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:

Where:

• R = reluctance

• Φ = magnetic flux

The magnetomotive force (MMF) can also be expressed in terms of the magnetic field intensity (H) and the length (l) of the magnetic path. Magnetic field intensity represents the force exerted on a unit magnetic pole within the magnetic field. The relationship is given by:

The magnetomotive force (MMF) can also be characterized in terms of the magnetic field intensity (H) and the length (l) of the magnetic path. The magnetic field intensity denotes the force exerted on a unit magnetic pole situated within the magnetic field. In this context, MMF is expressed as:

Where H is the magnetic field strength, and l is the length of the substance.