Jim Kelley wrote:
The arrow does not indicate "the direction AC is flowing" - which is
what you've been trying to imply.
Sorry Jim, I never tried to imply anything of the sort. The arrow,
which is just a convention, indicates the direction of instantaneous
current flow when cos(phase_angle) is positive which is during 1/2 of
the cycle. The instantaneous current flows in the opposite direction
1/2 cycle later when cos(phase_angle) is negative. You have argued loud
and long that current phase has nothing to do with current direction.
That's just simply false. In fact, the current phase and direction of
current flow in the wire are 100% correlated.
Moreover, it has nothing to do your
claim that more alternating current flows into one end of an inductor
than flows out of the other. As I have been saying all along, that
particular notion is invalid.
Tom's and Roy's own measurements proved that the measured current at
the bottom of the coil is greater than the measured current at the top
of the coil. Those currents are not standing still. They are flowing
in and out of the coil and have been proven not to be equal by actual
measurements.
Let's look at one example again. The current at the bottom of the coil
is 0.87 at -1.23 deg and the current at the top of the coil is 0.67 at
-1.57 deg. (Those angles deviate from zero degrees by a negligible
amount.) The cosines of those phase_angles are positive indicating that
we are on the '+' side of the axis (in phase with the feedpoint current)
so we draw the current arrow into the bottom of the coil and out the top
of the coil. Your objection to that commonly accepted convention is noted.
With the positive feedpoint current as our reference, we label the current
arrow pointing into the bottom of the coil as 0.87 amps and we label the
arrow pointing out of the top of the coil as 0.67 amps. So we have:
Source Current at Current at
Current Bottom of coil top of coil
1.0 amp 0.87 amp 0.67 amp
--- ---- coil ---
--------------------------------////////------------------------
At the time in the cycle when the instantaneous source current is
positive, the current into the bottom of the coil is positive and
greater than the current out of the top of the coil which is also
positive.
When the value I in the expression i = I*sin(w) for a standing wave
happens to be greater at one end of a transmission line than the
corresponding value of I at the other end of the transmission line, it
is NOT true, or correct to say that more current is flowing into one end
than is flowing out of the other. It's totally bogus electronics. I
wish you would be courageous enough to stand corrected on that point.
The net current is the phasor sum
of the forward current and reflected current. It can indeed vary from
one point in the transmission line to another and it does exactly that
in a line with reflections. I said long ago that the forward current
in a transmission line is relatively constant and the reflected current
is relatively constant. But their phasor sum, the net current, can vary
from zero to almost double the value of the forward current and anywhere
in between including positive and negative values. By convention, if it
is positive, it is flowing toward the load. If it is negative, it is
flowing toward the source. Non-zero standing-wave current reverses its
direction of flow every 1/2 cycle, i.e. it doesn't just stand still
contrary to its name. With a single inductive pickup, you cannot tell
a standing-wave current from a traveling-wave current. That fact speaks
volumes.
--
73, Cecil, W5DXP
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