Re: induced emf again

[Ludwik Kowalski <kowalskiL@MAIL.MONTCLAIR.EDU>]

I should have added that the suggested experiment (see
below) should be performed twice: (a) when the rod is
sliding in a constant magnetic field and (b) when the
rod is stationary but the magnetic field is changing. In
the first case the direction of E inside the rod will be
opposite to the direction of conventional current, in
the second the two directions will coincide. If not
then the idea of "two distinct effects" would remain
a hypothesis. I am saying this because I am not
aware of experiments in which the two directions
were compared. Please share what you know.

Ludwik Kowalski wrote:

> ... Here is another suggestion. Use a voltmeter to
> find out about the direction of E lines inside the rod,
> use a galvanometer to determine the direction of the
> current. The wires leading to the voltmeter should
> be parallel  to the magnetic field lines.

> > Consider a metal rod of length L sliding with the
> > speed v along the rigid U-shaped wire frame
> > perpendicular to the uniform magnetic field B. Do
> > the electric field lines INSIDE THE ROD have the
> > same direction as the conventional current? My
> > answer, especially after the discussion about the
> > induced emf we had last winter, would be "yes."
> > But now I think it would be a wrong answer. I
> > now think that the electric field inside the loop
> > is conservative, all electric lines begin and terminate
> > on static charges. In other words, the sliding rod
> > behaves as if it were a battery whose emf is B*v*L.
> >
> > The origin of my misconception is probably rooted
> > in the rule according to which "the way in which the
> > flux changes is not at all important, it can be a
> > stationary B but changing area, or it can be a constant
> > area but changing B." But Faynman argues that two
> > ways of changing the flux result in two different
> > phenomena. Right or wrong? I wish I could refer to
> > an experimental verification of this theoretical claim.
      Ludwik Kowalski