- Magnetomotive force
Conventional Magnetic Circuits
Phasor Magnetic Circuits
Gyrator-capacitor model variables
Magnetomotive force (MMF) (SI Unit: Ampere) is any physical driving (motive) force that produces magnetic flux. In this context, the expression "driving force" is used in a general sense of "work potential", and is analogous, but distinct from force measured in newtons. The name came about because in magnetic circuits it plays a role analogous to the role electromotive force (voltage) plays in electric circuits.
SI versus CGS units
The CGS unit of magnetomotive force is the gilbert (Gi), established by the IEC in 1930 . The gilbert is defined differently, and is a slightly smaller unit than the ampere. The unit is named after William Gilbert (1544–1603) English physician, astronomer and natural philosopher.
The conversion factor between the SI and CGS units is (≈ 0.795774715) ampere for every gilbert.
where N is the number of turns of wire in the coil and I is the current in the wire.
The equation for the magnetic flux in a magnetic circuit, sometimes known as Hopkinson's law, is:
where Φ is the magnetic flux and is the reluctance of the magnetic circuit. It can be seen that the magnetomotive force plays a role in this equation analogous to the voltage V in Ohm's law: V = IR.
- The Penguin Dictionary of Physics, 1977, ISBN 0-14-051071-0
Wikimedia Foundation. 2010.