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Re: Displacement current- is it real (was 7.1Hz)



Original poster: "Chuck Hobson" <g0mdk@xxxxxxxxxxxxx>


----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx> To: <tesla@xxxxxxxxxx> Sent: Tuesday, July 19, 2005 4:37 PM Subject: Displacement current- is it real (was 7.1Hz)


Original poster: Steve Conner <steve@xxxxxxxxxxxx>

> So with your
> indulgence, I will make a
> few observations regarding criteria that must apply
> to displacement
> currents.

Stork, I guess I agree with every assertion you made
except #4.

> 4.  No magnetic fields are experimentally measurable
> in dispalcement
> currents in dielectrics.

But I don't really disagree with #4 either. I just
don't know whether it is true or not. When testing it,
I don't know how you would separate the (supposed)
field due to the displacement currents, from the
fields due to the conduction currents feeding the
plates of your test capacitor.

Maxwell himself seems to say that #4 is false, as one
of his equations is:

curl H=J+dD/dt

suggesting that displacement currents (dD/dt) create
loops of H-field just as if they were conduction
currents (J). Indeed this is the argument for how
radio waves propagate, with H-fields turning into
E-fields and back again as they fly along.

This suggests that the E and H fields are 90 degrees with respect to each other as they travel out in space. The cross product in this case would result in
the orthogonal vector = E sin(omega-t) - H cos(omega-t) Now if you work out the Energy in the E field you'd get Joules/m cube. The same for H field. The sum of these energies would be continuous (like the energy in a perfect oscillating LC circuit. The energy would be constant, while the E and H components vary at a sinusoidal rate.) So much for the poynting vector notion. What do you think?


I don't care what Paul Nicholson says, I'm off to wind
a big Rogowski coil and shoot some displacement
current through the hole in the middle :)))

Steve Conner

Sorry I'm late with my thoughts on this. I hope it doesn't disrupt this most interesting thread


Chuck Hobson