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Re: coulombs and amps

A major 19th century industry was electroplating. If you know
some chemistry and valence stuff, you can relate the amount of material
deposited to the amount of charge carried. This led to an early definition

Modern SI defn of an Ampere: ...that constant current which, if
maintained in two straight parallel conductors of infinite length, of
negligable circular cross section and placed 1 meter apart in a vacuum, would
produce between these conductors a force equal to 2 x 10^-7 newton per meter
of length. [9th CGPM (1948), Resolutions 2 and 7.]

In SI, Coulomb is a derived unit: ...quantity of electricity carried in one
second by a current of one ampere;

Cohen, E.R. (1995). The physics quick reference guide. Woodbury NY: AIP Press.
p. 17 & 21.

yah, the original Coulomb WAS defined through electrochemistry. Looks like
the modern fundamental/derived units in SI are a little backwards due to
measurement techniques. Committees decide these things, so no surprise :^)

Dan, who is on too many committees himself

Dan MacIsaac, Assistant Professor of Physics and Astronomy, Northern AZ Univ