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flux, magnetic,in physics, term used to describe the total amount of magnetic fieldfield,
in physics, region throughout which a force may be exerted; examples are the gravitational, electric, and magnetic fields that surround, respectively, masses, electric charges, and magnets. The field concept was developed by M.
..... Click the link for more information. in a given region. The term flux was chosen because the power of a magnet seems to "flow" out of the magnet at one pole and return at the other pole in a circulating pattern, as suggested by the patterns formed by iron filings sprinkled on a paper placed over a magnet or a conductor carrying an electric current. These patterns are called lines of induction. Although there is no actual physical flow, the lines of induction suggest the correct mathematical description of magnetism in terms of a field of force. The lines of induction originate on the north pole of the magnet and end on the south pole; their direction at any point is the direction of the magnetic field, and their density (the number of lines passing through a unit area) gives the strength of the field. Near the poles where the lines converge, the field and the force it produces are large; away from the poles where the lines diverge, the field and force are progressively weaker.
the flux Φ of the vector of magnetic induction B through a surface. The magnetic flux dΦ through a small area dS within which the vector B can be considered constant is expressed by the product of the area and the projection Bn of the vector onto the normal to the area, that is, by dΦ = BndS. The magnetic flux Φ through a finite surface S is defined by the integral
Ф = ∫S Bn dS
For a closed surface, this integral is equal to zero, reflecting the solenoidal character of a magnetic field, that is, the absence in nature of magnetic charges—the sources of a magnetic field. The unit of magnetic flux in the International System of Units is the weber, and in the cgs system, the maxwell (1 weber = 108 maxwells).