Re: mag. force on wire?

[Bob Sciamanda <trebor@VELOCITY.NET>]

Thanks for the reference, Stanley.
If I read correctly this text is appealing to the charge separation cause
by the Hall effect, and asserting that the electrostatic field of this
charge separation acts on the lattice ions to move the wire!

I have a real problem - this force is one of a PAIR of forces INTERNAL TO
THE WIRE.  the net force on the wire due to the interaction of the
Hall-separated charges with the lattice ions is zero.

This is my quick reaction.  Will re-think and await comments of others.
I have never read diligently through this book, but have in general
applauded its approach.

Bob

Bob Sciamanda (W3NLV)
Physics, Edinboro Univ of PA (em)
trebor@velocity.net
http://www.velocity.net/~trebor

----- Original Message -----
From: Stan Greenspoon <sgreensp@CAPCOLLEGE.BC.CA>
To: <PHYS-L@lists.nau.edu>
Sent: Wednesday, November 03, 1999 12:51 PM
Subject: Re: mag. force on wire?


> For a good account of the charge separation explanation of magnetic
force on
> a current-carrying wire, see the relatively recent book  "Electric and
> Magnetic Interactions"  by Chabay and Sherwood. As a magnetic field
cannot
> do any work on a moving charge, the explanation for the work done by
> magnetic force (e.g. electric motors) is through the work done by the
> induced electric field due to charge separation on the lattice ions.
>
>
> Stan
>
> Stanley Greenspoon       Tel.:  (604) 986-1911 Ext. 2439
> Physics Department        Fax:  (604) 983-7520
> Capilano College
> 2055 Purcell Way
> North Vancouver, B.C.
> Canada
> V7J 3H5
>
>
> > Leon wondered:
> > > Just how is it that the force on moving charges
> > > "contained" in a wire is transferred to the wire
> > > itself? I've problems with the two explanations that
> > > seem pretty standard. That is, by collisions (with
> > > what, exactly, and what happens at the boundary?); and
> > > by electrostatic separation of charges (what happens
> > > if both positive and negative charges are equally
> > > responsible for charge flow?)
> >
> > I am not familiar with the "electrostatic separation" explanation; but
the
> > "collisions with the ion lattice" idea is a useful model.
> >
> > F=QVxB will produce the same direction of force for a given current
> > direction, however that current is divided among positive vs negative
> > carriers (both Q and V change sign)  That's why the force on a
conductor
> > can be evaluated in terms only of the current  (dF = I dLxB, where dL
is a
> > vector in the direction of the current) - with no regard to the
sign(s) of
> > the carriers.
> >
> > At the air/conductor boundary, any carriers forced off the surface
will be
> > called back and will call the conductor body toward them (by N3)
because
> > of  their "image charge" in the conductor.
> >
> > Hope this may be helpful - don't hesitate to prod further.
> >
> > Bob
> >
> > Bob Sciamanda (W3NLV)
> > Physics, Edinboro Univ of PA (em)
> > trebor@velocity.net
> > http://www.velocity.net/~trebor