Re: [Phys-l] Magnetic force and work

["Bob Sciamanda" <trebor@winbeam.com>]

1) I think there is an error in your choice of directions, John.  With the 
magnetic field directed into the page, a positive charge moving in the 
direction of the RED F vector will experience a qVxB force to the LEFT, 
antiparallel to the BLUE F vector.
2) You say: "The wire exerts a force on the particles, and by the same token 
the particles exert a force on the wire.".
The current carrying particles are part of the wire.  Your statement 
describes a net (internal) force of ZERO on the wire system. The wire must 
be moved by an external force.

Bob Sciamanda
Physics, Edinboro Univ of PA (Em)
http://www.winbeam.com/~trebor/
trebor@velocity.net
----- Original Message ----- 
From: "John Denker" <jsd@av8n.com>
To: "Forum for Physics Educators" <phys-l@carnot.physics.buffalo.edu>
Sent: Sunday, March 26, 2006 3:30 PM
Subject: Re: [Phys-l] Magnetic force and work



Since people seem to be interested in this, I cobbled up a diagram
showing what happens to charged particles in a wire in a magnetic
field, along with a couple hundred words of explanation.
  http://www.av8n.com/physics/current-wire-field.htm


At one point it says:

> It is a fool’s errand to argue about whether the force on the wire is 
> “because” of the magnetic
> force on the particles, or “because” of the force of constraint. You need 
> both the magnetic force
>  and the force of constraint to explain the observed phenomena.


Also, I expanded, illustrated, and cleaned up the discussion of the
Lorentz force law here:
  http://www.av8n.com/physics/maxwell-ga.htm#sec-lorentz

At one point it says:

>         A field bivector in the plane of the paper
>         leads to a cyclotron orbit in the plane of the paper.


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