Re: CHARGED CAPACITOR TERM

[William Beaty <billb@eskimo.com>]

On Sun, 15 Feb 1998, LUDWIK KOWALSKI wrote:

> I tend to agree with Bob that we have more potentially domaging 
> misconceptions than the one which can possibly result from taking the 
> phrase "charging a capacitor" in a perverted way. But the phrase 
> "energizing it" is probably better and I will start using it.

I agree somewhat.  This discussion did not start with my objections to
"charging" and "discharging."  I had first added this misconception to
Ludwik's list:

 36) 2-plate capacitors are charged with energy, not with electrical
     charge. A charged capacitor contains just as many + and - charged
     particles as a discharged capacitor.


I still insist that "capacitors store charge" is a misconception.  In
addition to this issue, I found that I grow uncomfortable when I tell
someone that I've "charged" or "discharged" a capacitor.  But this
terminology problem is not the central issue, and I see that I got going
on it while devoting less energy to the original issue, #36 above. 

The plates of a 2-plate capacitor, when considered individually, obviously
do store charge.  But the "capacitor" device used in electronic equipment
normally does not.  That is not its intended function.  If I surround a
capacitor with a spherical Gaussian surface, then during "charging" no
charge is delivered into that surface.  And during "discharge", no
charge exits through  that surface.

I do agree that a 2-plate capacitor can be made to store charge if a third
plate is provided.  If I twist the leads of a 10uF electrolytic capacitor
together and briefly touch them to the terminal of a VandeGraaff
generator, then my capacitor does store charge, with opposite charge being
stored on earth-ground. 


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