Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!ucbvax!hplabs!hpfcso!hpfcdj!myers
From: myers@hpfcdj.HP.COM (Bob Myers)
Newsgroups: sci.electronics
Subject: Re: A violation of the law of conservation of energy
Message-ID: <17660022@hpfcdj.HP.COM>
Date: 27 Sep 89 18:47:55 GMT
References: <318@massey.ac.nz>
Organization: Hewlett Packard -- Fort Collins, CO
Lines: 35

-> This problem has puzzled me for 2 years
-> Can someone please help me out:
->                        ________________
->                       |                |
->                    V ---             ----- C
->                   ---------          -----
->                       |                |
->                        -----RRRRR------
-> 
>	The summary says it all.  I ain't gonna say another word. :-)


You're a cruel man, Larry! :-)

*I* will at least give a hint -

Consider that even if R is zero, the voltage V *cannot* appear across the
capacitor instantaneously; to do so would require the charge be transferred
INSTANTLY to the capacitor, which means an infinite current (for an infinitely
small - actually, zero - time!).  Such is not truly possible if there is
any physical distance at all between the source and capacitor (and if there
isn't, where does the "C" come from? :-)).  The usual means of modelling the
behavior of this circuit break down in this extreme case, and we must
fall back on what's actually happening.  Consult a good EM text for further
details - but only AFTER you've thought about it a little further.

(And yes, this is very similar to the old two-capacitor problem discussed
a few months ago; so if someone thinks that they're being clever by
posting that problem in a new guise, well, a pox upon thee and I wish to
Zeus I'd kept my flinkin' mouth shut.  Shoulda left Larry's response stand. :-))


Bob Myers            | "The difference between science and the fuzzy subjects
myers%hpfcla@hplabs. |   is that science requires reasoning, while those other
hp.com               |     subjects merely require scholarahip." - R. Heinlein