FACTOID # 30: If Alaska were its own country, it would be the 26th largest in total area, slightly larger than Iran.
 
 Home   Encyclopedia   Statistics   States A-Z   Flags   Maps   FAQ   About 
   
 
WHAT'S NEW
RELATED ARTICLES
People who viewed "Magnetism" also viewed:
 

SEARCH ALL

FACTS & STATISTICS    Advanced view

Search encyclopedia, statistics and forums:

 

 

(* = Graphable)

 

 


Encyclopedia > Magnetism
Electromagnetism
Electricity · Magnetism
Electrostatics
Electric charge
Coulomb's law
Electric field
Gauss's law
Electric potential
Electric dipole moment
Magnetostatics
Ampère's circuital law
Magnetic field
Magnetic flux
Biot-Savart law
Magnetic dipole moment
Electrodynamics
Electrical current
Lorentz force law
Electromotive force
(EM) Electromagnetic induction
Faraday-Lenz law
Displacement current
Maxwell's equations
(EMF) Electromagnetic field
(EM) Electromagnetic radiation
Electrical Network
Electrical conduction
Electrical resistance
Capacitance
Inductance
Impedance
Resonant cavities
Waveguides
Tensors in Relativity
Electromagnetic tensor
Electromagnetic stress-energy tensor
This box: view  talk  edit

In physics, magnetism is one of the phenomena by which materials exert attractive or repulsive forces on other materials. Some well known materials that exhibit easily detectable magnetic properties (called magnets) are nickel, iron and their alloys; however, all materials are influenced to greater or lesser degree by the presence of a magnetic field. Magnetism may refer to: In physics, magnetism is one of the phenomena by which materials exert an attractive or repulsive force on other materials. ... Image File history File links Solenoid. ... Electromagnetism is the physics of the electromagnetic field: a field which exerts a force on particles that possess the property of electric charge, and is in turn affected by the presence and motion of those particles. ... Electricity (from New Latin ēlectricus, amberlike) is a general term for a variety of phenomena resulting from the presence and flow of electric charge. ... Electrostatics (also known as static electricity) is the branch of physics that deals with the phenomena arising from what seem to be stationary electric charges. ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ... Coulombs torsion balance In physics, Coulombs law is an inverse-square law indicating the magnitude and direction of electrostatic force that one stationary, electrically charged object of small dimensions (ideally, a point source) exerts on another. ... In physics, the space surrounding an electric charge or in the presence of a time-varying magnetic field has a property called an electric field. ... In physics and mathematical analysis, Gausss law is the electrostatic application of the generalized Gausss theorem giving the equivalence relation between any flux, e. ... This article does not cite any references or sources. ... In physics, the electric dipole moment is a measure of the polarity of a system of electric charges. ... Magnetostatics is the study of static magnetic fields. ... In physics, Ampères Circuital law, discovered by André-Marie Ampère, relates the circulating magnetic field in a closed loop to the electric current passing through the loop. ... Magnetic field lines shown by iron filings In physics, the space surrounding moving electric charges, changing electric fields and magnetic dipoles contains a magnetic field. ... Magnetic flux, represented by the Greek letter Φ (phi), is a measure of quantity of magnetism, taking account of the strength and the extent of a magnetic field. ... The Biot-Savart law is a physical law with applications in both electromagnetics and fluid dynamics. ... A bar magnet. ... Classical electrodynamics (or classical electromagnetism) is a theory of electromagnetism that was developed over the course of the 19th century, most prominently by James Clerk Maxwell. ... In electricity, current is the rate of flow of charges, usually through a metal wire or some other electrical conductor. ... Lorentz force. ... Electromotive force (emf) is the amount of energy gained per unit charge that passes through a device in the opposite direction to the electric field existing across that device. ... For magnetic induction, see Magnetic field. ... Faradays law of induction (more generally, the law of electromagnetic induction) states that the induced emf (electromotive force) in a closed loop equals the negative of the time rate of change of magnetic flux through the loop. ... Displacement current is a quantity related to changing electric field. ... For thermodynamic relations, see Maxwell relations. ... The electromagnetic field is a physical field that is produced by electrically charged objects and which affects the behaviour of charged objects in the vicinity of the field. ... Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... This article does not cite any references or sources. ... Conduction is the movement of electrically charged particles through a transmission medium (electrical conductor). ... Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... Capacitance is a measure of the amount of electric charge stored (or separated) for a given electric potential. ... An electric current i flowing around a circuit produces a magnetic field and hence a magnetic flux Φ through the circuit. ... Electrical impedance, or simply impedance, is a measure of opposition to a sinusoidal alternating electric current. ... A resonator is a device or part that vibrates (or oscillates) with waves. ... It has been suggested that this article or section be merged with Waveguide (optics). ... Two-dimensional analogy of space-time curvature described in General Relativity. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... In physics, the electromagnetic stress-energy tensor is the portion of the stress-energy tensor due to the electromagnetic field. ... A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ... A phenomenon (plural: phenomena) is an observable event, especially something special (literally something that can be seen from the Greek word phainomenon = observable). ... material is the substance or matter from which something is or can be made, or also items needed for doing or creating something. ... For other uses, see Force (disambiguation). ... For other uses, see Magnet (disambiguation). ... For other uses, see Nickel (disambiguation). ... For other uses, see Iron (disambiguation). ... An alloy is a homogeneous hybrid of two or more elements, at least one of which is a metal, and where the resulting material has metallic properties. ... Magnetic field lines shown by iron filings In physics, the space surrounding moving electric charges, changing electric fields and magnetic dipoles contains a magnetic field. ...


Magnetism also has other manifestations in physics, particularly as one of the two components of electromagnetic waves such as light. Electromagnetic radiation is a propagating wave in space with electric and magnetic components. ... This article does not cite any references or sources. ...

Contents

Brief and qualitative explanation of magnetism

Every electron is, by its nature, a small magnet (see Electron magnetic dipole moment). Ordinarily, the countless electrons in a material are randomly oriented in different directions, leaving no effect on average, but in a magnet the electrons tend to face the same way, so they all pull together, thus creating a strong total magnetic force. In atomic physics, the magnetic dipole moment of an electron is involved in a variety of important atomic processes and effects. ...


History

Aristotle attributes the first of what might be called a scientific discussion on magnetism to Thales, who lived from about 625 BC to about 545 BC. [1] In China, the earliest literary reference to magnetism lies in a 4th century BC book called Book of the Devil Valley Master (鬼谷子): "The lodestone makes iron come or it attracts it."[1] The earliest mention of the attraction of a needle appears in a work composed between 20 and 100 AD (Louen-heng): "A lodestone attracts a needle."[2] The ancient Chinese scientist Shen Kuo (1031-1095) was the first person to write of the magnetic needle compass and improved the accuracy of navigation by employing the astronomical concept of true north (Dream Pool Essays, 1088 AD), and by the 12th century the Chinese were known to use the lodestone compass for navigation. Alexander Neckham, by 1187, was the first in Europe to describe the compass and its use for navigation. In 1269 Peter Peregrinus wrote the Epistola de Magnete, the first extant treatise describing the properties of magnets. This article is about the philosopher. ... For the Defense and Security Company, see Thales Group. ... The 4th century BC started the first day of 400 BC and ended the last day of 301 BC. It is considered part of the Classical era, epoch, or historical period. ... For other uses, see Iron (disambiguation). ... This is a Chinese name; the family name is Shen Shen Kuo or Shen Kua (Chinese: ; pinyin: ) (1031–1095) was a polymathic Chinese scientist and statesman of the Song Dynasty (960–1279). ... Events Collapse of the Moorish Caliphate of Córdoba. ... Events The country of Portugal is established for the second time. ... Astronomy, which etymologically means law of the stars, (from Greek: αστρονομία = άστρον + νόμος) is a science involving the observation and explanation of events occurring outside Earth and its atmosphere. ... True Pizza is a navigational term referring to the direction of the North Pole relative to the navigators position. ... Shen Kuo (沈括) (1031-1095 AD) The Dream Pool Essays (Pinyin: Meng Xi Bi Tan; Wade-Giles: Meng Chi Pi Tan Chinese: 梦溪笔谈) was an extensive book written by the polymath Chinese scientist and statesman Shen Kuo (1031-1095) by 1088 AD, during the Song Dynasty (960-1279) of China. ... This article is about the navigational instrument. ... Alexander Neckam (September 8, 1157 _ 1217), was an English scientist and teacher. ... For other uses, see Europe (disambiguation). ... Pivoting compass needle in a 14th century handcopy of Peters Epistola de magnete (1269) Peter of Maricourt (Peter Peregrinus of Maricourt;[1] French Pierre Pèlerin de Maricourt; Latin Petrus Peregrinus de Maharncuria) (fl. ...


An understanding of the relationship between electricity and magnetism began in 1819 with work by Hans Christian Oersted, a professor at the University of Copenhagen discovered more or less by accident that an electric current could influence a compass needle. This landmark experiment is known as Oersted's Experiment. Several other experiments followed, with André-Marie Ampère, Carl Friedrich Gauss, Michael Faraday, and others finding further links between magnetism and electricity. James Clerk Maxwell synthesized and expanded these insights into Maxwell's equations, unifying electricity, magnetism, and optics into the field of electromagnetism. In 1905, Einstein used these laws in motivating his theory of special relativity[3], in the process showing that electricity and magnetism are fundamentally interlinked and inseparable. Electricity (from New Latin Ä“lectricus, amberlike) is a general term for a variety of phenomena resulting from the presence and flow of electric charge. ... “Ørsted” redirects here. ... André-Marie Ampère (January 20, 1775 – June 10, 1836), was a French physicist who is generally credited as one of the main discoverers of electromagnetism. ... Johann Carl Friedrich Gauss or Gauß ( ; Latin: ) (30 April 1777 – 23 February 1855) was a German mathematician and scientist of profound genius who contributed significantly to many fields, including number theory, analysis, differential geometry, geodesy, electrostatics, astronomy, and optics. ... Michael Faraday, FRS (September 22, 1791 – August 25, 1867) was an English chemist and physicist (or natural philosopher, in the terminology of that time) who contributed to the fields of electromagnetism and electrochemistry. ... James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish mathematician and theoretical physicist from Edinburgh, Scotland, UK. His most significant achievement was aggregating a set of equations in electricity, magnetism and inductance — eponymously named Maxwells equations — including an important modification (extension) of the Ampères... For thermodynamic relations, see Maxwell relations. ... For the book by Sir Isaac Newton, see Opticks. ... Electromagnetism is the physics of the electromagnetic field: a field which exerts a force on particles that possess the property of electric charge, and is in turn affected by the presence and motion of those particles. ... For a less technical and generally accessible introduction to the topic, see Introduction to special relativity. ...


Electromagnetism has continued to develop into the twentieth century, being incorporated into the more fundamental theories of gauge theory, quantum electrodynamics, electroweak theory, and finally the standard model. In physics, gauge theories are a class of physical theories based on the idea that symmetry transformations can be performed locally as well as globally. ... Quantum electrodynamics (QED) is a relativistic quantum field theory of electrodynamics. ... In physics, the electroweak theory presents a unified description of two of the four fundamental forces of nature: electromagnetism and the weak nuclear force. ... The Standard Model of Fundamental Particles and Interactions For the Standard Model in Cryptography, see Standard Model (cryptography). ...


Physics of magnetism

Magnetism, electricity, and special relativity

Main article: Electromagnetism

As a consequence of Einstein's theory of special relativity, electricity and magnetism are understood to be fundamentally interlinked. Both magnetism without electricity, and electricity without magnetism, are inconsistent with special relativity, due to such effects as length contraction, time dilation, and the fact that the magnetic force is velocity-dependent. However, when both electricity and magnetism are taken into account, the resulting theory (electromagnetism) is fully consistent with special relativity[4][5]. In particular, a phenomenon that appears purely electric to one observer may be purely magnetic to another, or more generally the relative contributions of electricity and magnetism are dependent on the frame of reference. Thus, special relativity "mixes" electricity and magnetism into a single, inseparable phenomenon called electromagnetism (analogously to how special relativity "mixes" space and time into spacetime). Electromagnetism is the physics of the electromagnetic field: a field which exerts a force on particles that possess the property of electric charge, and is in turn affected by the presence and motion of those particles. ... For a less technical and generally accessible introduction to the topic, see Introduction to special relativity. ... Length contraction, according to Albert Einsteins special theory of relativity, is the decrease in length experienced by people or objects traveling at a substantial fraction of the speed of light. ... Time dilation is the phenomenon whereby an observer finds that anothers clock which is physically identical to their own is ticking at a slower rate as measured by their own clock. ... In physics, magnetism is a phenomenon by which materials exert an attractive or repulsive force on other materials. ... Electromagnetism is the physics of the electromagnetic field: a field which exerts a force on particles that possess the property of electric charge, and is in turn affected by the presence and motion of those particles. ... For other uses of this term, see Spacetime (disambiguation). ...


Magnetic fields and forces

Magnetic lines of force of a bar magnet shown by iron filings on paper
Magnetic lines of force of a bar magnet shown by iron filings on paper
Main article: magnetic field

The phenomenon of magnetism is "mediated" by the magnetic field -- i.e., an electric current or magnetic dipole creates a magnetic field, and that field, in turn, imparts magnetic forces on other particles that are in the fields. Image File history File links Magnet0873. ... Image File history File links Magnet0873. ... Magnetic field lines shown by iron filings In physics, the space surrounding moving electric charges, changing electric fields and magnetic dipoles contains a magnetic field. ... Magnetic field lines shown by iron filings In physics, the space surrounding moving electric charges, changing electric fields and magnetic dipoles contains a magnetic field. ...


To an excellent approximation (but ignoring some quantum effects---see quantum electrodynamics), Maxwell's equations (which simplify to the Biot-Savart law in the case of steady currents) describe the origin and behavior of the fields that govern these forces. Therefore magnetism is seen whenever electrically charged particles are in motion---for example, from movement of electrons in an electric current, or in certain cases from the orbital motion of electrons around an atom's nucleus. They also arise from "intrinsic" magnetic dipoles arising from quantum effects, i.e. from quantum-mechanical spin. Quantum electrodynamics (QED) is a relativistic quantum field theory of electrodynamics. ... For thermodynamic relations, see Maxwell relations. ... The Biot-Savart law is a physical law with applications in both electromagnetics and fluid dynamics. ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ... This article or section is in need of attention from an expert on the subject. ... For other uses, see Electron (disambiguation). ... Electric current is the flow (movement) of electric charge. ... In the article on Magnetism, it states that the physical cause of an atomic magnetic dipole (or moment) is two kinds of movement of electrons. ... This article is about the electromagnetic phenomenon. ... In physics, spin refers to the angular momentum intrinsic to a body, as opposed to orbital angular momentum, which is the motion of its center of mass about an external point. ...


The same situations which create magnetic fields (charge moving in a current or in an atom, and intrinsic magnetic dipoles) are also the situations in which a magnetic field has an effect, creating a force. Following is the formula for moving charge; for the forces on an intrinsic dipole, see magnetic dipole. For other uses, see Force (disambiguation). ... This article is about the electromagnetic phenomenon. ...


When a charged particle moves through a magnetic field B, it feels a force F given by the cross product: Magnetic field lines shown by iron filings In physics, the space surrounding moving electric charges, changing electric fields and magnetic dipoles contains a magnetic field. ... For other uses, see Force (disambiguation). ... For the cross product in algebraic topology, see Künneth theorem. ...

vec{F} = q vec{v} times vec{B}

where q, is the electric charge of the particle, vec{v} , is the velocity vector of the particle, and vec{B} , is the magnetic field. Because this is a cross product, the force is perpendicular to both the motion of the particle and the magnetic field. It follows that the magnetic force does no work on the particle; it may change the direction of the particle's movement, but it cannot cause it to speed up or slow down. The magnitude of the force is Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ... This article is about velocity in physics. ... A vector going from A to B. In physics and in vector calculus, a spatial vector, or simply vector, is a concept characterized by a magnitude and a direction. ... Magnetic field lines shown by iron filings In physics, the space surrounding moving electric charges, changing electric fields and magnetic dipoles contains a magnetic field. ... Fig. ... In physics, mechanical work is the amount of energy transferred by a force. ...

F = q v B sintheta,

where theta , is the angle between the vec{v} , and vec{B} , vectors.


One tool for determining the direction of the velocity vector of a moving charge, the magnetic field, and the force exerted is labeling the index finger "V", the middle finger "B", and the thumb "F" with your right hand. When making a gun-like configuration (with the middle finger crossing under the index finger), the fingers represent the velocity vector, magnetic field vector, and force vector, respectively. See also right hand rule. This article is about velocity in physics. ... The Index finger The index finger, pointer finger or forefinger is the second digit of a human hand, located between the thumb and the middle finger. ... This article is about the vulgar gesture. ... For other uses, see Thumb (disambiguation). ... The right hand rule is also an algorithm used to solve Mazes In mathematics and physics, the right-hand rule is a convention for determining relative directions of certain vectors. ...


Lenz's law gives the direction of the induced electromotive force (emf) and current resulting from electromagnetic induction. German physicist Heinrich Lenz formulated it in 1834. Lenzs law (pronounced (IPA) ) gives the direction of the induced electromotive force (emf) and current resulting from electromagnetic induction. ...


Magnetic dipoles

Main article: magnetic dipole

A very common source of magnetic field seen in nature is a dipoles, having a "South pole" and a "North pole"; terms dating back to the use of magnets as compasses, interacting with the Earth's magnetic field to indicate North and South on the globe. Since opposite ends of magnets are attracted, the 'north' magnetic pole of the earth must be magnetically 'south'. This article is about the electromagnetic phenomenon. ... Magnetic field lines shown by iron filings In physics, the space surrounding moving electric charges, changing electric fields and magnetic dipoles contains a magnetic field. ... The Earths magnetic field, which is approximately a dipole. ... For other uses, see South Pole (disambiguation). ... For other uses, see North Pole (disambiguation). ... This article is about the navigational instrument. ... The magnetosphere shields the surface of the Earth from the charged particles of the solar wind. ... World globe A Baroque era celestial globe A globe is a three-dimensional scale model of a spheroid celestial body such as a planet, star or moon, in particular Earth, or, alternatively, a spherical representation of the sky with the stars (but without the Sun, Moon, or planets, because their...


A magnetic field contains energy, and physical systems stabilize into the configuration with the lowest energy. Therefore, when placed in a magnetic field, a magnetic dipole tends to align itself in opposed polarity to that field, thereby canceling the net field strength as much as possible and lowering the energy stored in that field to a minimum. For instance, two identical bar magnets placed side-to-side normally line up North to South, resulting in a much smaller net magnetic field, and resist any attempts to reorient them to point in the same direction. The energy required to reorient them in that configuration is then stored in the resulting magnetic field, which is double the strength of the field of each individual magnet. (This is, of course, why a magnet used as a compass interacts with the Earth's magnetic field to indicate North and South).


An alternative, equivalent formulation, which is often easier to apply but perhaps offers less insight, is that a magnetic dipole in a magnetic field experiences a torque and a force which can be expressed in terms of the field and the strength of the dipole (i.e., its magnetic dipole moment). For these equations, see magnetic dipole. Torque applied via an adjustable end wrench Relationship between force, torque, and momentum vectors in a rotating system In physics, torque (or often called a moment) can informally be thought of as rotational force or angular force which causes a change in rotational motion. ... For other uses, see Force (disambiguation). ... In physics, the magnetic moment of an object is a vector relating the aligning torque in a magnetic field experienced by the object to the field vector itself. ... This article is about the electromagnetic phenomenon. ...


Atomic magnetic dipoles

The physical cause of the magnetism of objects, as distinct from electrical currents, is the atomic magnetic dipole. Magnetic dipoles, or magnetic moments, result on the atomic scale from the two kinds of movement of electrons. The first is the orbital motion of the electron around the nucleus; this motion can be considered as a current loop, resulting in an orbital dipole magnetic moment. The second, much stronger, source of electronic magnetic moment is due to a quantum mechanical property called the spin dipole magnetic moment (although current quantum mechanical theory states that electrons neither physically spin, nor orbit the nucleus). In electricity, current is the rate of flow of charges, usually through a metal wire or some other electrical conductor. ... The Earths magnetic field, which is approximately a dipole. ... The nucleus of an atom is the very small dense region, of positive charge, in its centre consisting of nucleons (protons and neutrons). ... For a less technical and generally accessible introduction to the topic, see Introduction to quantum mechanics. ... In physics, spin refers to the angular momentum intrinsic to a body, as opposed to orbital angular momentum, which is the motion of its center of mass about an external point. ...

Dipole moment of a bar magnet.

The overall magnetic moment of the atom is the net sum of all of the magnetic moments of the individual electrons. Because of the tendency of magnetic dipoles to oppose each other to reduce the net energy, in an atom the opposing magnetic moments of some pairs of electrons cancel each other, both in orbital motion and in spin magnetic moments. Thus, in the case of an atom with a completely filled electron shell or subshell, the magnetic moments normally completely cancel each other out and only atoms with partially-filled electron shells have a magnetic moment, whose strength depends on the number of unpaired electrons. Image File history File links Magnetic_dipole_moment. ... Image File history File links Magnetic_dipole_moment. ... Example of a sodium electron shell model An electron shell, also known as a main energy level, is a group of atomic orbitals with the same value of the principal quantum number n. ...


The differences in configuration of the electrons in various elements thus determine the nature and magnitude of the atomic magnetic moments, which in turn determine the differing magnetic properties of various materials. Several forms of magnetic behavior have been observed in different materials, including:

Levitating pyrolytic carbon Diamagnetism is a form of magnetism that is only exhibited by a substance in the presence of an externally applied magnetic field. ... Simple Illustration of a paramagnetic probe made up from miniature magnets. ... Molecular magnets are systems where a permanent magnetization and magnetic hysteresis can be achieved (although usually at extremely low temperatures) not through a three-dimensional magnetic ordering, but as a purely one-molecule phenomenon. ... Ferromagnetism is the phenomenon by which materials, such as iron, in an external magnetic field become magnetized and remain magnetized for a period after the material is no longer in the field. ... In materials that exhibit antiferromagnetism, the spins of electrons align in a regular pattern with neighboring spins pointing in opposite directions. ... In physics, a ferrimagnetic material is one in which the magnetic moment of the atoms on different sublattices oppose as in antiferromagnetism but the opposing moments are unequal and a spontaneous magnetization remains. ... Metamagnetism is a physical state of matter characterized by a superlinear increase of magnetization over a narrow range of applied magnetic field. ... A spin glass is a disordered material exhibiting high magnetic frustration. ... Superparamagnetism refers to materials which become magnetic in the presence of an external magnet, but revert to a non magnetic state when the external magnet is removed. ...

Magnetic monopoles

Main article: Magnetic monopole

Since a bar magnet gets its ferromagnetism from microscopic electrons distributed evenly throughout the bar, when a bar magnet is cut in half, each of the resulting pieces is a smaller bar magnet. Even though a magnet is said to have a north pole and a south pole, these two poles cannot be separated from each other. A monopole — if such a thing exists — would be a new and fundamentally different kind of magnetic object. It would act as an isolated north pole, not attached to a south pole, or vice versa. Monopoles would carry "magnetic charge" analogous to electric charge. Despite systematic searches since 1931, as of 2006, they have never been observed, and could very well not exist.[6] In physics, a magnetic monopole is a hypothetical particle that may be loosely described as a magnet with only one pole (see electromagnetic theory for more on magnetic poles). ... 2006 is a common year starting on Sunday of the Gregorian calendar. ...


Nevertheless, some theoretical physics models predict the existence of these magnetic monopoles. Paul Dirac observed in 1931 that, because electricity and magnetism show a certain symmetry, just as quantum theory predicts that individual positive or negative electric charges can be observed without the opposing charge, isolated South or North magnetic poles should be observable. Using quantum theory Dirac showed that if magnetic monopoles exist, then one could explain the quantization of electric charge---that is, why the observed elementary particles carry charges that are multiples of the charge of the electron. Theoretical physics employs mathematical models and abstractions of physics, as opposed to experimental processes, in an attempt to understand nature. ... In physics, magnetic monopole is a term describing a hypothetical particle that could be quickly clarified to a person familiar with magnets but not electromagnetic theory as a magnet with only one pole. In more accurate terms, it would have net magnetic charge. Interest in the concept stems from particle... Paul Adrien Maurice Dirac, OM, FRS (IPA: [dɪræk]) (August 8, 1902 – October 20, 1984) was a British theoretical physicist and a founder of the field of quantum physics. ... Electricity (from New Latin ēlectricus, amberlike) is a general term for a variety of phenomena resulting from the presence and flow of electric charge. ... Sphere symmetry group o. ... Quantum electrodynamics (QED) is a relativistic quantum field theory of electrodynamics. ... A negative number is a number that is less than zero, such as −3. ... In particle physics, an elementary particle is a particle of which other, larger particles are composed. ...


Certain grand unified theories predict the existence of monopoles which, unlike elementary particles, are solitons (localized energy packets). Using these models to estimate the number of monopoles created in the big bang, the initial results that contradicted cosmological observations---the monopoles would have been so plentiful and massive that they would have long since halted the expansion of the universe. However, the idea of inflation (for which this problem served as a partial motivation) was successful in solving this problem, creating models in which monopoles existed but were rare enough to be consistent with current observations.[7] Grand unification, grand unified theory, or GUT is a theory in physics that unifies the strong interaction and electroweak interaction. ... A soliton is a self-reinforcing solitary wave caused by nonlinear effects in the medium. ... For other uses, see Big Bang (disambiguation). ...


Types of magnets

Electromagnets

Main article: Electromagnet

An electromagnet is a magnet made from electrical wire wound around a magnetic material, such as iron. This form of magnet is useful in cases where a magnet must be switched on or off; for instance, large cranes to lift junked automobiles. An electromagnet is a type of magnet in which the magnetic field is produced by a flow of electric current. ... A modern crawler type derrick crane with outriggers. ...


For the case of electric current moving through a wire, the resulting field is directed according to the "right hand rule." If the right hand is used as a model, and the thumb of the right hand points along the wire from positive towards the negative side ("conventional current", the reverse of the direction of actual movement of electrons), then the magnetic field will wrap around the wire in the direction indicated by the fingers of the right hand. As can be seen geometrically, if a loop or helix of wire is formed such that the current is traveling in a circle, then all of the field lines in the center of the loop are directed in the same direction, resulting in a magnetic dipole whose strength depends on the current around the loop, or the current in the helix multiplied by the number of turns of wire. In the case of such a loop, if the fingers of the right hand are directed in the direction of conventional current flow (i.e., positive to negative, the opposite direction to the actual flow of electrons), the thumb will point in the direction corresponding to the North pole of the dipole. Electric current is the flow (movement) of electric charge. ... A helix (pl: helices), from the Greek word έλικας/έλιξ, is a twisted shape like a spring, screw or a spiral (correctly termed helical) staircase. ... Circle illustration This article is about the shape and mathematical concept of circle. ... The Earths magnetic field, which is approximately a dipole. ...


Permanent and temporary magnets

Main article: Magnet

A permanent magnet retains its magnetism without an external magnetic field whereas a temporary magnet is only magnetic while within another magnetic field. Inducing magnetism in steel results in a permanent magnet but iron loses its magnetism when the inducing field is withdrawn. A temporary magnet such as iron is thus a good material for electromagnets. Magnets are made by stroking with another magnet, tapping while fixed in a magnetic field or placing inside a solenoid coil supplied with a direct current. A permanent magnet may be de-magnetised by subjecting it to heating or sharp blows or placing it inside a solenoid supplied with a reducing alternating current. For other uses, see Magnet (disambiguation). ... Magnetic field lines shown by iron filings In physics, the space surrounding moving electric charges, changing electric fields and magnetic dipoles contains a magnetic field. ... For other uses, see Solenoid (disambiguation). ...


Units of electromagnetism

SI units related to magnetism

SI electromagnetism units
Symbol [citation needed] Name of Quantity Derived Units Unit Base Units
I Magnitude of current ampere (SI base unit) A A = W/V = C/s
q Electric charge, Quantity of electricity coulomb C A·s
V Potential difference or Electromotive force volt V J/C = kg·m2·s−3·A−1
R, Z, X Resistance, Impedance, Reactance ohm Ω V/A = kg·m2·s−3·A−2
ρ Resistivity ohm metre Ω·m kg·m3·s−3·A−2
P Power, Electrical watt W V·A = kg·m2·s−3
C Capacitance farad F C/V = kg−1·m−2·A2·s4
Elastance reciprocal farad F−1 V/C = kg·m2·A−2·s−4
ε Permittivity farad per metre F/m kg−1·m−3·A2·s4
χe Electric susceptibility (dimensionless) - -
G, Y, B Conductance, Admittance, Susceptance siemens S Ω−1 = kg−1·m−2·s3·A2
σ Conductivity siemens per metre S/m kg−1·m−3·s3·A2
B Magnetic flux density, Magnetic induction tesla T Wb/m2 = kg·s−2·A−1 = N·A−1·m−1
Φm Magnetic flux weber Wb V·s = kg·m2·s−2·A−1
H Magnetic field strength,Magnetic field intensity ampere per metre A/m A·m−1
Reluctance ampere-turn per weber A/Wb kg−1·m−2·s2·A2
L Inductance henry H Wb/A = V·s/A = kg·m2·s−2·A−2
μ Permeability henry per metre H/m kg·m·s−2·A−2
χm Magnetic susceptibility (dimensionless)
Π and Π * Electric and Magnetic hertzian vector potentials n/a n/a

Look up si, Si, SI in Wiktionary, the free dictionary. ... Electromagnetism is the physics of the electromagnetic field: a field which exerts a force on particles that possess the property of electric charge, and is in turn affected by the presence and motion of those particles. ... In electricity, current refers to electric current, which is the flow of electric charge. ... For other uses, see Ampere (disambiguation). ... Look up si, Si, SI in Wiktionary, the free dictionary. ... Electric charge is a fundamental conserved property of some subatomic particles, which determines their electromagnetic interaction. ... In physics the term quantity of electricity refers to the quantity of electric charge. ... The coulomb (symbol: C) is the SI unit of electric charge. ... Potential difference is a quantity in physics related to the amount of energy that would be required to move an object from one place to another against various types of force. ... Electromotive force (emf) is the amount of energy gained per unit charge that passes through a device in the opposite direction to the electric field existing across that device. ... Josephson junction array chip developed by NIST as a standard volt. ... Electrical resistance is a measure of the degree to which an electrical component opposes the passage of current. ... Electrical impedance, or simply impedance, is a measure of opposition to a sinusoidal alternating electric current. ... It has been suggested that Electric reactance be merged into this article or section. ... The ohm (symbol: Ω) is the SI unit of electric resistance. ... // Headline text POOP!! Danny Hornsby (also known as Gnome) is a measure indicating how strongly a Gnome can opposes the flow of electric current. ... The ohm (symbol: Ω) is the SI unit of electric resistance. ... This article is about the unit of length. ... Transmission lines in Lund, Sweden Electric power, often known as power or electricity, involves the production and delivery of electrical energy in sufficient quantities to operate domestic appliances, office equipment, industrial machinery and provide sufficient energy for both domestic and commercial lighting, heating, cooking and industrial processes. ... For other uses, see Watt (disambiguation). ... Capacitance is a measure of the amount of electric charge stored (or separated) for a given electric potential. ... Examples of various types of capacitors. ... Electrical elastance is the inverse of capacitance. ... Examples of various types of capacitors. ... Permittivity is a physical quantity that describes how an electric field affects and is affected by a dielectric medium and is determined by the ability of a material to polarize in response to an applied electric field, and thereby to cancel, partially, the field inside the material. ... Examples of various types of capacitors. ... This article is about the unit of length. ... The electric susceptibility χe of a dielectric material is a measure of how easily it polarizes in response to an electric field. ... Electrical conductance is the reciprocal of electrical resistance. ... In electrical engineering, the admittance (Y) is the inverse of the impedance (Z). ... In electrical engineering, the susceptance (B) is the imaginary part of the admittance. ... The siemens (symbol: S) is the SI derived unit of electric conductance. ... Electrical conductivity or specific conductivity is a measure of a materials ability to conduct an electric current. ... The siemens (symbol: S) is the SI derived unit of electric conductance. ... This article is about the unit of length. ... Magnetic field lines shown by iron filings In physics, the space surrounding moving electric charges, changing electric fields and magnetic dipoles contains a magnetic field. ... SI unit. ... Magnetic flux, represented by the Greek letter Φ (phi), is a measure of quantity of magnetism, taking account of the strength and the extent of a magnetic field. ... In physics, the weber (symbol: Wb) is the SI unit of magnetic flux. ... Magnetic field lines shown by iron filings In physics, the space surrounding moving electric charges, changing electric fields and magnetic dipoles contains a magnetic field. ... For other uses, see Ampere (disambiguation). ... This article is about the unit of length. ... Magnetic reluctance is the resistance of a material to a magnetic field. ... The ampere-turn (AT) is a unit of magnetomotive force or magnetic potential, represented by a direct current of one ampere flowing in a single-turn loop in a vacuum. ... In physics, the weber (symbol: Wb) is the SI unit of magnetic flux. ... An electric current i flowing around a circuit produces a magnetic field and hence a magnetic flux Φ through the circuit. ... An inductor. ... In electromagnetism, permeability is the degree of magnetization of a material that responds linearly to an applied magnetic field. ... An inductor. ... This article is about the unit of length. ... In physics and electrical engineering, the magnetic susceptibility is the degree of magnetization of a material in response to an applied magnetic field. ... This article does not cite any references or sources. ...

Other units

The gauss, abbreviated as G, is the cgs unit of magnetic flux density (B), named after the German mathematician and physicist Carl Friedrich Gauss. ... This article or section is in need of attention from an expert on the subject. ... The former Weights and Measures office in Middlesex, England. ... Current flowing through a wire produces a magnetic field (B, labeled M here) around the wire. ... Electromagnetic induction is the production of an electrical potential difference (or voltage) across a conductor situated in a changing magnetic field. ... The oersted is old CGS unit of magnetic field strength (or magnetic induction). ... This article or section is in need of attention from an expert on the subject. ... The former Weights and Measures office in Middlesex, England. ... In physics, a magnetic field is an entity produced by moving electric charges (electric currents) that exerts a force on other moving charges. ... The maxwell, abbreviated as Mx, is the compound derived CGS unit of magnetic flux. ... This article or section is in need of attention from an expert on the subject. ... Magnetic flux, represented by the Greek letter Φ (phi), is a measure of quantity of magnetism, taking account of the strength and the extent of a magnetic field. ... In electromagnetism, permeability is the degree of magnetization of a material that responds linearly to an applied magnetic field. ...

See also

Wikibooks
Wikibooks' [[wikibooks:|]] has more about this subject:
School science how-to

Image File history File links Wikibooks-logo-en. ... The magnetosphere shields the surface of the Earth from the charged particles of the solar wind. ... Electrostatics (also known as static electricity) is the branch of physics that deals with the phenomena arising from what seem to be stationary electric charges. ... Magnetostatics is the study of static magnetic fields. ... Electromagnetism is the physics of the electromagnetic field: a field which exerts a force on particles that possess the property of electric charge, and is in turn affected by the presence and motion of those particles. ... Lenzs law (pronounced (IPA) ) gives the direction of the induced electromotive force (emf) and current resulting from electromagnetic induction. ... A plastic magnet is a non-metallic magnet. ... For other uses, see Magnet (disambiguation). ... Artists conception of a magnetar, with magnetic field lines A magnetar is a neutron star with an extremely powerful magnetic field, the decay of which powers the emission of copious amounts of high-energy electromagnetic radiation, particularly X-rays and gamma-rays. ... Magnetic field lines shown by iron filings In physics, the space surrounding moving electric charges, changing electric fields and magnetic dipoles contains a magnetic field. ... A magnetic bearing is a bearing which supports a load using magnetic levitation. ... Magnetic refrigeration is a cooling technology based on the magnetocaloric effect. ... Magnet therapy, or magnetic therapy, or magnotherapy is a form of alternative medicine involving magnetic fields. ... A magnetic circuit is a closed path containing a magnetic flux. ... Magnetization is a property of some materials (e. ... Michael Faraday, FRS (September 22, 1791 – August 25, 1867) was an English chemist and physicist (or natural philosopher, in the terminology of that time) who contributed to the fields of electromagnetism and electrochemistry. ... General Micromagnetism deals with the interactions between magnetic moments on sub-micrometre length scales. ... James Clerk Maxwell (13 June 1831 – 5 November 1879) was a Scottish mathematician and theoretical physicist from Edinburgh, Scotland, UK. His most significant achievement was aggregating a set of equations in electricity, magnetism and inductance — eponymously named Maxwells equations — including an important modification (extension) of the Ampères... In material science, the Coercivity of a ferromagnetic material is the intensity of the magnetic field required to reduce the magnetization of that material to zero after the magnetization of the sample has reached saturation. ... An illustration of ferromagnetic magnon Spin waves are propagating disturbances in the ordering of magnetic materials. ... Spontaneous magnetization is the term used to describe the appearance of an ordered spin state at zero applied magnetic field in a ferromagnetic or ferrimagnetic material below a critical point called the Curie temperature or TC. At temperatures above TC, the material is paramagnetic and its magnetic behavior is dominated... Not to be confused with censure, censer, or censor. ... A magnetic stirrer is a type of laboratory equipment consisting of a rotating magnet or stationary electomagnets creating a rotating magnetic field. ... Levitating pyrolytic carbon Diamagnetism is a form of magnetism that is only exhibited by a substance in the presence of an externally applied magnetic field. ... Superdiamagnetism (or perfect diamagnetism) is a phenomenon occurring in certain materials at low temperatures, characterised by the complete absence of magnetic susceptibility and the exclusion of the interior magnetic field. ... Simple Illustration of a paramagnetic probe made up from miniature magnets. ... Superparamagnetism refers to materials which become magnetic in the presence of an external magnet, but revert to a non magnetic state when the external magnet is removed. ... Ferromagnetism is the phenomenon by which materials, such as iron, in an external magnetic field become magnetized and remain magnetized for a period after the material is no longer in the field. ... In materials that exhibit antiferromagnetism, the spins of electrons align in a regular pattern with neighboring spins pointing in opposite directions. ... In physics, a ferrimagnetic material is one in which the magnetic moment of the atoms on different sublattices oppose as in antiferromagnetism but the opposing moments are unequal and a spontaneous magnetization remains. ... Metamagnetism is a physical state of matter characterized by a superlinear increase of magnetization over a narrow range of applied magnetic field. ... A spin glass is a disordered material exhibiting high magnetic frustration. ...

References

  • Griffiths, David J. (1998). Introduction to Electrodynamics (3rd ed.). Prentice Hall. ISBN 0-13-805326-X. 
  • Tipler, Paul (2004). Physics for Scientists and Engineers: Electricity, Magnetism, Light, and Elementary Modern Physics (5th ed.). W. H. Freeman. ISBN 0-7167-0810-8. 
  • Furlani, Edward P. (2001). Permanent Magnet and Electromechanical Devices: Materials, Analysis and Applications. Academic Press. ISBN 0-12-269951-3. 
  1. ^ Li Shu-hua, “Origine de la Boussole 11. Aimant et Boussole,” Isis, Vol. 45, No. 2. (Jul., 1954), p.175
  2. ^ Li Shu-hua, “Origine de la Boussole 11. Aimant et Boussole,” Isis, Vol. 45, No. 2. (Jul., 1954), p.176
  3. ^ A. Einstein: "On the Electrodynamics of Moving Bodies", June 30, 1905. http://www.fourmilab.ch/etexts/einstein/specrel/www/.
  4. ^ A. Einstein: "On the Electrodynamics of Moving Bodies", June 30, 1905. http://www.fourmilab.ch/etexts/einstein/specrel/www/.
  5. ^ Griffiths, David J. (1998). Introduction to Electrodynamics, 3rd ed., Prentice Hall. ISBN 0-13-805326-X. , chapter 12
  6. ^ Milton mentions some inconclusive events (p.60) and still concludes that "no evidence at all of magnetic monopoles has survived" (p.3). Milton, Kimball A. (June 2006). "Theoretical and experimental status of magnetic monopoles". Reports on Progress in Physics 69 (6): 1637-1711. doi:10.1088/0034-4885/69/6/R02. .
  7. ^ Guth, Alan (1997). The Inflationary Universe: The Quest for a New Theory of Cosmic Origins. Perseus. ISBN 0-201-32840-2. .

David J. Griffiths is a U.S. physicist and educator. ... A digital object identifier (or DOI) is a standard for persistently identifying a piece of intellectual property on a digital network and associating it with related data, the metadata, in a structured extensible way. ... Alan Harvey Guth (born February 27, 1947) is a physicist and cosmologist. ...

External links

Look up Magnetism in
Wiktionary, the free dictionary.

  Results from FactBites:
 
magnet (0 words)
The crystals are used as magnetic "surveyor's spirit levels" that ensure that nests are aligned correctly and do not become lopsided, as it is believed that the crystals help the hornets to assess the symmetry and balance of the cells by comparing the magnetic field with the gravitational field.
Powerful magnetic fields in the vicinity of a television or monitor can distort the image and in some cases permanently magnetise the tube which leads to coloured patches on the screen and the tube must then be demagnetised or degaussed.
The magnetic history of the Earth as recorded in rocks in the various continents is the same but the the orientation of the magnetic information in the different continents is different thus indicating that the continents have moved over the Earth's surface.
magnetism — FactMonster.com (115 words)
electromagnet - electromagnet electromagnet, device in which magnetism is produced by an electric current.
pole, in electricity and magnetism - pole pole, in electricity and magnetism, point where electric or magnetic force appears to be...
magnetic flux - flux, magnetic flux, magnetic, in physics, term used to describe the total amount of magnetic field...
  More results at FactBites »

 
 

COMMENTARY     


Share your thoughts, questions and commentary here
Your name
Your comments

Want to know more?
Search encyclopedia, statistics and forums:

 


Press Releases |  Feeds | Contact
The Wikipedia article included on this page is licensed under the GFDL.
Images may be subject to relevant owners' copyright.
All other elements are (c) copyright NationMaster.com 2003-5. All Rights Reserved.
Usage implies agreement with terms, 1022, m