Article View: sci.electronics
Article #3254Re: A violation of the law of conservation of energy
From: Phil Ngai
Date: Fri, 29 Sep 1989 02:11
Date: Fri, 29 Sep 1989 02:11
18 lines
1378 bytes
1378 bytes
In article <318@massey.ac.nz> ARaman@massey.ac.nz (A.V. Raman) writes:
|By definition then, the energy transferred from V to C is
|charge * pressure = 1V * 1C = 1 joule
|But what is the energy stored in the capacitor?
|It is half C*square(V) = half * 1 * square(1) = half joule.
|Where has the remaining half joule gone?
|Beats me!
Congratulations, you've come up with an example which shows that the
circuit model of reality has idealizations which can lead to incorrect
answers. Any model of reality will have corners where they are not
useful. Part of your job as an engineer is to know when you are
getting close to one of those corners and what to do about it. In
this case, you have to go to a lower level and use an E&M model.
--
Phil Ngai, phil@diablo.amd.com {uunet,decwrl,ucbvax}!amdcad!phil
"Should the US send assault rifles to Colombia? How about small arms?"
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Path: arc1-ca.pugleaf.net!utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!ames!amdahl!amdcad!diablo!phil From: phil@diablo.amd.com (Phil Ngai) Newsgroups: sci.electronics,sci.physics Subject: Re: A violation of the law of conservation of energy Keywords: paradox Message-ID: <27549@amdcad.AMD.COM> Date: 29 Sep 89 02:11:58 GMT References: <318@massey.ac.nz> Sender: news@amdcad.AMD.COM Reply-To: phil@diablo.AMD.COM (Phil Ngai) Organization: Advanced Micro Devices, Inc. Sunnyvale CA Lines: 18