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MMF is most familiar to us as magnetism. The physical force that you feel between magnets is called MMF, or ‘magnetomotive force’. A less familiar manifestation occurs when two wires with electric current passing through them are placed near to each other. A physical force exists between them. (It’s usually too small to feel but the effect is exploited in electric motors.) An MMF is a result of a magnetic field, and the study of magnetic fields is called electromagnetics, which we won’t get involved in here.

If we were to make the wires a given length and separate them by a given distance we could increase the current until we had some given measurable force. Then we would have a unit value of electrical current, the ampere or amp. The amp is abbreviated to A. The symbol which we use for electrical current in equations is I.

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Excerpt from: “Electronics Calculations Data Handbook” by Daniel McBrearty. Scribd.