2.01 The magnetic circuit.

Magnets possess a magneto-motive force (m.m.f.). This m.m.f. generates magnetic flux, which forms a magnetic field surrounding the magnet, between its north and south poles .
Note: We say that the magnetic flux flows from the north to the south pole of a magnet. (This is shown by the arrows on the field lines). However, it is important to point out, that in fact, there is nothing actually flowing in the flux. We refer to the flux as flowing from the north to the south pole, to emphasise the directional properties of magnetic field lines. These directional properties are most apparent in the study of electromagnetism and electromagnetic induction.
Magnetic flux can exist in a vacuum or within in a medium, e.g. the air surrounding the magnet, or any other material within the path of the flux. The complete path through which the magnetic flux passes between the north and south pole is referred to as a magnetic circuit. The amount of flux produced by a magnet will depend, among other things. on the material within the magnetic circuit. i.e. Some materials have a greater reluctance to magnetic flux than others.

magnetic circuit
  • The magnet possesses a magneto motive force.
  • The m.m.f generates a magnetic flux.
  • The flux exists within the magnet and the air gap between the poles. The enclosed flux path is called a magnetic circuit.
  • A stronger m.m.f. will produce more flux.
  • The lower the reluctance of the magnetic circuit, the more flux will be produced.

Flux = magnetising force divided by reluctance

Note: The seemingly unusual units of ampere turns, is explained in electromagnetic theory