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Re: funny capacitor



Furthermore, the fact that Cij is a partial derivative tells you how to
calculate it - it does does *not* mean that in the *physical* world only one
of the independent variables can change at a time. You are again
surepticiously imposing a constraint on the *independent Vj's.

Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
www.velocity.net/~trebor
----- Original Message -----
From: "Bob Sciamanda" <trebor@VELOCITY.NET>
To: <PHYS-L@lists.nau.edu>
Sent: Tuesday, March 06, 2001 7:17 PM
Subject: Re: funny capacitor


The "object at infinity" is not a part of the one-conductor system under
consideration.

Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
www.velocity.net/~trebor
----- Original Message -----
From: "John S. Denker" <jsd@MONMOUTH.COM>
To: <PHYS-L@lists.nau.edu>
Sent: Tuesday, March 06, 2001 6:11 PM
Subject: Re: funny capacitor


At 05:50 PM 3/6/01 -0500, Bob Sciamanda wrote:

Consider our old friend the single, isolated conductor and its
description:
Q = C V, where C = C11, the only Cij of this one-conductor system.
Let's make it a sphere of radius a. Then if V is referred to infinity
C=4*PI*epsilon*a.
OTOH if V is referred to a space-point located a distance 2a from the
sphere's center, then C=8*PI*epsilon*a.

Nice try, but alas that violates the defining relationship
Cij := delta Qi / delta Vj (all Vk const except
Vj)

because the voltage of the "object" at infinity is changing when the V
of
the sphere changes.