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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 ...
For many paramagnetic materials, the magnetization of the material is directly proportional to an applied magnetic field, for sufficiently high temperatures and small fields.
[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 physics, fields are entities that interact with matter and can be described mathematically by assigning a value to each point in space and time. Vector fields are fields which are assigned both a numerical value and a direction at each point in space and time. Electric charges produce a vector field called the electric field. The numerical ...
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]
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.