Return-Path: Received: (qmail 31935 invoked from network); 8 Nov 2002 15:01:01 -0000 Received: from marstons.services.quay.plus.net (212.159.14.223) by mailstore with SMTP; 8 Nov 2002 15:01:01 -0000 Received: (qmail 14985 invoked by uid 10001); 8 Nov 2002 15:00:31 -0000 X-MSMail-Priority: High Received: from post.thorcom.com (193.82.116.70) by marstons.services.quay.plus.net with SMTP; 8 Nov 2002 15:00:31 -0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1106 Received: from majordom by post.thorcom.com with local (Exim 4.10) id 18AAaz-0004Pt-00 for rsgb_lf_group-outgoing@blacksheep.org; Fri, 08 Nov 2002 14:58:53 +0000 Received: from [212.1.130.1] (helo=smtp-1.visp.telinco.net) by post.thorcom.com with esmtp (Exim 4.10) id 18AAaz-0004Pk-00 for rsgb_lf_group@blacksheep.org; Fri, 08 Nov 2002 14:58:53 +0000 Received: from [212.1.141.198] (helo=standalone) by smtp-1.visp.telinco.net with smtp (Exim 3.32 #1) id 18AAUZ-0004bd-00 for rsgb_lf_group@blacksheep.org; Fri, 08 Nov 2002 14:52:15 +0000 Received: by localhost with Microsoft MAPI; Fri, 8 Nov 2002 14:57:31 -0000 Message-ID: <01C28737.29992A90.g4jnt@thersgb.net> From: "Andy talbot" To: rsgb_lf_group@blacksheep.org Date: Fri, 8 Nov 2002 14:57:28 -0000 Importance: high X-Priority: 1 X-Mailer: Microsoft Internet E-mail/MAPI - 8.0.0.4211 MIME-Version: 1.0 Subject: RE: LF: To Ponder over the weekend Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Status: No, hits=1.3 required=5.0tests=DEAR_SOMEBODY,SPAM_PHRASE_00_01,X_PRIORITY_HIGHversion=2.42 X-Spam-Level: * Sender: Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group Can tell you come from a university background Jim, do you ask that of applicants for courses at herts.ac? I was asked exactly the same question when applying for Southampton Uni. in 1976. Andy G4JNT -----Original Message----- From: James Moritz [SMTP:j.r.moritz@herts.ac.uk] Sent: 2002/11/08 11:52 To: rsgb_lf_group@blacksheep.org Subject: Re: LF: To Ponder over the weekend Dear Andy, LF group, At 09:38 08/11/2002 +0000, you wrote: >This simple puzzle caused more discussion in my office this morning than it >had any right to.... Here is another conundrum along similar lines - you have two identical, loss-free 1uF capacitors, one is charged to 10V, the other is discharged. You then connect the two in parallel so the total C is now 2uF - charge will flow from the charged capacitor into the discharged capacitor. Assuming charge Q is conserved, and that Q=CV, the voltage must now be 5V. But the stored energy in a capacitor =1/2CV^2, so with the single charged capacitor, the stored energy is 1/2 x 1u x 100 = 50uJ, while with both capacitors in parallel it is only 1/2 x 2u x 25 = 25uJ. So where has the other 25uJ gone? Cheers, Jim Moritz 73 de M0BMU