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Today I had a discussion with a colleague who teaches electricity and magnetism to 2nd year undergraduate physics students. He is seeking the best way to explain how is the emf generated inside a battery with a minimal appeal to physics beyond classical. We have lamented that some textbooks refer to "non-electromagnetic chemical forces" since all of chemistry is essentially electrostatics+quantum mechanics.

Our proposal is to draw the students' attention to the existence of atoms which can not be explained by classical mechanics + classical electromagnetism. In the same vein the forces on charge carriers in galvanic cells are electromagnetic but the response is not classical. Thus a battery "amplifies" non-classicality to the level macroscopic electricity. It is not that forces are non electrostatic but the systems response is not classical. Can you recommend textbooks or online sources that use/expand this idea?

(the main tag for this question should be "teaching" but I'm too much of a rookie here to create one)

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thanks! Missed "education" tag somehow –  Slaviks Aug 17 '11 at 19:45
Slaviks, I'll give you some points for your answer to my question on color tracking. You'll be creating all the tags you want before long. –  Marty Green Aug 18 '11 at 0:21

2 Answers 2

up vote 2 down vote accepted

What you're describing is electrochemistry, which is summarised here as

Electrochemistry is a branch of chemistry that studies chemical reactions which take place in a solution at the interface of an electron conductor (a metal or a semiconductor) and an ionic conductor (the electrolyte), and which involve electron transfer between the electrode and the electrolyte or species in solution.

You don't need to delve into quantum mechanics to understand what's going on at the macro level since this branch of science has been around since Faraday, and so basic chemistry will suffice. On the other hand, the inner workings of chemistry are down to non-relativistic quantum mechanics and the solution of Schrodinger's equation which determines how electrons behave within atoms and with other electrons. Here's a link that develops a classical picture of the physical processes involved which is easily accessible to your students:


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"Chemestry" indeed is a good link here. So we would say that producing emf in a cell requires "chemical forces" which are electrostatics acting at the molecular (hence, quantum) level. –  Slaviks Aug 17 '11 at 20:00

Each chemical species has a specific strength of oxidation and/or reduction. The Redox potential is what chemists use to calculate the electrode potential of a battery:

E°cell = E°red(cathode) – E°red(anode) = E°red(cathode) + E°oxi(anode)

Wikipedia has a nice compilation of Redox potentials, which are used in the above formula to calculate the voltage produced by a electrochemical cell.

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