Difference between Fm and H

Question

What's the difference between magnetomotive force(MMF)(Fm) and magnetizing force (the strength of the magnetizing field)(H) ?

H=F/l per unit length, l [m] – Tony Stewart EE75 Dec 05 '16 at 17:18 — Tony Stewart EE75, Dec 05 '16 at 17:18

score 0 · Answer 1 · answered Dec 05 '16 at 17:18

0

H (magnetising force) is in units of amps per metre.

F (magnetomotive force) is in units of amps.

Apart from the per distance thing, they are essentially the same thing.

answered Dec 05 '16 at 17:18

Neil_UK

166,079
3
185
408

score 0 · Answer 2 · answered Dec 05 '16 at 18:33

Magnetic field strength (H with units of ampere (turns) per metre) is the intensity of a magnetic field just as electric field strength (E in volts per metre) is an intensity of an electric field. Both (H and E) are the fields that create an electromagnetic field.

MMF is just ampere (turns) and so is not a field quantity.

H gives rise to magnetic flux density via the magnetic permeability of the material it is associated with. You cannot calculate flux density with MMF alone - you need a material specification (iron, ferrite, air etc.) and a path length.

Difference between Fm and H

2 Answers2