Richard Clark wrote in message . ..
On 26 Mar 2004 17:47:01 -0800, (ieee std) wrote:

Folks:

I have one question. We know normal conductor current form a close
loop,
is this also true for displacement current ?

Yes, current does what current is.

In the following diagram, assume a an b are two long conductor wires,
...
Does this depend on the shape of abcd ?

Shape has little to do with it except when it comes to becoming a
significant source of linkage or leakage (going around the apparent
"open" circuit).

If displacement current must form a close loop, I think I_c = - I_d
must true, but is this the case ?

Hi OM,

This falls into the genre of the misapplication of DC/low frequency AC
circuit analysis to systems that are significant in size with relation
to wavelength. If you keep the physical dimension very much smaller
than the electrical dimension, then it will solve just like you
expect.

On the other hand, if the physical dimension is a significant portion
of an electrical wavelength, you will encounter paradoxes if you do
not use more elaborate math. Now, as to the scale of the paradox,
that all depends upon your tolerance to error.

73's
Richard Clark, KB7QHC


Thanks for your reply.

Do you mean that for low frequency AC circuit analysis, we can assume that
I_c = - I_d with some approximation ?