Definition
The force that drives magnetic flux through a magnetic circuit, produced by current flowing through a coil of wire. Its strength is measured in ampere-turns and is determined by the amount of current multiplied by the number of turns in the coil.
Plain English
The push that creates and moves a magnetic field. The more current you send through a coil, and the more loops of wire that coil has, the stronger the magnetic push.
Context Anchor
Seen in aircraft electrical system theory when studying generators, alternators, motors, relays, solenoids, and other devices that use electromagnetism.
Derivation
From 'magneto-' (relating to magnetism) and 'motive force' (something that causes motion). The term was coined to parallel 'electromotive force' (voltage), which drives electric current. Just as voltage pushes current through a wire, magnetomotive force pushes magnetic flux through iron and air.
Why Pilots Care
Many aircraft components — starter motors, generators, relays, solenoids, and gyro instruments — rely on magnetomotive force to function. Understanding it helps make sense of how electrical equipment produces motion or magnetic effects in the aircraft.
Analogy
Think of it like water pressure in a hose. Voltage pushes electrons through wires; magnetomotive force pushes magnetic flux through a magnetic circuit. More current and more coil turns means more 'pressure' driving the magnetism.
Intuition Check
Do not read “force” here as a physical shove you can feel with your hand. In this term, it means the cause that sets up a magnetic field.
Example Sentence 1
The magnetomotive force in the starter solenoid pulls the plunger in and closes the heavy contacts that crank the engine.
Example Sentence 2
A stronger magnet increases the magnetomotive force available in the ignition system.