wrote:
But how did you know this little cylinder with a bump on the
end produced DC? And why can't DC circuits have net voltages
derived from superposition? Seems that in your model you need
extra information before you know what your voltmeter is telling you.

The extra information is that you are dealing with an RF transmission
line with reflections. The reflections are somewhat equivalent to
a second source. And in a two-source DC circuit, you can indeed have
net voltages derived from superposition of the two source voltages.
Put them in series adding and you get a voltage maximum. Put them in
series subtracting and you get a voltage minimum.

What about that power plug on the wall? Too difficult?

Too many sources, too many feedlines, too many loads. And the
wavelength is really too long to illustrate RF transmission lines.
I get a wavelength just over 3000 miles, which would stretch out
straight from Texas to Alaska.

When we measure a voltage using an ideal voltmeter, how do we know if
this voltage is composed of components ...

For an RF transmission line, use a directional wattmeter to ascertain
if reflected power exists. If your 50 ohm SWR meter is in a 50 ohm Z0
environment, it will indicate the presence or absence of reflected
power.

If you wish, the wall outlet provides an excellent opportunity for
explanation by example.

Nope, it doesn't. That wall outlet doesn't have one source, one feedline,
and one load. If you had one 60 Hz generator hooked up to 3100 miles of
lossless transmission line, you could certainly observe reflections over
that one wavelength of wire.
--
73, Cecil http://www.qsl.net/w5dxp



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