"operator jay" wrote:
"Floyd L. Davidson" wrote in message
...
"operator jay" wrote:
"Floyd L. Davidson" wrote in message
...

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:

Reference Direction
Point of flow
========= =====================================

Peak Pos All Negative

DC level Equal cycles of Positive and Negative

Peak Neg All Positive



I think "zero" is a good reference for current flow, and that the actual

Sure... now, can you define "zero"?


Put an ammeter there and it says zero. That's zero. Electrons bouncing
around in the conductor have an average net displacement, over time, of 0.

Is this an AC ammeter, or a DC ammeter? (And isn't that just a voltmeter
anyway, in most actual cases????) Hmmm...

(absolute) direction can be measured. Voltages have the reference
issues.

E =IR

You can't escape the fact that voltage and current are joined at
the hip, they are for all practical purposes different expressions
of the same thing. Whatever affects one *has* to have affected the
other.

Since our resistance is fixed, it's the exact same issue, though
perhaps easier to understand, with voltage. (I gave some
consideration as to whether to post that with voltage or current
references, and since "AC" and "DC" use the term "current",
decided to go with current to avoid the easier path to the same
statement you are making.)


Current is a different issue from voltage because voltage is a relative
quantity.

No more or less than current. They are joined at a hip called
Ohm's Law.

It is a type of measurement of a change in field between two
locations. Current is a rate of flow of charge at a single location (well,
typically, through a single Gaussian surface), and is measurable at that
location, and does not have the ambiguity that voltage has. It does not
need a reference. If I say that my toaster is running at 120V and 8A, you
may ask "120V relative to what" and I'll answer "neutral". You would not
ask "8A relative to what".

8 Amps from where? To where? Through were?

Relative to where?

Since we can discuss current using only voltage as the variable
(resistance being a constant in this example), *anything* you
can say about voltage is directly related to current.

One of the overall things that you *have* to keep in mind is
that periodic reality checks are necessary. One of them is the
fact, repeated by many in this thread, that "DC sine wave" is a
contradiction of terms. If your definition makes it possible,
your definition *can't* be right.

My point still stands, that if the current is changing, it is by
definition AC, and current not changing is DC. Trying to look
at it as DC is all in one direction and anything else is AC,
doesn't work.

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