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*From*: "Folkerts, Timothy" <FolkertsT@BARTONCCC.EDU>*Date*: Fri, 13 Feb 2004 14:45:12 -0600

We, as physicists, often seem to be stuck with various conventions and

definitions. These conventions are often not the most convenient or most

logical, but once they get ingrained, they seem almost impossible to adjust.

Today's inconvenient convention is capacitance (and I bet I could come up

with one a day for the next month). There are two obvious ratios we could

consider:

C = Q/V

C' = V/Q

The first, of course, is the standard definition of capacitance, but the

second is much more logical because it then matches R & L:

1) similar definitions:

C' = V / Q

R = V / (dQ/dt)

L = V / (d2Q/dt2)

2) Similar geometry (at least for "standard" geometries):

C' = (1/e0) l/A (l = length; 1 = one)

R = (rho) l/A

L = (mu0 N^2) l/A

3) Similar addition rules:

For all three - in series, you simply add values

- in parallel, you add inverses.

I can't think of a single case where this definition is inferior (except, of

course, for historical inertia). Think of all the time and confusion we

could save our students. Now we just need to hire a good ad agency and/or

grease the palms of a few textbook editors ;-)

Tim Folkerts

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