On Jan 5, 1:07*am, mike wrote:
* Keith Dysart wrote:

* On Jan 3, 12:55pm, Mike Monett wrote:

* [...]

* Your explanation *is *easily proven false. Let's *suppose *it was
* true.

* Suppose it *was *possible to introduce a pulse of *charge *onto a
* conductor.

* Since like *charges *repel *each * other, *what *keeps *the pulse
* together? In *other *words, * what *prevents *it *from destroying
* itself?

* Then, when *the *first *pulse meets *the *second, *what mechanism
* allows them to bounce off each other?

* Then, after *they *have bounced off *each *other, *what mechanism
* keeps them together?

* All good questions.

* For which you have no answers.

* But there's more bad news. Here's your original post of Dec 29:

* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~
* Subject: Standing-Wave Current vs Traveling-Wave Current
* Date: Sat, 29 Dec 2007 14:33:46 -0800 (PST)
* From: Keith Dysart
* Newsgroups: rec.radio.amateur.antenna

* Keith Dysart wrote:

* [...]

* Consider a 50 ohm transmission line that is 4 seconds long *with a
* pulse generator at one end and a 50 ohm resistor at the other.

* The pulse generator generates a single 1 second pulse of *50 volts
* into the line. Before and after the pulse its output voltage is 0.

* While generating the pulse, 1 amp (1 coulomb/s) is being *put into
* the line, so the generator is providing 50 watts to the line.

* After one second the pulse is completely in the line.

* The pulse is one second long, contains 1 coulomb of charge *and 50
* joules of energy. It is 50 volts with 1 amp: 50 watts.

* Let's examine the midpoint (2 second) on the line.

* At two *seconds *the *leading edge of *the *pulse *arrives *at the
* midpoint. The voltage rises to 50 volts and the current *becomes 1
* amp. One *second later, the voltage drops back to 0, *as *does the
* current. The *charge *and the energy *have *completely *passed the
* midpoint.

* When the *pulse *reaches *the *end *of *the *line, *50 *joules are
* dissipated in the terminating resistor.

* Notice a *key *point about this description. It *is *completely in
* terms of *charge. *There *is not a *single *mention *of *EM waves,
* travelling or otherwise.

* Now we expand the experiment by placing a pulse generator *at each
* end of *the *line and triggering them to each generate *a *50V one
* second pulse *at *the same time. So after one second *a *pulse has
* completely entered each end of the line and these pulse are racing
* towards each other at the speed of light (in the line). In another
* second these pulses will collide at the middle of the line.

* What will *happen? *Recall one of the *basics *about *charge: like
* charge repel. So it is no surprise that these two pulses of charge
* bounce off each and head back from where they came. At *the center
* of the *line, for one second the voltage is 100 V (50 V *from each
* pulse), while *the current is always zero. No *charge *crossed the
* mid-point. No *energy crossed the mid-point (how could *it *if the
* current is always zero (i.e. no charge moves) at the mid-point.

* [...]

* So do the travelling waves "reflect" off each other? Save the term
* "reflect" *for * those * cases * where * there * is * an impedance
* discontinuity and use "bounce" for those cases where no *energy is
* crossing a point and even Cecil may be happy. But bounce it does.

* Keith

* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~
* In order *for *the *pulses to bounce *off *each *other, *your theory
* requires that electrons move at nearly the speed of light.

It might best be called a hypothesis, but I don't think
it requires that electrons move at the speed of light,
rather charge move at the speed of light.

This would seem consistent with normal explanations where
charge starts to enter the line at some time T and starts
to exit the line at T + distance/speedOfLight later.

[snipped, an interesting computation of the speed of
electros]


* There's more *bad *news. If two collections of 1 *Coulomb *each were
* concentrated one *meter *apart, *the *force *between *them *could be
* calculated from *Coulomb's Law. In this example, the *force *is 1.01
* million tons:

* *http://hyperphysics.phy-astr.gsu.edu...ic/elefor.html

* This means the pulses could not even come close enough to bounce off
* each other. *This would certainly wreck any timing analysis *you try
* to do on the signals.

Another interesting analysis. It raises the question of how
a pulse containing one coulomb over a measurable length of
line actually maintains its shape and does not immediately
disperse.

This is a detail well beyond my knowledge, but I could
speculate that it is related to the inductance and
forces of the resulting magnetic field.

I'd further speculate that the force between the pulses
can not travel faster than the speed of light, and since
the pulse itself is travelling at the speed of light,
the two pulses reach each other at the same time that
force does.

* So your *theory *fails *simple * logic *tests, *it *requires invalid
* electron velocities, and it fails Coulomb's law.

* It is *clear the pulses cannot bounce off each other, *as *you claim
* above when you state "But bounce it does."

* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~
* But it appears that your underlying suggestion is that *charge and
* charge flow in the distributed capacitance and inductance *can not
* be used to analyze transmission lines.

* That is not what you proposed. Your post states:

Perhaps I was not clear in my post.

In any case, the question is fundamental...

Can charge and charge flow in the distributed capacitance and
inductance be used to analyze transmission lines?

* Notice a *key *point about this description. It *is *completely in
* terms of *charge. *There *is not a *single *mention *of *EM waves,
* travelling or otherwise.

* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~~
* And yet *I *commonly *see discussion *of *current *in transmission
* lines. Current is charge flow per unit time. Is this all invalid?

* Must we *abondon measurements of current? Voltage? *These *are all
* based on the assumption of charge being a useful concept.

* You are *just *trying *to fog the issue. You *cannot *use *charge by
* itself as you claim above.

No. I am just trying to make clear the consequences of choosing
"no" as the answer to the question I directly posed above.

...Keith