical application, and a more useful concept is that of electric potential difference, and is the energy required to move a unit charge between two specified points. An electric field has the special property that it is conservative, which means that the path taken by the test charge is irrelevant: all paths between two specified points expend the same energy, and thus a unique value for potential difference may be stated.[24]:494–98 The volt is so strongly identified as the unit of choice for measurement and description of electric potential difference that the term voltage sees greater everyday usage.

For practical purposes, it is useful to define a common reference point to which potentials may be expressed and compared. While this could be at infinity, a much more useful reference is the Earth itself, which is assumed to be at the same potential everywhere. This reference point naturally takes the name earth or ground. Earth is assumed to be an infinite source of equal amounts of positive and negative charge, and is therefore electrically uncharged—and unchargeable.[42]

Electric potential is a scalar quantity, that is, it has only magnitude and not direction. It may be viewed as analogous to height: just as a released object will fall through a difference in heights caused by a gravitational field, so a charge will 'fall' across the voltage caused by an electric field.[43] As relief maps show contour lines marking points of equal height, a set of lines marking points of equal potential (known as equipotentials) may be drawn around an electrostatically charged object. The equipotentials cross all lines of force at right angles. They must also lie parallel to a conductor's surface, otherwise this would produce a force that will move the charge carriers to even the potential of the surface.

The electric field was formally defined as the force exerted per unit charge, but the concept of potential allows for a more useful and equivalent definition: the electric field is the local gradient of the electric potential. Usually expressed in volts per metre, the vector direction of the field is the line of greatest slope of potential, and where the equipotentials lie closest together.[44]:60

Electrochemistry[]

Main article: Electrochemistry

The ability of chemical reactions to produce electricity, and conversely the ability of electricity to drive chemical reactions has a wide array of uses.

Electrochemistry has always been an important part of electricity. From the initial invention of the Voltaic pile, electrochemical cells have evolved into the many different types of batteries, electroplating and electrolysis cells. Aluminium is produced in vast quantities this way, and many portable devices are electrically powered using rechargeable cells.

Electric circuits[]

Main article: Electric circuit

An electric circuit is an interconnection of electric components such that electric charge is made to flow along a closed path (a circuit), usually to perform some useful task.

The components in an electric circuit can take many forms, which can include elements such as resistors, capacitors, switches, transformers and electronics. Electronic circuits contain active components, usually semiconductors, and typically exhibit non-linear behaviour, requiring complex analysis. The simplest electric components are those that are termed passive and linear: while they may temporarily store energy, they contain no sources of it, and exhibit linear responses to stimuli.[45]:15–16

The resistor is perhaps the simplest of passive circuit elements: as its name suggests, it resists the current through it, dissipating its energy as heat. The resistance is a consequence of the motion of charge through a conductor: in metals, for example, resistance is primarily due to collisions between electrons and ions. Ohm's law is a basic law of circuit theory, stating that the current passing through a resistance is directly proportional to the potential difference across it. The resistance of most materials is relatively constant over a range of temperatures and currents; materials under these conditions are known as 'ohmic'. The ohm, the unit of resistance, was named in honour of Georg Ohm, and is symbolised by the Greek letter Ω. 1 Ω is the resistance that will produce a potential difference of one volt in response to a current of one amp.[45]:30–35

The capacitor is a development of the Leyden jar and is a device that can store charge, and thereby storing electrical energy in the resulting field. It consists of two conducting plates separated by a thin insulating dielectric layer; in practice, thin metal foils are coiled together, increasing the surface area per unit volume and therefore the capacitance. The unit of capacitance is the farad, named after Michael Faraday, and given the symbol F: one farad is the capacitance that develops a potential difference of one volt when it stores a charge of one coulomb. A capacitor connected to a voltage supply initially causes a current as it accumulates charge; this current will however decay in time as the capacitor fills, eventually falling to zero. A capacitor will therefore not permit a steady state current, but instead blocks it.[45]:216–20

The inductor is a conductor, usually a coil of wire, that stores energy in a magnetic field in response to the current through it. When the current changes, the magnetic field does too, inducing a voltage between the ends of the conductor. The induced voltage is proportional to the time rate of change of the current. The constant of proportionality is termed the inductance. The unit of inductance is the henry, named after Joseph Henry, a contemporary of Faraday. One henry is the inductance that will induce a potential difference of one volt if the current through it changes at a rate of one ampere per second. The inductor's behaviour is in some regards converse to that of the capacitor: it will freely allow an unchanging current, but opposes a rapidly changing one.[45]:226–29

Electric power[]

Main article: electric power

Electric power is the rate at which electric energy is transferred by an electric circuit. The SI unit of power is the watt, one joule per second.

Electric power, like mechanical power, is the rate of doing work, measured in watts, and represented by the letter P. The term wattage is used colloquially to mean "electric power in watts." The electric power in watts produced by an electric current I consisting of a charge of Q coulombs every t seconds passing through an electric potential (voltage) difference of V is

where

Q is electric charge in coulombs
t is time in seconds
I is electric current in amperes
V is electric potential or voltage in volts

Electricity generation is often done by a process of converting mechanical energy to electricity. Devices such as steam turbines or gas turbines are involved in the production of the mechanical energy, which is passed on to electric generators which produce the electricity. Electricity can also be supplied by chemical sources such as electric batteries or by other means from a wide variety of sources of energy. Electric power is generally supplied to businesses and homes by the electric power industry. Electricity is usually sold by the kilowatt hour (3.6 MJ) which is the product of power in kilowatts multiplied by running time in hours. Electric utilities measure power using electricity meters, which keep a running total of the electric energy delivered to a customer. Unlike fossil fuels, electricity is a low entropy form of energy and can be converted into motion or many other forms of energy with high efficiency.[46]

Electronics[]

Main article: electronics

Electronics deals with electrical circuits that involve active electrical components such as vacuum tubes, transistors, diodes, optoelectronics, sensors and integrated circuits, and associated passive interconnection technologies. The nonlinear behaviour of active components and their ability to control electron flows makes amplification of weak signals possible and electronics is widely used in information processing, telecommunications, and signal processing. The ability of electronic devices to act as switches makes digital information processing possible. Interconnection technologies such as circuit boards, electronics packaging technology, and other varied forms of communication infrastructure complete circuit functionality and transform the mixed components into a regular working system.

Today, most electronic devices use semiconductor components to perform electron control. The study of semiconductor devices and related technology is considered a branch of solid state physics, whereas the design and construction of electronic circuits to solve practical problems come under electronics engineering.

Notes[]

  1. ↑ Jones, D.A. (1991), "Electrical engineering: the backbone of society", IEE Proceedings A - Science, Measurement and Technology, 138 (1): 1–10, doi:10.1049/ip-a-3.1991.0001
  2. ↑ Moller, Peter; Kramer, Bernd (December 1991), "Review: Electric Fish", BioScience, American Institute of Biological Sciences, 41 (11): 794–96 [794], doi:10.2307/1311732, JSTOR 1311732
  3. ↑ Bullock, Theodore H. (2005), Electroreception, Springer, pp. 5–7, ISBN 0-387-23192-7
  4. ↑ Morris, Simon C. (2003), Life's Solution: Inevitable Humans in a Lonely Universe, Cambridge University Press, pp. 182–85, ISBN 0-521-82704-3
  5. ↑ 5.0 5.1 Stewart, Joseph (2001), Intermediate Electromagnetic Theory, World Scientific, p. 50, ISBN 981-02-4471-1
  6. ↑ Simpson, Brian (2003), Electrical Stimulation and the Relief of Pain, Elsevier Health Sciences, pp. 6–7, ISBN 0-444-51258-6
  7. ↑ Diogenes Laertius. R.D. Hicks (ed.). "Lives of Eminent Philosophers, Book 1 Chapter 1 [24]". Perseus Digital Library. Tufts University. Archived from the original on 30 July 2022. Retrieved 5 February 2017. Aristotle and Hippias affirm that, arguing from the magnet and from amber, he attributed a soul or life even to inanimate objects.
  8. ↑ Aristotle. Daniel C. Stevenson (ed.). "De Animus (On the Soul) Book 1 Part 2 (B4 verso)". The Internet Classics Archive. Translated by J.A. Smith. Archived from the original on 26 February 2017. Retrieved 5 February 2017. Thales, too, to judge from what is recorded about him, seems to have held soul to be a motive force, since he said that the magnet has a soul in it because it moves the iron.
  9. ↑ Frood, Arran (27 February 2003), Riddle of 'Baghdad's batteries', BBC, archived from the original on 2017-09-03, retrieved 2008-02-16
  10. ↑ Lynn Townsend White, Jr. (Spring, 1961). "Eilmer of Malmesbury, an Eleventh Century Aviator: A Case Study of Technological Innovation, Its Context and Tradition", Technology and Culture 2 (2), p. 97-111 [100-1]
  11. ↑ Imamuddin, S. M. (1981), Muslim Spain 711-1492 A.D., Brill Publishers, p. 166, ISBN 9004061312
  12. ↑ Baigrie, Brian (2007), Electricity and Magnetism: A Historical Perspective, Greenwood Press, pp. 7–8, ISBN 978-0-313-33358-3
  13. ↑ Chalmers, Gordon (1937), "The Lodestone and the Understanding of Matter in Seventeenth Century England", Philosophy of Science, 4 (1): 75–95, doi:10.1086/286445, S2CID 121067746
  14. ↑ 14.0 14.1 14.2 Guarnieri, M. (2014). "Electricity in the age of Enlightenment". IEEE Industrial Electronics Magazine. 8 (3): 60–63. doi:10.1109/MIE.2014.2335431. S2CID 34246664.
  15. ↑ Srodes, James (2002), Franklin: The Essential Founding Father, Regnery Publishing, pp. 92–94, ISBN 0-89526-163-4 It is uncertain if Franklin personally carried out this experiment, but it is popularly attributed to him.
  16. ↑ Uman, Martin (1987), All About Lightning (PDF), Dover Publications, ISBN 0-486-25237-X
  17. ↑ Riskin, Jessica (1998), Poor Richard's Leyden Jar: Electricity and economy in Franklinist France (PDF), p. 327, archived (PDF) from the original on 2014-05-12, retrieved 2014-05-11
  18. ↑ Williamson, Hugh (1775). "Experiments and observations on the Gymnotus electricus, or electric eel". Philosophical Transactions of the Royal Society. 65 (65): 94–101. doi:10.1098/rstl.1775.0011. S2CID 186211272. Archived from the original on 2022-07-30. Retrieved 2022-07-16.
  19. ↑ Edwards, Paul J. (2021). "A Correction to the Record of Early Electrophysiology Research on the 250th Anniversary of a Historic Expedition to Île de Ré."
  20. ↑ Hunter, John (1775). "An account of the Gymnotus electricus". Philosophical Transactions of the Royal Society of London (65): 395–407.
  21. ↑ 21.0 21.1 Guarnieri, M. (2014). "The Big Jump from the Legs of a Frog". IEEE Industrial Electronics Magazine. 8 (4): 59–61, 69. doi:10.1109/MIE.2014.2361237. S2CID 39105914.
  22. ↑ 22.0 22.1 22.2 Kirby, Richard S. (1990), Engineering in History, Courier Dover Publications, pp. 331–33, ISBN 0-486-26412-2
  23. ↑ Berkson, William (1974) Fields of force: the development of a world view from Faraday to Einstein p.148. Routledge, 1974
  24. ↑ 24.0 24.1 24.2 Sears, Francis; et al. (1982), University Physics, Sixth Edition, Addison Wesley, ISBN 0-201-07199-1
  25. ↑ Hertz, Heinrich (1887). "Ueber den Einfluss des ultravioletten Lichtes auf die electrische Entladung". Annalen der Physik. 267 (8): S. 983–1000. Bibcode:1887AnP...267..983H. doi:10.1002/andp.18872670827. Archived from the original on 2020-06-11. Retrieved 2019-08-25.
  26. ↑ "The Nobel Prize in Physics 1921". Nobel Foundation. Archived from the original on 2008-10-17. Retrieved 2013-03-16.
  27. ↑ "Solid state" Archived 2018-07-21 at the Wayback Machine, The Free Dictionary
  28. ↑ John Sydney Blakemore, Solid state physics, pp. 1–3, Cambridge University Press, 1985 ISBN 0-521-31391-0.
  29. ↑ Richard C. Jaeger, Travis N. Blalock, Microelectronic circuit design, pp. 46–47, McGraw-Hill Professional, 2003 ISBN 0-07-250503-6.
  30. ↑ "1947: Invention of the Point-Contact Transistor". Computer History Museum. Archived from the original on 30 September 2021. Retrieved 10 August 2019.
  31. ↑ "1948: Conception of the Junction Transistor". The Silicon Engine. Computer History Museum. Archived from the original on 30 July 2020. Retrieved 8 October 2019.
  32. ↑ Moskowitz, Sanford L. (2016). Advanced Materials Innovation: Managing Global Technology in the 21st century. John Wiley & Sons. ISBN 9780470508923. Archived from the original on 2020-11-05. Retrieved 2019-10-26.
  33. ↑ "1960 - Metal Oxide Semiconductor (MOS) Transistor Demonstrated". The Silicon Engine. Computer History Museum. Archived from the original on 2019-10-27. Retrieved 2019-10-26.
  34. ↑ 34.0 34.1 "Who Invented the Transistor?". Computer History Museum. 4 December 2013. Archived from the original on 13 December 2013. Retrieved 20 July 2019.
  35. ↑ "Triumph of the MOS Transistor". YouTube. Computer History Museum. 6 August 2010. Archived from the original on 2021-10-28. Retrieved 21 July 2019.
  36. ↑ Feldman, Leonard C. (2001). "Introduction". Fundamental Aspects of Silicon Oxidation. Springer Science & Business Media. pp. 1–11. ISBN 9783540416821. Archived from the original on 2019-12-25. Retrieved 2019-10-26.
  37. ↑ Golio, Mike; Golio, Janet (2018). RF and Microwave Passive and Active Technologies. CRC Press. pp. 18–2. ISBN 9781420006728. Archived from the original on 2020-11-04. Retrieved 2019-10-26.
  38. ↑ "13 Sextillion & Counting: The Long & Winding Road to the Most Frequently Manufactured Human Artifact in History". Computer History Museum. April 2, 2018. Archived from the original on 28 July 2019. Retrieved 28 July 2019.
  39. ↑ Shirriff, Ken (30 August 2016). "The Surprising Story of the First Microprocessors". IEEE Spectrum. Institute of Electrical and Electronics Engineers. 53 (9): 48–54. doi:10.1109/MSPEC.2016.7551353. S2CID 32003640. Archived from the original on 12 July 2021. Retrieved 13 October 2019.
  40. ↑ "The MOS Memory Market" (PDF). Integrated Circuit Engineering Corporation. Smithsonian Institution. 1997. Archived (PDF) from the original on 26 June 2011. Retrieved 16 October 2019.
  41. ↑ "MOS Memory Market Trends" (PDF). Integrated Circuit Engineering Corporation. Smithsonian Institution. 1998. Archived (PDF) from the original on 16 October 2019. Retrieved 16 October 2019.
  42. ↑ Serway, Raymond A. (2006), Serway's College Physics, Thomson Brooks, p. 500, ISBN 0-534-99724-4
  43. ↑ Saeli, Sue; MacIsaac, Dan (2007), "Using Gravitational Analogies To Introduce Elementary Electrical Field Theory Concepts", The Physics Teacher, 45 (2): 104, Bibcode:2007PhTea..45..104S, doi:10.1119/1.2432088, archived from the original on 2008-02-16, retrieved 2007-12-09
  44. ↑ Duffin, W.J. (1980), Electricity and Magnetism, 3rd edition, McGraw-Hill, ISBN 0-07-084111-X
  45. ↑ 45.0 45.1 45.2 45.3 Alexander, Charles; Sadiku, Matthew (2006), Fundamentals of Electric Circuits (3, revised ed.), McGraw-Hill, ISBN 9780073301150
  46. ↑ Environmental Physics By Clare Smith 2001

References[]

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