Re: mag. force on wire?

[Stan Greenspoon <sgreensp@CAPCOLLEGE.BC.CA>]

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
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> 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