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Magnetism is the class of physical attributes that occur through a magnetic field, which allows objects to attract or repel each other. Because both electric currents and magnetic moments of elementary particles give rise to a magnetic field, magnetism is one of two aspects of electromagnetism .
The American Physical Society and the American Association of Physics Teachers recommend a full year of graduate study in electromagnetism for all physics graduate students. [4] A joint task force by those organizations in 2006 found that in 76 of the 80 US physics departments surveyed, a course using John Jackson 's Classical Electrodynamics ...
In three dimensions, the derivative has a special structure allowing the introduction of a cross product: = + = + from which it is easily seen that Gauss's law is the scalar part, the Ampère–Maxwell law is the vector part, Faraday's law is the pseudovector part, and Gauss's law for magnetism is the pseudoscalar part of the equation.
[55]: 64 In this model, a magnetic H-field is produced by magnetic poles and magnetism is due to small pairs of north–south magnetic poles. Three discoveries in 1820 challenged this foundation of magnetism. Hans Christian Ørsted demonstrated that a current-carrying wire is surrounded by a circular magnetic field.
Rather than "magnetic charges", the basic entity for magnetism is the magnetic dipole. (If monopoles were ever found, the law would have to be modified, as elaborated below.) Gauss's law for magnetism can be written in two forms, a differential form and an integral form. These forms are equivalent due to the divergence theorem.
In classical electromagnetism, magnetization is the vector field that expresses the density of permanent or induced magnetic dipole moments in a magnetic material. Accordingly, physicists and engineers usually define magnetization as the quantity of magnetic moment per unit volume. [1]
This page lists examples of magnetic induction B in teslas and gauss produced by various sources, grouped by orders of magnitude.. The magnetic flux density does not measure how strong a magnetic field is, but only how strong the magnetic flux is in a given point or at a given distance (usually right above the magnet's surface).
Magnetic domain theory was developed by French physicist Pierre-Ernest Weiss [1] who, in 1906, suggested existence of magnetic domains in ferromagnets. [2] He suggested that large number of atomic magnetic moments (typically 10 12-10 18) [citation needed] were aligned parallel.