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Old December 10th 08, 05:54 AM posted to rec.radio.amateur.antenna
Art Unwin Art Unwin is offline
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First recorded activity by RadioBanter: Mar 2008
Posts: 1,339
Default skin depth (eddy current/Foucault currentO)

On Dec 9, 3:39*pm, (Richard Harrison) wrote:
Art wrote:

"So what exactly forces a time varying current to take an alternate
route of travel from the center of the conductor when the resistance is
so low compared to other routes that could be taken?"

Opposing ac current is total impedance, not just resistance.

I tthink you have to go back to the beginning of this thread as again
you are talking out of context.
My statement referes to the current path on a fractional waqve antenna
when it reaches the top.
My point was that the current then procedes to the INSIDE of the
radiator where the AC current cannot produce
an eddy current and thus the opposition to current flow in the centre
is just a copper loss i.e.resistance.
This statement was made in requesting a possible different current
path from the top of the radiator
that provided a lower resistive path. I.E I pointed out that the
impedance dropped linearly with respect to radiator length
and thus I wanted a mathematically demonstrated different path that
would counter my initial assertion.



The deepest fibers in a conductor are encircled by the largest number
magnetic flux linkages. These create a reactance which generates a
counter-emf opposing an imposed current. The deeper the depth inside a
conductor, the greater the opposition to the imposed current.


I think I have stated what skin depth is and what created it many
times so I won't respond
to the above paragraph




Look for "skin effect" in any edition of Terman and you will find
diagrams illustrating the various magnetic flux paths inside the
conductor which cause skin effect.


I believe that the Wilkedia URL and Ian's supplied scanned page
is adequate descriptions where the initial supplied current is the sum
of the two currents in the circuit one of
which is Maxwells determination of displacement current i.e.a current
that displaces while providing an accelleration to PARTICLES (charges)
from the surface of a radiator.
If you can give an specific answer in mathematical form to the initial
question asked it would be apreciated
Other than that there is no need for continuation of this thread.





Best regards, Richard Harrison, KB5WZI