John Fields wrote:
On Sun, 12 Jun 2005 17:15:06 -0700, Don Lancaster
wrote:

Sum a 1 volt peak sinewave with a 0.6 volt dc term and you have a
waveform whose polarity continuously changes but whose average value is
continuous.

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No, you have a waveform with a polarity which changes _periodically_,
making it an AC signal. Do the electrons traversing the circuit
change direction? Yes. Do the electrons in a DC circuit ever change
direction? No.

Ergo, because of the periodic polarity reversals what you're looking
at is AC.

And, according to what you've said in other posts, if that were a
0.6 volt peak sinewave with 1.0 volt dc, it wouldn't be.

But your definition of AC is faulty, because in fact they are the
same thing, and *both* of them contain an AC component and a DC
component, even if the general direction of electrons is always the
same.

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Looking at the Fourier terms makes this waveform perfectly clear.
Calling it "AC" or "DC" does not.

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Why go there? Your description was adequate to indicate that polarity
reversals occur, therefore making the signal voltage alternate between
two different polarities, therefore making the current alternate
between polarities as well. That's why it's called "Alternating
Current".

Except, polarity reversals are not significant to the definition
of AC.

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"AC" or "DC" are gross and meaningless oversimplifications.

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Uh-huh...

He's right.

--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)