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From: kludge@grissom.larc.nasa.gov ( Scott Dorsey)
Newsgroups: sci.electronics
Subject: Re: polarity
Message-ID: <1991Apr29.132059.9403@news.larc.nasa.gov>
Date: 29 Apr 91 13:20:59 GMT
References: <11864@jarthur.Claremont.EDU> <1991Apr23.152315.22825@news.larc.nasa.gov> <1991Apr24.111307.2296@dcs.simpact.com> <2226@gold.gvg.tek.com>
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Reply-To: kludge@grissom.larc.nasa.gov ( Scott Dorsey)
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In article <2226@gold.gvg.tek.com> grege@gold.gvg.tek.com (Greg Ebert) writes:
>In article <1991Apr24.111307.2296@dcs.simpact.com> jeh@dcs.simpact.com writes:
>>you lost me here.  The hot side goes from +84 V to -84 V and back, referenced
>>to neutral, for a peak-to-peak swing of 168.  There is no "DC component"
>>anywhere.
>Almost. 120V RMS sinusoids are actually 340 v p-p, or 170 v peak. You are
>absolutely correct about there NOT being a DC component. If there *was*
>a DC component in your AC service, it would quickly saturate every
>inductive load. Hmmmm, sounds like a nasty prank ;-) .

Hmm... The point that I was making was that the signal was offset.  The zero
voltage point was at the bottom of the wave instead of the center.  I think that
imagining this as being a DC offset is a good way to look at it.  When you talk
about DC, you should ALWAYS talk about what ground level you are referring to,
because DC voltage levels are not useful without a reference.  If I consider
my reference ground to be the +5V terminal of a power supply, then your building
ground is probably floating at -5V.  (Okay, not a good analogy at all, granted).
--scott