Electromotive Force Definition (EMF)

What Is Electromotive Force?

Small transformer coil on desk
A transformer coil generates electromotive force or emf.

FroggyFrogg, Getty Images
By
Anne Marie Helmenstine, Ph.D.
Anne Marie Helmenstine, Ph.D.
Chemistry Expert
  • Ph.D., Biomedical Sciences, University of Tennessee at Knoxville
  • B.A., Physics and Mathematics, Hastings College
Dr. Helmenstine holds a Ph.D. in biomedical sciences and is a science writer, educator, and consultant. She has taught science courses at the high school, college, and graduate levels.
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Updated on July 10, 2019
EMF is the net voltage of half-reactions in an electrochemical cell.
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Electrochemical Cell EMF Example Problem
By Todd Helmenstine

Electromotive force is the electric potential generated by either a electrochemical cell or a changing magnetic field. It is also known as voltage. It is electrical action produced by a non-electrical source, such as a battery (converts chemical energy to electrical energy) or generator (converts mechanical energy into electrical energy). Although the term contains the word "force" it's not akin to a force in physics that would be measured in newtons or pounds.
Electromotive force is commonly denoted by the acronym emf, EMF or a cursive letter E.
The SI unit for electromotive force is the volt.

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Helmenstine, Anne Marie, Ph.D. "Electromotive Force Definition (EMF)." ThoughtCo, Feb. 16, 2021, thoughtco.com/definition-of-electromotive-force-605070. Helmenstine, Anne Marie, Ph.D. (2021, February 16). Electromotive Force Definition (EMF). Retrieved from https://www.thoughtco.com/definition-of-electromotive-force-605070 Helmenstine, Anne Marie, Ph.D. "Electromotive Force Definition (EMF)." ThoughtCo. https://www.thoughtco.com/definition-of-electromotive-force-605070 (accessed April 16, 2024).