Cecil Moore wrote:
John Popelish wrote:

Since, in both standing waves and traveling waves, current at a point,
changes magnitude and sign in exactly the same way (at a point, they
are indistinguishable), they can both be described with phasor notation.


Limiting oneself to a point measurement is handicapping onself. When
the equation for standing wave current is compared to the equation
for traveling wave current, the real differences are obvious.

I was just making sure we were using the same definitions for things
like current and phasors. You are jumping ahead. :-)

For standing waves, the phasor of a neighboring point has the same
phase shift, ...


Exactly! Therefore, it cannot be used to measure the phase shift
through a coil or even through a wire.

I agree, unless you use phase measurement to hunt for the location of
the current nodes that have moved as a result of adding the coil.
Finding a phase reversal at opposite ends of the coil, for instance,
implies that an odd number of nodes reside in the coil.

But at any point along both standing waves and traveling waves, there
certainly is a phasor that represents the current at that point.

For the standing wave current it is a phasor that doesn't rotate
all up and down the wire.

A phasor rotates at the reference frequency, and with a phase angle
that represents the angular difference between the value in question
and the reference cycle. Pick a point on the conductor, and if it
carries either a standing or traveling wave (or any combination of
traveling waves at the reference frequency), the current at that point
is describable as a phasor (having a specific magnitude, and a
specific phase with respect to the reference cycle).

You have to admit, that's a weird phasor.
It's more akin to DC than anything else.

This is your mental block. A phasor describes the activity at a
point, not whether that activity is a result of an energy wave moving
past in one direction, the other, or some combination of those.

You need to get past this misconception that standing waves are not
current and are not describable by phasors.


Standing waves current is the superposition of two essentially equal
currents traveling in opposite directions.

No. Currents do not travel. Current is the movement of charge past a
point. Cyclic current is a sloshing back and forth of charge at some
frequency. If you want to picture that process with respect to time,
you can refer to it as a cycle or wave, but it is a wave on a scope
trace or time graph, not a physical wave of something moving along a
wire. The physical wave is charge slushing back and forth along the wire.

Both traveling energy waves and combinations of them (standing waves,
for example) involve energy traveling in various directions, but the
current does not travel. It occurs at a point, as charge moves back
and forth past that point. When you can separate the concept of
current from the concept of energy waves, you might see this snap into
focus.

I am not trying to be the guru, here. My earlier posts confused these
same concepts, when I mentioned current waves traveling in various
directions. I was mistaken, and have seen my error, and am trying to
get you to see it, also. I should have been speaking of charge waves
that produce current. Correct thinking requires correct speaking.
You cannot be sloppy with words and have (let alone express) clear
thoughts. This thread has done a lot to help me clear up both my
words and thoughts, and I thank you for that. I am not absolutely
sure that I have eliminated all mistakes from this way of talking
about the process under discussion, so I may have to make some more
corrections. That is the reason I am watching this thread.

If it was equal DC currents traveling in opposite directions,
what would the net current be?

Their algebraic sum, same as for non equal currents. Same for any
combination of currents that result from charge being shoved back and
forth by passing energy waves. Instantaneously the current is the
algebraic sum of all components passing through that point. If the
components are AC at the same frequency, the sum will be some
resultant instantaneous current that varies with that same frequency.

I think I agree with just about every conclusion you are making about
treating coils as slow wave transmission lines. The nits I am picking
is in the language you are using to describe these effects to justify
those conclusions. I think terminology is at the root of most of the
disagreements in this thread.