Magnetomotive Force
Definition: Just as an electromotive force (EMF) is required to drive electric current in an electrical circuit, a magnetomotive force (MMF) is necessary to establish magnetic flux in a magnetic circuit. MMF is the magnetic "pressure" that generates and sustains magnetic flux. The SI unit of MMF is the ampere-turn (AT), while its CGS unit is the gilbert (G). For the inductive coil depicted in the figure below, the MMF can be expressed as:
Where:
N = number of turns of the inductive coil I = current
The strength of the MMF is equal to the product of the current flowing through the coil and the number of turns. According to the work law, MMF is defined as the work done to move a unit magnetic pole (1 weber) once around the magnetic circuit.MMF is also referred to as magnetic potential—a property of a material that generates a magnetic field. It is the product of magnetic flux Φ and magnetic reluctance R. Reluctance is the opposition offered by a magnetic circuit to the establishment of magnetic flux. Mathematically, MMF in terms of reluctance and magnetic flux is expressed as:
