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*From*: Bernard Cleyet <anngeorg@PACBELL.NET>*Date*: Fri, 13 Feb 2004 14:10:49 -0800

I, of course, think the definition of cap. is fine. Like a bucket the

greater quantity it holds the greater the capacity, logical, n'est pas?

What is required is inverting R; call it conductance or some such name.

OTOH, one could invert C and call it incapacitance or pac? (cf. Mho)

bc

Folkerts, Timothy wrote:

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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