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From: dbell@cup.portal.com (David J Bell)
Newsgroups: sci.electronics,sci.physics
Subject: Re: HV Cap Fun!
Message-ID: <19182@cup.portal.com>
Date: 6 Jun 89 19:45:21 GMT
References: <4924@m2c.M2C.ORG> <3806@mit-amt> <20772@quacky.mips.COM> <8739@fluke.COM> <8742@fluke.COM>
Organization: The Portal System (TM)
Lines: 30

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 ?

     [etc., etc....  much discussion omitted...]

Hmmm...    U = 1/2 C V^2   (V = volts)
          Ke = 1/2 M V^2   (V = velocity)

Lessee: Two billiard balls, equal mass, one traveling...

      etc...    

In other words, discharging one cap into the other through a *real* world
circuit is equivalent to elastic collision and dissipated energy.

Whataya know; duality everywhere!

Dave        dbell@cup.portal.com