On Fri, 24 Mar 2006 20:13:26 -0500, John Popelish
wrote:

He and others have given this as
proof that the current at the two ends of an inductor are inherently
different, regardless of its physical size.

I agree up till you add, "regardless of physical size". I have seen
him talk only about large air core space wound coils. I came to the
discussion late, but this is what I have seen.

Hi John,

One of the problems is the thread discussion is freely mixed with
practical observations and theoretical arguments - these can clash,
especially when mixed indiscriminately to prove one point.

First, several years ago, came the shocking observation that the
current into a coil is not the same as the current out of it.
Somewhere along the debate, this practical measurement was then
expressed to be in conflict with Kirchhoff's theories. However,
Kirchhoff's current law is for currents into and out of the same point
intersection, not component. The association with a point is found in
that the "lumped" inductance is a dimensionless load. The association
with Kirchhoff was strained to fit the load to then condemn the load
instead of simply rejecting that failed model and using the correct
one.

The problem came from incorrectly specifying the coil in EZNEC which
offers a coil generator (inductor) in the wires table as well as a
coil specification (inductance) in the loads table. This shocking
difference between model and observation would have been easily
resolved by simply using the coil generator (inductor) in place of the
lumped equivalent (inductance).

How do you know when you've made a mistake in application? You do two
designs and compare each to what nature provides. You discard the
model that does not conform to nature.

Want to know what the difference is between the two (the good and the
bad design) at the far receiver? ±.32dB Hence the name of my thread
"Current through coils - BFD."

....snip

But the ground is there, in the application under discussion. All
components act differently if you connect them to something else.
This coil is connected to ground by its capacitance.

Roy's point is that the proposed "theory," as Ian has also pointed
out, has to correctly answer all scenarios, not just one. We don't
have enough shelf space in libraries that prove the resistance of each
resistor constructed - one formula does quite well for 99.999% of
them, and a couple more formulas for those that don't (and those new
formulas will give the same answer for the first 99.999% as well).

When you add ground to the model, you
have to add the equivalent shunt C to the lumped model. The C isn't a
property of the inductor itself; it's the capacitance between the
inductor and ground.

That is a very strange statement to my mind. Stray capacitance is an
unavoidable effect that any real inductor in any real application will
have as a result of it having non zero size.

You are mixing an observational fact with a theoretical statement. The
lumped model contains ONLY inductance, to make it conform to nature,
as Roy is doing here, you have to add in all the nasty bits.

OR

Build a helix (inductor) in the wires table.

A thing made of wire
that takes up space has inductive character and capacitive character,
and transmission line character, and loss, all rolled into one.

These are all properties that reside in a helix (inductor) constructed
in the wires table. Some of these properties (like inductance) also
reside in the load table, but not the capacitance to earth. If it
matters, it is up to you to make the correct choice.

....snip

Well, the rest was more conflict between theory and practice that is
and has been resolvable for a long time. Even the conflict is
separable. For those who persist in making poor choices, they will
always have either a problem with a model, or the genesis of a new
theory, or rattle on beyond 500 posts - sometimes all three.

73's
Richard Clark, KB7QHC