The crucial difference between the electric field and the magnetic field is the absence of magnetic monopoles. In electrostatics a positive charge can exist on its own, separate from a negative one; in magnetism this never happens.
Magnetic monopoles do not exist
In nature isolated magnetic charges are never found. Every magnet always has two poles, North (N) and South (S): if you split a magnet in half you do not get “half N” and “half S” separately, but two smaller magnets, each with its own N and S.
Splitting a magnet does not separate the poles: it duplicates them. However finely you keep cutting, you always get complete dipoles, never a single pole.
Splitting a magnet gives two complete magnets, not two isolated monopoles.
The mathematical consequence is clear-cut: the flux of through any closed surface is always zero. Every line that enters a volume also leaves it, because there are no magnetic “sources” inside for them to terminate on.
Zero magnetic flux
This is the magnetic analogue of Gauss’s theorem, but with the enclosed charge always zero. This law will become one of Maxwell’s four equations.
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Topics: Magnetismo Concepts: Campo magnetico · Flusso magnetico
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