Re: definition of "electrostatic"

["Bob Sciamanda" <trebor@velocity.net>]

Hi Bill!
I see your purpose!  I would still restrict the word "static" to mean
independent of time, not just a snapshot of a time dependent phenomenon.
We can save the day by observing that the DC current situation is a
hybrid combination:

Once the turn-on transient period is over, a static (unchanging) charge
distribution has been built up (and will be maintained) on wire surfaces
(and anywhere there is a spatial change in conductivity).  This static
charge makes the electrostatic field which drives the current.  The
charge distribution and the fields are static; the charge carriers are
moving  -  some call the entire situation a quasi-static situation.

This is also consistent with the mathematical definition of an
electrostatic field, ie; a conservative field, whose curl is zero.  Once
the circuit has settled down, the current is driven by just such a zero
curl, electrostatic field (except inside the EMF device, where an energy
source must lift the carriers up the potential hill  - to fall down again
in the external circuit under the influence of the electrostatic field).

The point is that electrostatic fields and static charge distributions
ARE the driving mechanism in the steady DC circuit, external to the EMF,
even using my (textbook) definition of "static".

-Bob

Bob Sciamanda
Physics, Edinboro Univ of PA (ret)
trebor@velocity.net
http://www.velocity.net/~trebor
-----Original Message-----
From: William Beaty <billb@eskimo.com>
To: phys-l@atlantis.uwf.edu <phys-l@atlantis.uwf.edu>
Date: Monday, October 05, 1998 9:30 PM
Subject: Re: definition of "electrostatic"


> On Mon, 5 Oct 1998, Bob Sciamanda wrote:
>
> > I guess I have to object, Bill.
> > The snapshot will not give you velocities and accelerations; it only
> > shows positions.
> > A snapshot of a charge system still on its way to equilibrium will
show
> > neither a dynamically nor an electrically "static" situation.  The
> > snapshot will not show that things are moving/accelerating.
>
> Very true.  Yet if we define "electrostatics" as "the study of electric
> potential, force, and charge distributions", then electrostatics does
> apply to dynamic phenomena.  Electrostatics then is not about "unmoving
> charge" so much as it is about "charge".
>
> I take this position as a result of encountering people who stoutly deny
> that "static electricity" has anything to do with simple circuits.
After
> all, the charge distributions on the surface of a closed circuit are
> participating in the electric current.  Therefor they are not "static",
> therefor "electrostatic charge", "electrostatic forces", and
> "electrostatic field" does not apply to circuits?  What?!
>
> I see this as a misconception which is created when people take the word
> "static" too literally.  And so I try to re-engineer the terminology by
> saying that "static" does not necessarily mean "still".  If I examine
one
> time-slice of an electrical phenomenon, then in part it is
> "electrostatic", and I can make predictions based on investigation of
> charges and fields.  Obviously there are other issues involved
> simultaneously.  But this does not mean that the "electrostatic"
concepts
> must all be discarded as soon as electric currents, induction,
radiation,
> etc. arise.  "Dynamics" does not erase "statics", it merely extends it.
>
>
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