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Re: Definition of Capacitance

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)


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
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