In this topic, you study Magnetomotive Force (MMF) – Definition & Theory.
We know that in an electric circuit, electric current is due to the presence of an electromotive force. Similarly, in the magnetic circuit, it can be said that the magnetic flux is due to the presence of magnetomotive force. This magnetomotive force which produces or tends to produce the flux in the magnetic circuit is given by the product of turns on the magnetizing coil (N) and the current flowing in the coil (I) in amperes i.e.
M.M.F. N I amperes
The value of m.m.f. is descriptively expressed in ampere turns. But N being a dimensionless number, unit for magnetomotive force is ampere (A) However, an ampere of m.m.f. is quite different from the current ampere.
The magnetomotive force is usually defined as the work done in joules on a unit magnetic pole in taking it once round a closed magnetic circuit.
Reluctance (S):