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Old March 26th 06, 03:05 PM posted to rec.radio.amateur.antenna
John Popelish
 
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Default Current through coils

Cecil Moore wrote:
John Popelish wrote:
Cecil Moore wrote:
John Popelish wrote:


If the sensor sits at a single point and sees an AC current,
you have no way, from this one measurement, if this current
is the result of a standing wave (two oppositely traveling
equal waves adding), or a single traveling wave,
or any combination of traveling waves of different amplitudes.
You know only the net current at that point.


But if one it smart enough to slide the sensor up and down
the wire and note the phase is fixed and unchanging,
one knows he is dealing with a standing wave.


Another point, entirely.
My point is that current has a point definition,
and standing wave current is certainly indistinguishable
from traveling wave current, at a point. Current is current.

Patterns of current over length is another subject. But you keep
saying that there is something different about current in a standing
wave. There isn't.


Do you really think that func(kx)*func(wt) is the same thing as
func(kx +/- wt)? If so, time to dust off the old math books.


( I restored some context)

func(kx)*func(wt) describes the instantaneous current if you pick a
point along dimension, x, and a moment in time, t. It is a map of the
pattern of current over these two dimensions.

func(kx +/- wt) describes a different pattern of the instantaneous
current if you pick a point along dimension, x, and a moment in time, t.

If you put a tiny current transformer around some point of the
conductors in question, (pick an x) and watch the pattern of current
through time (without comparing the phase to any reference) you will
see a sinusoidal current variation for both the standing and traveling
wave cases. The amplitude will vary in a different way, over x, for
the traveling and standing wave cases. If you include comparing the
phase of sinusoidal current cycle you see, to a reference phase, that
will also vary in a different way over x, for the traveling and
standing wave cases.

But regardless, at a point (any particular x) the pattern of current
variation as time passes, will be a sinusoid, in either case. There
is no difference in kind of current you would measure.

The pattern of how this sinusoidal current varies in both phase and
magnitude is very different in the two cases (standing and traveling
waves), but you need both a phase reference and multiple locations to
see the differences.

The the definition of the word "current", in simplest form, is, the
rate of charge movement past a point at some moment in time.

An extension of this instantaneous and point definition might include
a sinusoidal cyclic variation through time, by adding a frequency,
phase and amplitude, to specify a common pattern of current over time,
but still at a point.

Adding in an additional function of position allows the extension of
this definition of current over time to also include spacial variation
of the time dependent pattern.

But if you say the words "the current is different", and don't include
a lot of additional verbiage to indicate that you are talking about
the two dimensional pattern of the variation of current over time and
location, some people are going to misunderstand you and argue based
on picturing another definition of what might be legitimately meant by
the word, "current". I made it clear what definition I was using for
the word "current" (the instantaneous point definition) and you are
arguing with me, while using some different definition.

I realize that I am being pedantic, here, and stating the painfully
obvious. But if your goal is to have other minds synchronize with the
abstract thoughts rippling through your mind, you have to be pedantic.

If you are just using this topic to argue, because you enjoy argument,

then never mind.