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# [Phys-L] Re: Fields etc

• From: Jack Uretsky <jlu@HEP.ANL.GOV>
• Date: Tue, 29 Mar 2005 19:20:41 -0600

Faraday would do. There have been some advances since then, and I'd have
to do some research. Since c is a defined quantity, the measurements
needed are the fine structure constant and Planck's constant. I'll let
someone else pursue this question.

On Mon, 28 Mar 2005, Bernard Cleyet wrote:

How the standard is determined is beyond the scope of this posting.

-----

That is exactly what I want.

bc

p.s. You don't mean a chemical method, do you? (Faraday)

Jack Uretsky wrote:

Is not to worry. I have a standard charge that I keep at NIST, in
Boulder. I take a sample, that I
label "test" to Boulder, and I measure the force on "test" at a
distance of 1 m. This gives me the charge on "test". Now I carry
"test" around in some space and go through the procedure previously
described.

All charges are of course measured with respect to the standard. How
the standard is determined is beyond the scope of this posting.

Bernard Cleyet wrote:

Jack, I don't know if I'm walking into a mine field here, but I think
we got circularity here.

I think the charge is defined (measured) by the force, not the other way
around.

bc, worried.

Jack Uretsky wrote:

Go back to basics, in this case the definition of "field". Charged
objects, in a certain region, experience forces that are proportional to
the charges, and for each object there is a unique force vector at each
point of the region. Divide the force vector by the associated charge on
the object. The resulting set of vectors is called the "vector field in
the region". Is it real? Depends upon your definition of reality. The
force vectors were measurable; does that fact make them "real"? This is,
an example that is appropriate to an electrostatic of gravitational field.

A vector field is, simply stated, a process that assigns a unique vector
to each point of a space - where I use "space" in a generalized sense that
includes ordinary 3-d space as a special case.

Regards,
Jack

--
"Trust me. I have a lot of experience at this."
General Custer's unremembered message to his men,
just before leading them into the Little Big Horn Valley

--
"Trust me. I have a lot of experience at this."
General Custer's unremembered message to his men,
just before leading them into the Little Big Horn Valley
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