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