Will displacement current form a close loop ?
 

Folks:

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

In the following diagram, assume a an b are two long conductor wires,
form a close loop and source AC current flows in them, c and d are
another two long conductor wires, form a close loop too. There is no
source current in this loop. We want to investigate the induced
displacement due to source current in ab loop.

a b
+ -


+ -
c d


If we denote displacement current
from a to c as I_ac
from b to c as I_bc
from a to d as I_ad
from b to d as I_bd

Will I_ab = - I_bc ? (I do not think so, am I right ? )
Does this depend on the shape of abcd ?

Let I_c = I_ac + I_bc, total displacement current to c,
Let I_d = I_ad + I_bd, total displacement current to d,

will I_c = - I_d ?
Does this depend on the shape of abcd ?

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


Thanks.

Bow && Bow && Bow

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

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 ?

Bow et al wrote:
"We know normal conductor current form a closed loop, is this also true
for displacement current?"

AC circuits can be completed by capacitance. Countless coupling
capacitors demonstrate a-c flow on and through conducting parts of a
circuit. The same current flows via displacement through the dielectric
which inhibits charge conduction.

AC current is the same through a series path but moving charges that
produce electric force may go only back and forth in very short paths.

Conduction causes displacement and vice versa.

Best regards, Richard Harrison, KB5WZI