Re: Displacement Current Demonstration


Bill Miller wrote:
Hello Benj...

If Displacement Current is not the *cause* of a magnetic field, thus
satisfying the well known Dell cross H = J + dD/dt, then where the *H* does
the H come from?

It appears that it comes from the motion of charges as they are drawn toward
the surface/"pushed" away from the surface by the E field. I have put
together a fairly short description of what happens in a capacitor and it is
shown below: (I think... I've not tried to append rich text before.)

Forgive me that I haven't yet decoded your .gifs and followed your
arguments, but I still want to comment before I do that.

Yes, the question where indeed does the H come from. And it's worse
than that. If you look for example in a textbook like Plonsey and
Colin you'll find the usual statements that that if you have a "black
box" with a capacitor in it and you measure the magnetic field about
it, you can't tell what kind of capacitor is in there even though
Ampere's law fails if you compute it through the gap of the capacitor.
The displacement current is supposed to make the whole thing work.

So the question in my mind is indeed where does the H come from and
furthermore, if it comes from charge motion on the capacitor plates,
shouldn't it then create a magnetic field outside the "black box"
which is dependent upon the GEOMETRY of the given capacitor rather
that the implied "can't tell what's in the box" scenario?

These were the musing that got me wondering if indeed anyone had
actually tried any of these displacement current "black box"
experiments and tried to see if a field was indeed generated
independent of the capacitor geometry? And especially if an H field
can be generated in free empty space from a changing E field which is
the theory behind electromagnetic radiation. What kind of mechanism
can we imagine that would do that?

Benj

.

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