In physics, the **Magneto Motive Force (MMF)** is a quantity appearing in the equation for the magnetic flux in a magnetic circuit, sometimes known as Hopkinson's law:

where *Φ* is the magnetic flux and *R* is the magnetic reluctance of the 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*.

Magnetomotive force is the thought to be the same as electromotive force, emf (= difference in electric potential, or voltage, between the terminals of a source of electricity, e.g., a battery from which no current is being drawn) since it is the cause of magnetic flux in a magnetic circuit; i.e.,

*ℱ*=*NI*- where
*N*is the number of turns in the coil and*I*is the electric current through the electrical circuit

- where
*ℱ*=*ΦR*- where
*Φ*is the magnetic flux and*R*is the magnetic reluctance

- where
*ℱ*=*HL*- where
*H*is the magnetizing force (the strength of the magnetizing field) and*L*is the mean length of a solenoid or the circumference of a toroid ring

- where

## References[]

*The Penguin Dictionary of Physics*, 1977, ISBN 0-14-051071-0*A textbook of Electrical Technology*, 2008, ISBN 81-219-2440-5