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From: zben@umd5.UUCP
Newsgroups: net.analog
Subject: Re: Big Capacitors
Message-ID: <259@umd5.UUCP>
Date: Tue, 4-Dec-84 15:43:29 EST
Article-I.D.: umd5.259
Posted: Tue Dec  4 15:43:29 1984
Date-Received: Thu, 6-Dec-84 06:31:30 EST
References: <1812@sun.uucp> <1215@hou4b.UUCP> <6171@brl-tgr.ARPA> <10102@watmath.UUCP>
Reply-To: zben@umd5Cranston.UUCP (Ben Cranston)
Organization: U of Md, CSC, College Park, Md
Lines: 31

Sorry, but I have seen about enough pseudo-scientific garbage on this subject
to breakover and add my own two cents worth of pseudo-scientific garbage:

> Try a battery!  Your car probably has an electrolytic capacitor
> consisting of a liquid electrolyte and lead plates...many Farads, I
> think.   

> Seeing as the vague definition of a capacitor is "something which can
> store an electric charge", a rechargeable battery seems like a wonderful
> huge capacitor.   

Begin flame:  Yes, thats just about vague enough to be meaningless.  A more
precise definition of a capacitor is that it stores energy IN THE ELECTRIC
FIELD BETWEEN THE PLATES, just as an inductor stores energy in the magnetic
field that cuts the windings.  Now, a battery stores the energy chemically,
not as an electric field, so a battery, strictly speaking, is not the same
animal as a capacitor at all.

You cannot make a resonant circuit with a battery (I don't think).  The
discharge rate is limited by the chemical reaction rate.  Thats one huge
differance between a capacitor and a battery.

By the way, my homebrew machine (TI9900) was made from a Technico Super
Starter kit, but I designed and built the power supply.  I have 1/6 of a
farad on the +5 supply!  (Yes, the lights dim and it goes "buzz" for a
few seconds when I turn it on.  But +5 is clean!).  The can is 160,000
mikes at 10 volts and cost about $4.00 at the local surplus store.  Buy
yourself 6 or 7 and you too can have a one farad capacitor!

Bailed out of EE for CS, but I can still design power supplies...
Ben Cranston