Basic Features of Magnetic Fields

Similar to the electric field, the magnetic field is a vector field continuously distributed in a certain space area. The basic physical quantity describing the magnetic field is the magnetic induction intensity vector B, which can also be represented visually by the magnetic field line. However, as a vector field, a magnetic field behaves quite differently from an electric field.

The magnetic field generated by the moving electric charge or the changing electric field, or the total magnetic field of the sum of the two, is a passive and rotating vector field, and the magnetic field lines are closed curve clusters that do not break or cross. In other words, in the magnetic field, there is no source that emits the magnetic field lines, nor does there exist a tail where the magnetic field lines converge. The closure of the magnetic field lines indicates that the loop integral along the magnetic field lines is not zero, that is, the magnetic field is a swirl field rather than a potential field (conservative field), and no There are scalar functions like electric potential.

In quantum mechanics, scientists believe that pure magnetic fields (and pure electric fields) are the effects of virtual photons. Expressed in Standard Model terms, photons are the medium through which all electromagnetic effects manifest. At low field energy conditions, the difference is negligible.