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Electromagnetism
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{{Short description|Fundamental interaction between charged particles}}{{Pp-semi-indef}}{{Redirect|Electromagnetics|the academic journal|Electromagnetics (journal){{!}}Electromagnetics (journal)}}{{Redirect|Electromagnetic force|the force exerted on particles by electromagnetic fields|Lorentz force}}{{For introduction}}{{Redirect-synonym|Electromagnetic|the use of an electromagnet}}File:Plasma globe 60th.jpg|thumb|300x300px|Electromagnetic interactions are responsible for the glowing filaments in this plasma globeplasma globe{{Electromagnetism|cTopic=-}}In physics, electromagnetism is an interaction that occurs between particles with electric charge via electromagnetic fields. The electromagnetic force is one of the four fundamental forces of nature. It is the dominant force in the interactions of atoms and molecules. Electromagnetism can be thought of as a combination of electrostatics and magnetism, which are distinct but closely intertwined phenomena. Electromagnetic forces occur between any two charged particles. Electric forces cause an attraction between particles with opposite charges and repulsion between particles with the same charge, while magnetism is an interaction that occurs between charged particles in relative motion. These two forces are described in terms of electromagnetic fields. Macroscopic charged objects are described in terms of Coulomb's law for electricity and Ampère's force law for magnetism; the Lorentz force describes microscopic charged particles.The electromagnetic force is responsible for many of the chemical and physical phenomena observed in daily life. The electrostatic attraction between atomic nuclei and their electrons holds atoms together. Electric forces also allow different atoms to combine into molecules, including the macromolecules such as proteins that form the basis of life. Meanwhile, magnetic interactions between the spin and angular momentum magnetic moments of electrons also play a role in chemical reactivity; such relationships are studied in spin chemistry. Electromagnetism also plays several crucial roles in modern technology: electrical energy production, transformation and distribution; light, heat, and sound production and detection; fiber optic and wireless communication; sensors; computation; electrolysis; electroplating; and mechanical motors and actuators.Electromagnetism has been studied since ancient times. Many ancient civilizations, including the Greeks and the Mayans, created wide-ranging theories to explain lightning, static electricity, and the attraction between magnetized pieces of iron ore. However, it was not until the late 18th century that scientists began to develop a mathematical basis for understanding the nature of electromagnetic interactions. In the 18th and 19th centuries, prominent scientists and mathematicians such as Coulomb, Gauss and Faraday developed namesake laws which helped to explain the formation and interaction of electromagnetic fields. This process culminated in the 1860s with the discovery of Maxwell's equations, a set of four partial differential equations which provide a complete description of classical electromagnetic fields. Maxwell's equations provided a sound mathematical basis for the relationships between electricity and magnetism that scientists had been exploring for centuries, and predicted the existence of self-sustaining electromagnetic waves. Maxwell postulated that such waves make up visible light, which was later shown to be true. Gamma-rays, x-rays, ultraviolet, visible, infrared radiation, microwaves and radio waves were all determined to be electromagnetic radiation differing only in their range of frequencies.In the modern era, scientists have continued to refine the theorem of electromagnetism to take into account the effects of modern physics, including quantum mechanics and relativity. The theoretical implications of electromagnetism, particularly the establishment of the speed of light based on properties of the "medium" of propagation (permeability and permittivity), helped inspire Einstein's theory of special relativity in 1905. Meanwhile, the field of quantum electrodynamics (QED) has modified Maxwell's equations to be consistent with the quantized nature of matter. In QED, the changes in the electromagnetic field is expressed in terms of discrete excitations, particles known as photons, the quanta of light.- the content below is remote from Wikipedia
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History
Ancient world
Investigation into electromagnetic phenomena began about 5,000 years ago. There is evidence that the ancient Chinese,BOOK, Meyer, Herbert, A History of Electricity and Magnetism, 1972, 2, en, Mayan,WEB, Magazine, Smithsonian, Learn, Joshua Rapp, Mesoamerican Sculptures Reveal Early Knowledge of Magnetism,weblink 2022-12-07, Smithsonian Magazine, en, and potentially even Egyptian civilizations knew that the naturally magnetic mineral magnetite had attractive properties, and many incorporated it into their art and architecture.{{Citation |last1=du Trémolet de Lacheisserie |first1=Ã. |title=Magnetism, from the Dawn of Civilization to Today |date=2002 |url=https://doi.org/10.1007/978-0-387-23062-7_1 |work=Magnetism |pages=3â18 |editor-last=du Trémolet de Lacheisserie |editor-first=Ã. |place=New York, NY |publisher=Springer |language=en |doi=10.1007/978-0-387-23062-7_1 |isbn=978-0-387-23062-7 |access-date=2022-12-07 |last2=Gignoux |first2=D. |last3=Schlenker |first3=M. |editor2-last=Gignoux |editor2-first=D. |editor3-last=Schlenker |editor3-first=M.}} Ancient people were also aware of lightning and static electricity, although they had no idea of the mechanisms behind these phenomena. The Greek philosopher Thales of Miletus discovered around 600 B.C.E. that amber could acquire an electric charge when it was rubbed with cloth, which allowed it to pick up light objects such as pieces of straw. Thales also experimented with the ability of magnetic rocks to attract one other, and hypothesized that this phenomenon might be connected to the attractive power of amber, foreshadowing the deep connections between electricity and magnetism that would be discovered over 2,000 years later. Despite all this investigation, ancient civilizations had no understanding of the mathematical basis of electromagnetism, and often analyzed its impacts through the lens of religion rather than science (lightning, for instance, was considered to be a creation of the gods in many cultures).BOOK, Meyer, Herbert, A History of Electricity and Magnetism, 1972, 3â4, en,19th century
(File:A Treatise on Electricity and Magnetism Volume 2 003.jpg|thumb|Cover of A Treatise on Electricity and Magnetism)Electricity and magnetism were originally considered to be two separate forces. This view changed with the publication of James Clerk Maxwell's 1873 A Treatise on Electricity and MagnetismJOURNAL, 24 April 1873, A Treatise on Electricity and Magnetism,weblink Nature, en, 7, 182, 478â480, 10.1038/007478a0, 1873Natur...7..478., 10178476, 0028-0836, in which the interactions of positive and negative charges were shown to be mediated by one force. There are four main effects resulting from these interactions, all of which have been clearly demonstrated by experiments:- Electric charges {{vanchor|attract}} or {{vanchor|repel}} one another with a force inversely proportional to the square of the distance between them: unlike charges attract, like ones repel.WEB, 2019-02-06, Why Do Like Charges Repel And Opposite Charges Attract?,weblink 2022-08-22, Science ABC, en-US,
- Magnetic poles (or states of polarization at individual points) attract or repel one another in a manner similar to positive and negative charges and always exist as pairs: every north pole is yoked to a south pole.WEB, What Makes Magnets Repel?,weblink 2022-08-22, Sciencing, en,
- An electric current inside a wire creates a corresponding circumferential magnetic field outside the wire. Its direction (clockwise or counter-clockwise) depends on the direction of the current in the wire.WEB, Jim Lucas Contributions from Ashley Hamer, 2022-02-18, What Is Faraday's Law of Induction?,weblink 2022-08-22, livescience.com, en,
- A current is induced in a loop of wire when it is moved toward or away from a magnetic field, or a magnet is moved towards or away from it; the direction of current depends on that of the movement.
A fundamental force
(File:Circular.Polarization.Circularly.Polarized.Light Right.Handed.Animation.305x190.255Colors.gif|thumb|right|220px|Representation of the electric field vector of a wave of circularly polarized electromagnetic radiation)The electromagnetic force is the second strongest of the four known fundamental forces. It operates with infinite range.WEB, Rehm, Jeremy, published, Ben Biggs, 2021-12-23, The four fundamental forces of nature,weblink 2022-08-22, Space.com, en, All other forces (e.g., friction, contact forces) are derived from these four fundamental forces and they are known as non-fundamental forces.Browne, "Physics for Engineering and Science", p. 160: "Gravity is one of the fundamental forces of nature. The other forces such as friction, tension, and the normal force are derived from the electric force, another of the fundamental forces. Gravity is a rather weak force... The electric force between two protons is much stronger than the gravitational force between them."At high energy, the weak force and electromagnetic force are unified as a single interaction called the electroweak interaction.JOURNAL, Salam, A., Ward, J.C., November 1964, Electromagnetic and weak interactions,weblink Physics Letters, en, 13, 2, 168â171, 10.1016/0031-9163(64)90711-5, Roughly speaking, all the forces involved in interactions between atoms can be explained by the electromagnetic force acting between the electrically charged atomic nuclei and electrons of the atoms. Electromagnetic forces also explain how these particles carry momentum by their movement. This includes the forces we experience in "pushing" or "pulling" ordinary material objects, which result from the intermolecular forces that act between the individual molecules in our bodies and those in the objects. The electromagnetic force is also involved in all forms of chemical phenomena.A necessary part of understanding the intra-atomic and intermolecular forces is the effective force generated by the momentum of the electrons' movement, such that as electrons move between interacting atoms they carry momentum with them. As a collection of electrons becomes more confined, their minimum momentum necessarily increases due to the Pauli exclusion principle. The behaviour of matter at the molecular scale including its density is determined by the balance between the electromagnetic force and the force generated by the exchange of momentum carried by the electrons themselves.Purcell, "Electricity and Magnetism, 3rd Edition", p. 546: Ch 11 Section 6, "Electron Spin and Magnetic Moment."Classical electrodynamics
In 1600, William Gilbert proposed, in his De Magnete, that electricity and magnetism, while both capable of causing attraction and repulsion of objects, were distinct effects.JOURNAL, Malin, Stuart, Barraclough, David, 2000, Gilbert's De Magnete: An early study of magnetism and electricity,weblink Eos, Transactions American Geophysical Union, en, 81, 21, 233, 10.1029/00EO00163, 2000EOSTr..81..233M, 0096-3941, Mariners had noticed that lightning strikes had the ability to disturb a compass needle. The link between lightning and electricity was not confirmed until Benjamin Franklin's proposed experiments in 1752 were conducted on 10{{nbsp}}May 1752 by Thomas-François Dalibard of France using a {{convert|40|ft|m|adj=mid|-tall}} iron rod instead of a kite and he successfully extracted electrical sparks from a cloud.WEB,weblink Lightning! | Museum of Science, Boston, BOOK, Tucker, Tom,weblink Bolt of fate : Benjamin Franklin and his electric kite hoax, 2003, PublicAffairs, 1-891620-70-3, 1st, New York, 51763922, One of the first to discover and publish a link between human-made electric current and magnetism was Gian Romagnosi, who in 1802 noticed that connecting a wire across a voltaic pile deflected a nearby compass needle. However, the effect did not become widely known until 1820, when Ãrsted performed a similar experiment.WEB,weblink Magnetic Fields â History, 2009-11-27, Stern, Dr. David P., Mauricio, Peredo, 2001-11-25, NASA Goddard Space Flight Center, Ãrsted's work influenced Ampère to conduct further experiments, which eventually gave rise to a new area of physics: electrodynamics. By determining a force law for the interaction between elements of electric current, Ampère placed the subject on a solid mathematical foundation.WEB, 2016-01-13, Andre-Marie Ampère,weblink 2022-08-22, ETHW, en, A theory of electromagnetism, known as classical electromagnetism, was developed by several physicists during the period between 1820 and 1873, when James Clerk Maxwell's treatise was published, which unified previous developments into a single theory, proposing that light was an electromagnetic wave propagating in the luminiferous ether.Purcell, p. 436. Chapter 9.3, "Maxwell's description of the electromagnetic field was essentially complete." In classical electromagnetism, the behavior of the electromagnetic field is described by a set of equations known as Maxwell's equations, and the electromagnetic force is given by the Lorentz force law.Purcell: p. 278: Chapter 6.1, "Definition of the Magnetic Field." Lorentz force and force equation.One of the peculiarities of classical electromagnetism is that it is difficult to reconcile with classical mechanics, but it is compatible with special relativity. According to Maxwell's equations, the speed of light in vacuum is a universal constant that is dependent only on the electrical permittivity and magnetic permeability of free space. This violates Galilean invariance, a long-standing cornerstone of classical mechanics. One way to reconcile the two theories (electromagnetism and classical mechanics) is to assume the existence of a luminiferous aether through which the light propagates. However, subsequent experimental efforts failed to detect the presence of the aether. After important contributions of Hendrik Lorentz and Henri Poincaré, in 1905, Albert Einstein solved the problem with the introduction of special relativity, which replaced classical kinematics with a new theory of kinematics compatible with classical electromagnetism. (For more information, see History of special relativity.)In addition, relativity theory implies that in moving frames of reference, a magnetic field transforms to a field with a nonzero electric component and conversely, a moving electric field transforms to a nonzero magnetic component, thus firmly showing that the phenomena are two sides of the same coin. Hence the term "electromagnetism". (For more information, see Classical electromagnetism and special relativity and Covariant formulation of classical electromagnetism.)Today few problems in electromagnetism remain unsolved. These include: the lack of magnetic monopoles, AbrahamâMinkowski controversy, and the mechanism by which some organisms can sense electric and magnetic fields.Extension to nonlinear phenomena
The Maxwell equations are linear, in that a change in the sources (the charges and currents) results in a proportional change of the fields. Nonlinear dynamics can occur when electromagnetic fields couple to matter that follows nonlinear dynamical laws.JOURNAL, Jufriansah, Adi, Hermanto, Arief, Toifur, Moh., Prasetyo, Erwin, 2020-05-18, Theoretical study of Maxwell's equations in nonlinear optics, AIP Conference Proceedings, 2234, 1, 040013, 10.1063/5.0008179, 2020AIPC.2234d0013J, 219451710, 0094-243X, free, This is studied, for example, in the subject of magnetohydrodynamics, which combines Maxwell theory with the NavierâStokes equations.THESIS, Some aspects of magnetohydrodynamics,weblink University of Cambridge, 1967-07-27, Thesis, 10.17863/cam.14141, en, Julian C. R., Hunt, Another branch of electromagnetism dealing with nonlinearity is nonlinear optics.Quantities and units
{{see also|List of physical quantities|List of electromagnetism equations}}Here is a list of common units related to electromagnetism:WEB, Essentials of the SI: Base & derived units,weblink 2022-08-22, physics.nist.gov, {{Div col}}- ampere (electric current)
- coulomb (electric charge)
- farad (capacitance)
- henry (inductance)
- ohm (resistance)
- siemens (conductance)
- tesla (magnetic flux density)
- volt (electric potential)
- watt (power)
- weber (magnetic flux)
Applications
The study of electromagnetism informs electric circuits, magnetic circuits, and semiconductor devices' construction.See also
{{Div col|colwidth=25em}}- AbrahamâLorentz force
- Aeromagnetic surveys
- Computational electromagnetics
- Double-slit experiment
- Electrodynamic droplet deformation
- Electromagnet
- Electromagnetic induction
- Electromagnetic wave equation
- Electromagnetic scattering
- Electromechanics
- Geophysics
- Introduction to electromagnetism
- Magnetostatics
- Magnetoquasistatic field
- Optics
- Relativistic electromagnetism
- WheelerâFeynman absorber theory
References
{{reflist}}Further reading
{{Library resources box|by=no|onlinebooks=no|others=no|about=yes|label=Electromagnetism}}Web sources
- WEB
- WEB
Textbooks
- BOOK, Electricity and Modern Physics, 2nd, G.A.G. Bennet, Edward Arnold (UK), 1974, 978-0-7131-2459-0,
- BOOK, Browne, Michael, Physics for Engineering and Science, 2nd, McGraw-Hill/Schaum, 2008, 978-0-07-161399-6,
- BOOK, Dibner, Bern, Oersted and the discovery of electromagnetism, Literary Licensing, LLC, 2012, 978-1-258-33555-7,
- BOOK, Durney, Carl H., Johnson, Curtis C., Introduction to modern electromagnetics, McGraw-Hill, 1969, 978-0-07-018388-9,
- BOOK, Feynman, Richard P., The Feynman Lectures on Physics Vol II, Addison Wesley Longman, 1970, 978-0-201-02115-8,weblink
- BOOK, Fleisch, Daniel, A Student's Guide to Maxwell's Equations, 2008, Cambridge University Press, Cambridge, UK, 978-0-521-70147-1,
- BOOK, Electromagnetism,weblink registration, 2nd, I.S. Grant, W.R. Phillips, Manchester Physics, John Wiley & Sons, 2008, 978-0-471-92712-9,
- BOOK, Griffiths, David J., Introduction to Electrodynamics, 3rd, Prentice Hall, 1998, 978-0-13-805326-0, David J. Griffiths,weblink
- BOOK, Jackson, John D., Classical Electrodynamics,weblink registration, John David Jackson (physicist), 3rd, Wiley, 1998, 978-0-471-30932-1,
- BOOK, Moliton, André, Basic electromagnetism and materials, Springer-Verlag New York, 2007, New York,weblink 978-0-387-30284-3,
- BOOK, Purcell, Edward M., Edward Mills Purcell, Electricity and Magnetism Berkeley, Physics Course Volume 2 (2nd ed.), McGraw-Hill, 1985, 978-0-07-004908-6,
- BOOK, Purcell, Edward M and Morin, David., Electricity and Magnetism, 820p, 3rd, Cambridge University Press, New York., 2013, 978-1-107-01402-2,
- BOOK, Rao, Nannapaneni N., Elements of engineering electromagnetics (4th ed.), Prentice Hall, 1994, 978-0-13-948746-0,
- BOOK, Rothwell, Edward J., Cloud, Michael J., Electromagnetics, CRC Press, 2001, 978-0-8493-1397-4,
- BOOK, Tipler, Paul, Physics for Scientists and Engineers: Vol. 2: Light, Electricity and Magnetism, 4th, W.H. Freeman, 1998, 978-1-57259-492-0,
- BOOK, Wangsness, Roald K., Cloud, Michael J., Electromagnetic Fields, Wiley, 1986, 978-0-471-81186-2, 2nd,
General coverage
- BOOK, Concepts of Modern Physics, 4th, A. Beiser, McGraw-Hill (International), 1987, 978-0-07-100144-1,
- BOOK, Physics with Modern Applications, L.H. Greenberg, Holt-Saunders International W.B. Saunders and Co, 1978, 978-0-7216-4247-5, registration,weblink
- BOOK, 12â13, R.G. Lerner, Rita G. Lerner, G.L. Trigg, Encyclopaedia of Physics, VHC Publishers, Hans Warlimont, Springer, 2nd, 2005, 978-0-07-025734-4,
- BOOK, Principles of Physics, J.B. Marion, W.F. Hornyak, Holt-Saunders International Saunders College, 1984, 978-4-8337-0195-2,
- BOOK, The Physics of Vibrations and Waves, 3rd, H.J. Pain, John Wiley & Sons, 1983, 978-0-471-90182-2,
- BOOK, C.B. Parker, McGraw Hill Encyclopaedia of Physics, McGraw Hill, 2nd, 1994, 978-0-07-051400-3,weblink
- BOOK, R. Penrose, The Road to Reality, Vintage books, 2007, 978-0-679-77631-4, The Road to Reality,
- BOOK, P.A. Tipler, G. Mosca, Physics for Scientists and Engineers: With Modern Physics, W.H. Freeman and Co, 6th, 2008, 978-1-4292-0265-7,
- BOOK, P.M. Whelan, M.J. Hodgeson, Essential Principles of Physics, John Murray, 2nd, 1978, 978-0-7195-3382-2,
External links
- Magnetic Field Strength Converter
- Electromagnetic Force â from Eric Weisstein's World of Physics
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