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Magnetic forces are fundamental forces that arise due to the movement of electrical charge. Maxwell's equations describe the origin and behavior of the fields that govern these forces (see also the Biot-Savart Law). Thus, magnetism is seen whenever electrically charged particles are in motion. This can arise either from movement of electrons in an electric current, resulting in 'electromagnetism', or from the constant subatomic movement of electrons, resulting in what are known as 'permanent magnets'.
Normally, magnetic fields are seen as dipoleThis article is about the electromagnetic phenomenon. From the point of view of the mathematics of distributions, a dipole can be taken to be the directional derivative of a Dirac delta function. A dipole is also a type of radio antenna A dipole is a pairs, having a ' South pole' and a ' North pole'; terms dating back to the use of magnets as compassThis article is about the navigational tool. For other meanings, see Compass (disambiguation A compass (or mariner's compass is navigational instrument for finding directions. It consists of a magnetised pointer free to align itself accurately with Earth'es, interacting with the Earth's magnetic fieldThe cause of Earth's magnetic field (the surface magnetic field is not known for certain, but is possibly explained by dynamo theory. The magnetic field extends several tens of thousands of kilometres into space. The field is approximately a magnetic dipo to indicate North and South on the globe.
A magnetic field contains energyThis article is about the scientific concept. Energy use by humans is discussed in other articles''. Energy generally and qualitatively speaking, is the property (or the quantity of the property) of doing things or supplying power. The expressions energy, and physical systems will stabilize into the configuration with the lowest energy. Therefore, when placed in a magnetic field, a magnetic dipole will tend 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 minimum. For instance, two identical bar magnets will normally line up North to South resulting in no net magnetic field, and be resistant to 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 the magnet used as a compass will interact with the Earth's magnetic field to indicate North and South).
Contrary to normal experience, theoretical physics predicts the existence of Magnetic monopoles. Paul Dirac observed in 1931 that, because electrical theory and magnetic theory 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. In practice, however, although charged particles like protons and electrons can be easily isolated as individual electrical charges, magnetic south and north poles do not appear in isolation. Using quantum theory Dirac showed that if magnetic monopoles exist, then one could explain why the observed elementary particles carry charges that are integral multiples of the charge of the electron. Quarks carry fractional electric charge, but they do not appear as free particles.
In modern elementary particle theory, the "quantization" of charge is realised in a spontaneous breakdown of a non-abelian gauge symmetry. It should be noted that the monopoles predicted in certain Grand unified theories are different from the one originally thought of by Dirac. These monopoles, unlike that of elementary particles are solitons , namely localised energy packets. These monopoles, if at all they exist, contradict cosmological observations. A solution to this monopole problem in Cosmology gave rise to the currently interesting idea of inflation.