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## PowerPedia:Magnetism

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In Physics, magnetism is one of the There was an error working with the wiki: Code[38] by which There was an error working with the wiki: Code[39] exert an attractive or repulsive Force on other materials.

Some well known materials that exhibit easily detectable magnetic properties are There was an error working with the wiki: Code[40], some There was an error working with the wiki: Code[41]s, and the There was an error working with the wiki: Code[42] There was an error working with the wiki: Code[43] however, all materials are influenced to greater or lesser degree by the presence of a Magnetic field.

#### Physics of magnetism

" The Magnetism and magnetic field is a radiation of Waves magnetic force (magnetic force waves).

Magnetism is produced by Waves of magnetic force (magnetic force waves) .

The atoms in the magnet add their magnetic fields and thus enhance overall is causing an exponential growth that produces a chain reaction and this releases energy in waves of magnetic force thus creating the Magnetism and magnetic field .

Compression between Waves of magnetic force same polarity is magnetic repellency .

Connection and Annexation Waves of magnetic force different polarity is magnetic attraction .

(magnetic attraction is the unifying force of atomic magnetic fields ).quote by Author Juan Carlos Aviles Moran ".

Magnetic There was an error working with the wiki: Code[3] are fundamental forces that arise from the movement of electrical charge. There was an error working with the wiki: Code[4] are in There was an error working with the wiki: Code[5]. This can arise either from movement of There was an error working with the wiki: Code[6] and There was an error working with the wiki: Code[7] of electrons, resulting in what are known as "permanent magnets". Electron spin is the dominant effect within atoms. The so-called 'orbital motion' of electrons around the There was an error working with the wiki: Code[8] is a secondary effect that slightly modifies the magnetic field created by spin.

When given a treatment with There was an error working with the wiki: Code[44] in mind, depending on the frame of reference, electromagnetic forces acting on an object partition differently into magnetic and electric fields. In fact, for this reason, magnetism can be considered a direct consequence of relativity.

#### Charged particle in a magnetic field

When a charged particle moves through a Magnetic field B, it feels a Force F given by the There was an error working with the wiki: Code[45]:

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

where

q\, is the Electric charge of the particle

\vec{v} \, is the There was an error working with the wiki: Code[9] of the particle

\vec{B} \, is the Magnetic field.

Because this is a cross product, the force is There was an error working with the wiki: Code[10] on the particle it may change the direction of the particle's movement, but it cannot cause it to speed up or slow down.

This might give you pause: Simple bar magnets seem to be entirely able to pick up small metal objects, which certainly seems to require that they do work on those objects. As There was an error working with the wiki: Code[46] points out in his There was an error working with the wiki: Code[47] Introduction to Electrodynamics, this law is absolute - the magnetic field doesn't do any work. However, quite like the There was an error working with the wiki: Code[48] of an There was an error working with the wiki: Code[49], which also can't do work, the magnetic field can redirect the efforts of existing forces, and then those forces can indeed do work in the relevant direction.

One tool (often introduced in physics courses) for determining the direction of the Velocity vector of a moving charge, the magnetic field, and the force exerted is labeling the There was an error working with the wiki: Code[50] "V", the There was an error working with the wiki: Code[51] "B", and the There was an error working with the wiki: Code[52] "F". 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 There was an error working with the wiki: Code[53].

#### Magnetic dipoles

Normally, Magnetic fields are seen as There was an error working with the wiki: Code[54]s, having a "There was an error working with the wiki: Code[55]" and a "There was an error working with the wiki: Code[56]" terms dating back to the use of magnets as There was an error working with the wiki: Code[57]es, interacting with the There was an error working with the wiki: Code[58] to indicate North and South on the There was an error working with the wiki: Code[59].

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 normally line up North to South resulting in no 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).

#### Magnetic monopoles

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Contrary to normal experience, some There was an error working with the wiki: Code[11] or negative electric charges can be observed without the opposing charge, isolated South or North magnetic poles should be observable. In practice, however, although charged particles like protons and electrons can be easily isolated as individual electrical charges, magnetic south and north poles have not been found in isolation. Using quantum theory Dirac showed that if magnetic monopoles exist, then one could explain why the observed There was an error working with the wiki: Code[60] carry charges that are multiples of the charge of the electron.

In modern elementary particle theory, the quantization of charge is realized in a spontaneous breakdown of a non-There was an error working with the wiki: Code[12] gave rise to the currently-interesting idea of There was an error working with the wiki: Code[13].

#### Atomic magnetic dipoles

The physical cause of the magnetism of objects, as distinct from There was an error working with the wiki: Code[14] this motion can be considered as a current loop, resulting in an orbital dipole magnetic moment along the axis of the nucleus. The second, much stronger, source of electronic magnetic moment is due to a Quantum mechanics property called the There was an error working with the wiki: Code[15] dipole magnetic moment (although current quantum mechanical theory states that electrons neither physically spin, nor orbit the nucleus).

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 There was an error working with the wiki: Code[61] 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.

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:

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There was an error working with the wiki: Code[71]s, There was an error working with the wiki: Code[72]s with extremely powerful magnetic fields, are also known to exist.

#### Types of magnets

##### Electromagnets

Electromagnets are useful in cases where a magnet must be switched on or off for instance, large There was an error working with the wiki: Code[16]s to lift junked automobiles.

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 There was an error working with the wiki: Code[73] of wire is formed such that the current is traveling in a There was an error working with the wiki: Code[74], then all of the field lines in the center of the loop are directed in the same direction, resulting in a magnetic There was an error working with the wiki: Code[75] 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.

##### Magnetic metallic elements

Many materials have unpaired electron spins, but the majority of these materials are There was an error working with the wiki: Code[76]. When the spins interact with each other in such a way that the spins align spontaneously, the materials are called There was an error working with the wiki: Code[77] (what is often loosely termed "magnetic"). Due to the way their regular There was an error working with the wiki: Code[78] There was an error working with the wiki: Code[79] causes their spins to interact, some There was an error working with the wiki: Code[80]s are (ferro)magnetic when found in their natural states, as There was an error working with the wiki: Code[81]s. These include There was an error working with the wiki: Code[82] (There was an error working with the wiki: Code[83] or There was an error working with the wiki: Code[84]), There was an error working with the wiki: Code[85], and There was an error working with the wiki: Code[86], as well the rare earth metals There was an error working with the wiki: Code[87] and There was an error working with the wiki: Code[88] (when at a very low temperature). Such naturally occurring (ferro)magnets were used in the first experiments with magnetism. Technology has expanded the availability of magnetic materials to include various manmade products, all based, however, on naturally magnetic elements.

##### Ceramic or ferrite

Ceramic, or ferrite, magnets are made of a There was an error working with the wiki: Code[17] of powdered iron oxide and barium/strontium carbonate There was an error working with the wiki: Code[89]. Due to the low cost of the materials and manufacturing methods, inexpensive magnets (or nonmagnetized ferromagnetic cores, for use in There was an error working with the wiki: Code[90] such as There was an error working with the wiki: Code[91], for example) of various shapes can be easily mass produced. The resulting magnets are noncorroding, but There was an error working with the wiki: Code[92] and must be treated like other ceramics.

##### Alnico

Alnico magnets are made by There was an error working with the wiki: Code[93] or There was an error working with the wiki: Code[94] a combination of There was an error working with the wiki: Code[95], nickel and cobalt with iron and small amounts of other elements added to enhance the properties of the magnet. Sintering offers superior mechanical characteristics, whereas casting delivers higher magnetic fields and allows for the design of intricate shapes. Alnico magnets resist corrosion and have physical properties more forgiving than ferrite, but not quite as desirable as a metal.

##### Injection molded

There was an error working with the wiki: Code[18] magnets are a There was an error working with the wiki: Code[96] of various types of There was an error working with the wiki: Code[97] and magnetic powders, allowing parts of complex shapes to be manufactured by injection molding. The physical and magnetic properties of the product depend on the raw materials, but are generally lower in magnetic strength and resemble There was an error working with the wiki: Code[98]s in their physical properties.

##### Flexible

Flexible magnets are similar to injection molded magnets, using a flexible resin or binder such as There was an error working with the wiki: Code[99], and produced in flat strips or sheets. These magnets are lower in magnetic strength but can be very flexible, depending on the binder used.

##### Rare earth magnets

'Rare earth' (There was an error working with the wiki: Code[100]) elements have a partially occupied f There was an error working with the wiki: Code[101] (which can accommodate up to 14 electrons.) The spin of these electrons can be aligned, resulting in very strong magnetic fields, and therefore these elements are used in compact high-strength magnets where their higher price is not a factor.

##### Samarium cobalt

Samarium cobalt magnets are highly resistant to oxidation, with higher magnetic strength and temperature resistance than alnico or ceramic materials. Sintered samarium cobalt magnets are brittle and prone to chipping and cracking and may fracture when subjected to thermal shock.

##### Neodymium iron boron (NIB)

There was an error working with the wiki: Code[102], more formally referred to as neodymium iron boron (NdFeB) magnets, have the highest magnetic field strength, but are inferior to samarium cobalt in resistance to oxidation and temperature. This type of magnet is expensive, due to both the cost of raw materials and licensing of the patents involved. This high cost limits their use to applications where such high strengths from a compact magnet are critical. Use of protective surface treatments such as gold, nickel, zinc and tin plating and epoxy resin coating can provide There was an error working with the wiki: Code[103] protection where required.

##### Single-molecule magnets (SMMs) and single-chain magnets (SCMs)

In the There was an error working with the wiki: Code[104] it was discovered that certain molecules containing paramagnetic metal ions are capable of storing a magnetic moment at very low temperatures. These are very different from conventional magnets that store information at a "domain" level and theoretically could provide a far denser storage medium than conventional magnets. In this direction research on monolayers of SMMs is currently under way. Very briefly, the two main attributes of an SMM are:

# a large ground state spin value (S), which is provided by There was an error working with the wiki: Code[105] or There was an error working with the wiki: Code[106] coupling between the paramagnetic metal centres.

# a negative value of the anisotropy of the zero field splitting (D)

Most SMM's contain manganese, but can also be found with vanadium, iron, nickel and cobalt clusters.

More recently it has been found that some chain systems can also display a magnetization which persists for long times at relatively higher temperatures. These systems have been called single-chain magnets.

##### Nano-structured magnets

Some nano-structured materials exhibit energy There was an error working with the wiki: Code[107]s called There was an error working with the wiki: Code[108]s that coalesce into a common ground state in the manner of a There was an error working with the wiki: Code[109].

#### Units of electromagnetism

##### SI magnetism units

{|

|+ style="font-size:largerfont-weight:bold"|SI&nbspElectromagnetism units There was an error working with the wiki: Code[2]

|-

!Symbol

!Name of Quantity

!Derived Units

!Unit

!Base Units

|-

| I

| There was an error working with the wiki: Code[19])

| A

| A = W/V = C/s

|-

| q

| Electric charge, There was an error working with the wiki: Code[110]

| There was an error working with the wiki: Code[111]

| C

| A·s

|-

| V

| There was an error working with the wiki: Code[112]

| Volt

| V

| J/C = kg·m2·s&minus3·A&minus1

|-

| R, Z, X

| Electrical resistance, There was an error working with the wiki: Code[113], There was an error working with the wiki: Code[114]

| There was an error working with the wiki: Code[20]

| &Omega

| V/A = kg·m2·s&minus3·A&minus2

|-

| &rho

| There was an error working with the wiki: Code[21]

| There was an error working with the wiki: Code[22] Metre

| &Omega·m

| kg·m3·s&minus3·A&minus2

|-

| P

| Watt

| W

| V·A = kg·m2·s&minus3

|-

| C

| There was an error working with the wiki: Code[115]

| There was an error working with the wiki: Code[116]

| F

| q/V = kg&minus1·m&minus2·A2·s4

|-

|

| There was an error working with the wiki: Code[23]

| reciprocal There was an error working with the wiki: Code[117]

| F&minus1

| V/C = kg·m2·A&minus2·s&minus4

|-

| &epsilon

| There was an error working with the wiki: Code[118]

| There was an error working with the wiki: Code[119] per Metre

| F/m

| kg&minus1·m&minus3·A2·s4

|-

| &chie

| There was an error working with the wiki: Code[120]

| (dimensionless)

| -

| -

|-

| G, Y, B

| There was an error working with the wiki: Code[24], There was an error working with the wiki: Code[121], There was an error working with the wiki: Code[122]

| There was an error working with the wiki: Code[25]

| S

| &Omega&minus1 = kg&minus1·m&minus2·s3·A2

|-

| &sigma

| There was an error working with the wiki: Code[26]

| There was an error working with the wiki: Code[27] per Metre

| S/m

| kg&minus1·m&minus3·s3·A2

|-

| H

| Ampere per Metre

| A/m

| A·m&minus1

|-

| &Phim

| There was an error working with the wiki: Code[123]

| There was an error working with the wiki: Code[28]

| Wb

| V·s = kg·m2·s&minus2·A&minus1

|-

| B

| There was an error working with the wiki: Code[29]

| T

| Wb/m2 = kg·s&minus2·A&minus1

|-

|

| There was an error working with the wiki: Code[124]

| There was an error working with the wiki: Code[30]

| A/Wb

| kg&minus1·m&minus2·s2·A2

|-

| L

| There was an error working with the wiki: Code[125]

| There was an error working with the wiki: Code[31]

| H

| Wb/A = V·s/A = kg·m2·s&minus2·A&minus2

|-

| &mu

| There was an error working with the wiki: Code[32]

| There was an error working with the wiki: Code[33] per Metre

| H/m

| kg·m·s&minus2·A&minus2

|-

| &chim

| There was an error working with the wiki: Code[126]

| (dimensionless)

| -

| -

|}

##### Other magnetism units

There was an error working with the wiki: Code[34]-The gauss, abbreviated as G, is the There was an error working with the wiki: Code[35] of There was an error working with the wiki: Code[127] or There was an error working with the wiki: Code[128] (B).

There was an error working with the wiki: Code[36] of There was an error working with the wiki: Code[129].

There was an error working with the wiki: Code[37]-is the unit for the There was an error working with the wiki: Code[130].

#### Related concepts

Electrostatics

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Electromagnetism

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Magnetic field

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#### References and external articles

Griffiths, David J. Introduction to Electrodynamics (3rd ed.) Prentice Hall 1998 ISBN 0-13-805326-X}}

Tipler, Paul Physics for Scientists and Engineers: Electricity, Magnetism, Light, and Elementary Modern Physics (5th ed.) W. H. Freeman 2004 ISBN 0-7167-0810-8

There was an error working with the wiki: Code[1], Wikipedia: The Free Encyclopedia. Wikimedia Foundation.

On the Magnet, 1600 First scientific book on magnetism by the father of electrical engineering. Full English text, full text search.

http://www.wondermagnet.com/magfaq.html Info on electromagnetism and homemade projects & experiments.

http://www.magnetostatics.us/photo.htm - Real images of magnetic flux.

http://www.scientiapress.com/trbc/trbc.htm Theory of the There was an error working with the wiki: Code[141] (they fit 19 criteria for the animal magnetoreceptor).

http://www.rare-earth-magnets.com/magnet_university/magnet_university.htm Resources from the fundamental theory of magnetism to advanced applications of magnetic materials.

Nanomagnets Bend The Rules

Nanomagnets bend the rules