"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.

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

E =IR

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. 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".

j