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From: leonard@bucket.UUCP (Leonard Erickson)
Newsgroups: sci.electronics,sci.physics
Subject: Re: HV Cap Fun!
Keywords: capacitor,energy,paradox
Message-ID: <1441@bucket.UUCP>
Date: 4 Jun 89 22:00:07 GMT
References: <4924@m2c.M2C.ORG> <3806@mit-amt> <20772@quacky.mips.COM>
Reply-To: leonard@bucket.UUCP (Leonard Erickson)
Organization: Rick's Home Grown Unix; Portland, OR
Lines: 23

In article <20772@quacky.mips.COM> vaso@mips.COM (Vaso Bovan) writes:
<A Paradox of Capacitor Energy Storage
<
<I've heard several competing answers to this paradox. None is entirely
<satisfactory:
<
<Consider an ideal 2uF (for computational ease) capacitor charged by a 10 volt 
<source. Eventually, the energy stored is (1/2)*CV^2=100 joules.
<
<Consider the capacitor to be isolated from the voltage source, and then
<directly shorted across an identical (ideal) capacitor. Eventually, the
<voltage across each capacitor will be 5V. Now, there are two equally
<charged capacitors, each storing (1/2)*CV^2= 25 joules, for a total of
<of 50 joules.  What happened to the other 50 joules ?

I remember seeing this in an old physics text. The answer is that it radiates
the energy as EM radiation. After all, the energy is going to surge back and
forth for a while in any *real* system.
-- 
Leonard Erickson		...!tektronix!reed!percival!bucket!leonard
CIS: [70465,203]
"I'm all in favor of keeping dangerous weapons out of the hands of fools.
Let's start with typewriters." -- Solomon Short