"Jim Kelley" bravely wrote to "All" (28 Nov 05 11:52:53)
--- on the heady topic of " Antenna reception theory"

JK From: Jim Kelley
JK Xref: core-easynews rec.radio.amateur.antenna:220506

JK Reg Edwards wrote:

It is impossible for an E-field to exist without an H-field.

JK Must have been before electrostatics was invented. :-)


Yes, but you are changing the topic into static fields. We were
discussing changing electric fields, not statics but dynamics!

A*s*i*m*o*v

.... "Hey, I'm just this guy, see?" --Zaphod Beeblebrox

Asimov wrote:
Yes, but you are changing the topic into static fields. We were
discussing changing electric fields, not statics but dynamics!

When is someone going to come up with a context-free language?
--
73, Cecil http://www.qsl.net/w5dxp

Asimov wrote:

"Jim Kelley" bravely wrote to "All" (28 Nov 05 11:52:53)
--- on the heady topic of " Antenna reception theory"

JK From: Jim Kelley
JK Xref: core-easynews rec.radio.amateur.antenna:220506

JK Reg Edwards wrote:

It is impossible for an E-field to exist without an H-field.

JK Must have been before electrostatics was invented. :-)


Yes, but you are changing the topic into static fields. We were
discussing changing electric fields, not statics but dynamics!

But do you agree that it's not impossible for an E field to exist
without an H field?

ac6xg

Jim Kelley wrote:
But do you agree that it's not impossible for an E field to exist
without an H field?

Depends upon the context. I suspect he was talking within the
context of RF EM waves? Is it possible for an RF E-field to
exist without an RF H-field?
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:

Jim Kelley wrote:

But do you agree that it's not impossible for an E field to exist
without an H field?


Depends upon the context. I suspect he was talking within the
context of RF EM waves?

That's certainly a context where an E field is always accompanied by an
H field. But the statement as it was written is nevertheless untrue.
That was my only point.

Is it possible for an RF E-field to
exist without an RF H-field?

Seems to beg an obvious answer. But the question brings up a point that
people seem to be missing here. An E field is an E field - there are not
different 'kinds' of E fields. The field itself is the same, whether it
varies in time or not. A non-zero dE/dt allows for some of the more
interesting properties to have non-zero solutions, but the fields
themselves are not unique. I hope that concept isn't too controversial
for this group. If it is, I will strive to keep such ideas to myself in
the future.

ac6xg

Jim Kelley wrote:
The field itself is the same, whether it varies in time or not.

I wonder if that's true when taken out of context? :-)

I'm no physicist but wouldn't a static electric field
be made up of virtual photons while a dynamic electric
field would be made up of non-virtual photons?
--
73, Cecil http://www.qsl.net/w5dxp

Cecil Moore wrote:
Jim Kelley wrote:

The field itself is the same, whether it varies in time or not.


I wonder if that's true when taken out of context? :-)

I'm no physicist but wouldn't a static electric field
be made up of virtual photons while a dynamic electric
field would be made up of non-virtual photons?

Non-virtual photons, as opposed virtual non-photons I presume. I think
physicists know they're going to have to wait until they get to the
pearly gates before they can really learn what "electric fields are made
out of". ;-)

73, jk

"Jim Kelley" bravely wrote to "All" (29 Nov 05 10:26:08)
--- on the heady topic of " Antenna reception theory"

JK From: Jim Kelley
JK Xref: core-easynews rec.radio.amateur.antenna:220548

JK Asimov wrote:

"Jim Kelley" bravely wrote to "All" (28 Nov 05 11:52:53)
--- on the heady topic of " Antenna reception theory"

JK From: Jim Kelley
JK Xref: core-easynews rec.radio.amateur.antenna:220506

JK Reg Edwards wrote:

It is impossible for an E-field to exist without an H-field.

JK Must have been before electrostatics was invented. :-)


Yes, but you are changing the topic into static fields. We were
discussing changing electric fields, not statics but dynamics!

JK But do you agree that it's not impossible for an E field to exist
JK without an H field?


A static E field can exist alone but to detect it requires something
like a field-mill which basically converts it into a changing EM field
that can be readily detected. A simple field-mill is basically a
rapidly spinning antenna. Relativity at work.

A*s*i*m*o*v

.... The truth is WAY out there!

"Asimov" wrote:

A static E field can exist alone but to detect it requires something
like a field-mill which basically converts it into a changing EM field
that can be readily detected. A simple field-mill is basically a
rapidly spinning antenna. Relativity at work.

It's similar in some ways to a method for detecting magnetic fields used
prior to the advent of Hall effect devices. Not sure how it relates to
relativity.

Perhaps it's true that an electric field is simpler create than to
detect by direct means. But it isn't really any more difficult than,
for example, measuring power by direct means. I think Ben Franklin
measured the E field in a Leyden Jar by calibrating the leaf
displacement caused by the Coulomb force resulting from the electric
field between the two similarly charged surfaces.

jk

"Jim Kelley" bravely wrote to "All" (29 Nov 05 14:46:41)
--- on the heady topic of " Antenna reception theory"

JK From: Jim Kelley
JK Xref: core-easynews rec.radio.amateur.antenna:220573

JK "Asimov" wrote:

A static E field can exist alone but to detect it requires something
like a field-mill

JK It's similar in some ways to a method for detecting magnetic fields
JK used prior to the advent of Hall effect devices. Not sure how it
JK relates to relativity.

I think a saturable core can be used to measure a static magnetic
field. Early computer magnetic core memories worked like this.

Relativity transforms static fields into dynamic fields by adding a
velocity component to the measurement.


JK Perhaps it's true that an electric field is simpler create than to
JK detect by direct means. But it isn't really any more difficult than,
JK for example, measuring power by direct means. I think Ben Franklin
JK measured the E field in a Leyden Jar by calibrating the leaf
JK displacement caused by the Coulomb force resulting from the electric
JK field between the two similarly charged surfaces.

That Leyden Jar experiment was measuring charges not the E field
itself. An E field doesn't require the exchange of charges.
I wonder if it is possible to directly measure an E field by the
effect of the virtual quanta in its close vicinity?

A*s*i*m*o*v

.... Quoting one is plagiarism. Quoting many is research.