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Difference Between EMF and MMF

Difference Between Electromotive Force and Magnetomotive Force

What is Magnetomotive Force (MMF)?

The pressure required to establish magnetic flux is a ferromagnetic material (material having permeabilities hundreds and thousands time greater than of free space) is known as magnetomotive force (MMF). It is measured in ampere-turns.

When current flow through a conductor coil, a force has been produced which drives magnetic lines or flux which is know magnetomotive force or MMF. In other words, a pressure which drives the gametic flux from north pole to the south pole is called MMF (Magnetomotive force).

In short, a force which is responsible to drive flux in the magnetic circuit (same as electromotive (EMF) which drives electron in an electric circuit)  is known as magnetomotive force .

The SI unit of MMF is AT (Ampere-Turns) and G (Gilbert) is the CGS unit of magnetomotive force. It is also known as Ohm’s law for magnetic circuits which can be expressed as:

ℱ = ΦR


F = Hl


F = NI


  • F or ℱ = Magnetomotive force
  • Φ = Magnetic flux
  • R = Reluctance (magnetic resistance) of the circuit
  • H = Magnetizing force (strength of magnetizing field)
  • l = Mean length of solenoid
  • I = Current
  • N = Numbers of coil turns

Related Post: Difference Between Electric and Magnetic Circuit

What is Electromotive Force (EMF)?

EMF is the cause and voltage is the effect. Electromotive force (EMF) produces and maintains potential difference or voltage inside an active cell. EMF supplies energy in joules to each unit of coulomb charge. The symbol of EMF is E or ε and the SI unit of electromotive force is V (Volt) same as for voltage.

EMF can be expressed by the following equation:

ε or E = W/Q … in Volts


  • ε or E = Electromotive force in volts
  • W = Work done in joules
  • Q = Charge in Columbus

Related Post: Difference Between Voltage and EMF?

Difference Between EMF and MMF (Electromotive Force and Magnetomotive Force)

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