Magnetomotive Force


Magnetomotive Force (MMF) is a measure of the magnetic force generated by an electric current flowing through a coil or wire. It is responsible for creating magnetization in a magnetic material and establishing a magnetic field around a current-carrying conductor. The strength of MMF is directly proportional to the current flowing through the conductor and the number of turns in the coil.

Key Takeaways

  1. Magnetomotive Force (MMF) is the force that drives a magnetic flux through a magnetic circuit, similar to the electromotive force that drives an electric current in an electrical circuit.
  2. MMF is measured in ampere-turns (AT) and is calculated by multiplying the current flowing through a coil by the number of turns in that coil. A higher current or more turns of the coil result in a stronger magnetomotive force.
  3. Magnetomotive Force directly affects the inductance and magnetic field strength of an inductor or coil, making it a crucial factor in designing and analyzing magnetic circuits and devices, such as transformers, solenoids, and motors.


Magnetomotive force (MMF) is an important term in technology as it refers to the force that drives the flow of magnetic flux in an electrical circuit or device, which in turn generates the magnetic field.

The strength of the generated magnetic field is directly proportional to the MMF, making it a vital component in the design and functioning of various electrical devices, such as motors, transformers, and solenoids.

Understanding and controlling MMF allows engineers to optimize the performance and efficiency of these devices, leading to improved power distribution, energy consumption, and device reliability.

Therefore, magnetomotive force is an essential concept in electrical engineering and technology.


Magnetomotive Force (MMF) serves a significant purpose in the realm of electromagnetism and its practical applications. Primarily, MMF is responsible for driving the magnetic flux through a magnetic circuit, much like electromotive force pushes electric current in an electrical circuit. One of the primary applications of magnetomotive force is found in electric motors and generators.

In such devices, MMF enables the conversion of electrical energy to mechanical energy or vice versa, thereby facilitating movement, rotation, or generation of electricity as needed. Moreover, the understanding and utilization of magnetomotive force have spurred advancements in various other fields, such as telecommunications, medical diagnostics, and industrial processes. In the case of transformers, MMF drives magnetic fields through coil windings, allowing the efficient transfer of electrical energy between circuits without a direct electrical connection.

This fundamental concept is essential for high-voltage power transmission and distribution in modern electrical grids. Similarly, the use of magnetomotive force in magnetic resonance imaging (MRI) machines enables the production of detailed images of internal body structures for diagnostic purposes. Overall, magnetomotive force is a key element for harnessing, controlling, and manipulating magnetic fields to achieve desired outcomes across diverse applications and industries.

Examples of Magnetomotive Force

Magnetomotive Force (MMF) is a measure of the magnetic force that drives the flow of magnetic flux in a magnetic circuit. It is analogous to the electromotive force in electrical circuits. Here are three real-world examples where magnetomotive force is relevant:

Electric motors: In electric motors, MMF is responsible for creating the magnetic field that causes the motor’s rotor to spin. When current flows through the motor’s windings, it generates MMF, which in turn produces a magnetic field. This magnetic field interacts with the rotor’s magnetic field, causing rotation and ultimately driving the motor.

Transformers: Transformers are devices that transfer electrical energy between two circuits at different voltage levels through electromagnetic induction. MMF plays a crucial role in transformers’ functioning, as it creates the magnetic flux in the transformer’s core. As a current passes through the primary coil, it generates MMF, leading to a magnetic field in the core. This field induces an electromotive force in the secondary coil, transferring the energy to the other circuit.

Magnetic levitation trains (Maglev): Maglev trains use MMF for their levitation and propulsion systems. These trains rely on powerful magnets to create magnetic fields, allowing them to float above the guideway, which is lined with electromagnets. MMF drives the magnetic fields that generate the necessary lift and propulsion forces for the train to levitate, move forward, and maintain stability.

Frequently Asked Questions: Magnetomotive Force

1. What is magnetomotive force?

Magnetomotive force (MMF) is the force that generates magnetic field in an electric circuit. It’s expressed as the product of the number of turns in a coil and the current flowing through it. This force is responsible for the creation of a magnetic field that surrounds the conductor.

2. How is magnetomotive force calculated?

Magnetomotive force is calculated using the formula: MMF = NI, where N is the number of turns in the coil, and I is the current flowing through the coil. It is typically measured in Ampere-turns (At).

3. What is the difference between magnetomotive force and magnetic field strength?

Magnetomotive force is the force that generates a magnetic field, while magnetic field strength is a measure of the intensity of the magnetic field produced. In other words, MMF is the cause and magnetic field strength is the effect. Magnetic field strength is measured in oersteds (Oe) in the CGS system or amperes per meter (A/m) in the SI system.

4. How does magnetomotive force relate to electromagnets?

In electromagnets, magnetomotive force is the driving force that creates a magnetic field around the coil. When an electrical current flows through the coil, this generates MMF, which in turn, creates a magnetic field. The strength of an electromagnet can be controlled by adjusting the MMF, which can be done by changing the number of turns in the coil or the current passing through it.

5. Can magnetomotive force be changed in a circuit?

Yes, magnetomotive force can be changed in a circuit by altering parameters like the number of turns in the coil or the current flowing through it. By increasing the current or the number of turns, you can increase the MMF and vice versa. This, in turn, affects the strength of the magnetic field produced around the circuit.

Related Technology Terms

  • Electromagnetism
  • Coil winding
  • Magnetic field strength
  • Magnetic flux
  • Reluctance

Sources for More Information


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