"Kevin Aylward" wrote in message
...
Floyd L. Davidson wrote:
Bob Penoyer wrote:
On Sat, 11 Jun 2005 10:36:54 -0400, "Tam/WB2TT"
wrote:

snip

Yes. DC by definition is zero frequency.

Um, no. DC is Direct Current, i.e., current that flows in one
direction. For example, the output from a rectifier is DC but it
certainly isn't "zero frequency."

Actually, DC from a rectifier *is* "zero frequency", to the
degree that it is DC. Of course until the AC is filtered out,
it has both AC and DC components.

The output of a rectifier contains both AC and DC. You put a filter
on it to get close to pure DC.

That is *precisely* correct. (It just doesn't tell enough of
the story to explain the confusion of this "flows in one
direction" definition of DC.)

A rectified AC waveform contains DC and AC components but if the
current isn't changing direction, it isn't alternating current. And,
if it isn't AC, it's DC.

The output of a rectifier until filtered *does* have both AC and
DC, which actually is another way of saying that yes it *does*
change directions.

What? you say!

The problem is that "direction" only has meaning when measured
in comparison some specific point of reference. If you have
three different reference points, one at the DC level, one at
the peak positive swing and one at the peak negative swing, you
have three very different views of "direction" for current flow:

Since we are quibbling her on terms, lets get this bit straight shall
we.

"Current flow" is wrong. Its simply "current" or "charge flow".
"Current" already contains the notion of "flow".

Atta boy, Kevin. Ratch



Kevin Aylward

http://www.anasoft.co.uk
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