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Re: H2O vs. Wiedemann-Franz

At 11:14 AM 8/13/99 -0600, Jim Green wrote:
A college physics student asks the following question:

How can water be both a good thermal insulator and a good electrical
conductor?

An excellent question.

Answer: It can't. Compared to a metal, water is a relatively poor
conductor of heat -- but it is also a very poor conductor of electricity.

Think about the Wiedemann-Franz law, which is derived from the principle
that whatever carries charge also carries entropy. An electrical
nonconductor can always carry *additional* entropy by other channels, but
it's real hard to carry less than 1.5k of entropy per electron. (I said
"real hard" not "impossible" -- the big exception being superconductors --
but that's getting pretty far beyond the question that was asked.)