Re: [Phys-l] Magnetic force and work

[John Denker <jsd@av8n.com>]

Bob Sciamanda wrote:
> 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.

I agree;  fixed now.

> 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.

Six of one, half-a-dozen of the other.

I chose to take the viewpoint that the particles were _free_ particles
moving _freely_ inside the wire, except when they smack into the force
of constraint.

I added a parenthetical remark clarifying this point.