Re: First Law (now perpetual motion)

[Herb Schulz <herbs@INTERACCESS.COM>]

At 10:28 AM -0500 on 1/24/99, Herbert H Gottlieb wrote:
> I know that it won't work, but I wonder if your explanation of WHY it
> won't work is correct....... .......????
> If we connect a long wire to the terminals of a galvanometer and then
> move a small section of this wire between the poles of a horseshoe
> magnet,
> the wire cuts magnetic lines of force and induces a current in the
> galvanometer.
> Similarly, if a small section of a wire is stretched from wintip to
> wingtip
> of an airplane and the rest of the wire is covered by magnetic shielding,
> we should have the changing flux through the loop that you say is
> necessary.
>
> Herb Gottlieb from New York City
> (Where the earth's magnetic flux lines are essentially vertical)

Howdy,

Notice that I didn't say anything about "cutting magnetic lines of force."
I said that there must be a changing flux through the loop.  Pulling one
part of the loop through a region with a non-uniform B-Field will change
the number of magnetic lines that pass through the enclosed area of the
loop, i.e., change the magnetic flux through the loop.

I've also gotten to dislike Electric and Magnetic Field Lines being called
Lines of Force.  Students begin to think that there is a force on a point
in space which couldn't be further from the truth.  There will be a force
on a charged particle placed at some point in space (if E isn't zero at
that point) or on a charged particle moving through a point in space (if B
isn't zero at that point) but there is nor force at or on the point itself.

Good Luck,

Herb Schulz
(herbs@interaccess.com)