View Single Post
  #918   Report Post  
Old April 3rd 06, 09:01 AM posted to rec.radio.amateur.antenna
K7ITM
 
Posts: n/a
Default Current through coils

Richard H wrote,

"Tom, K7ITM wrote:

"Given any volume, say a volume containing a Texas Bugcatcher coil and
the air inside and immediately around it, if you push more electrons in
than come out_for_ANY_arbitrarily_short_time_period_, you have changed
the net charge in that volume;---."

No. ..."

OK, I'm going to repeat it once mo

If you shove more electrons into ANY volume than you remove, you have
changed the charge within that volume. I do NOT care WHAT is in that
volume. Current is the rate that charge is flowing past a point on a
conductor. If the only way I have of getting charge into and out of a
particular volume is through two wires, then the difference in current
at every instant in time represents the time rate of change of charge
within that volume. That is true INDEPENDENT of whether it is in an
antenna, and it is INDEPENDENT of what's inside that volume.

In fact, energy around an antenna is stored in electric and magnetic
fields. These are inexorably linked to inductance along the conductors
composing the antenna, and capacitance from these conductors to
themselves and to any counterpoise or ground plane which may be part of
the antenna--anything where electric field lines terminate. The charge
per unit length along an antenna wire, be it resonant or not, be it a
"standing wave" or a "travelling wave" antenna, varies with time. If
it did not, then the current would necessarily be identical along the
whole wire all the time.

This all gets back to very basic definitions of charge, and current as
the rate of flow of charge. It's all consistent with Maxwell, Gauss,
Faraday, etc. and with waves both standing and travelling, and with
"impredances" and all the rest.

It's just amazing to me that some of you are fighting so hard against
the very thing which has a chance of unifying your "wave" model with
the realities of the electric and magnetic fields, and the associated
capacitance and inductance along the antenna--indeed, along the wire
itself, and not just along the coil.

Without capacitance, there can be NO difference in current anywhere
along the wire, because there is simply no place to put the charge
implied by differing currents at differing locations. With capacitance
and inductance, everything works just as it's supposed to--just as it
DOES--and a properly developed wave theory will analyze it just fine,
if that's your cup of tea.

Cheers,
Tom