Re: induced emf again

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

Bob Sciamanda wrote:

> ... c) It happens that these two distinct effects result
> in an emf which, for many circuits, can be calculated
> by the flux rule emf = - dPhi/dt.
>
> Read Feynman Vol II 17-1 and 17-2.  RPF points out
> that the flux rule is a not completely reliable calculational
> tool and (when it does work) only gives you the resulting
> emf, not the underlying physics. ....

After reading Bob's messages I am accepting Feynman's
idea of two distinct effects. The original question should
have been asked in this way.

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.

Why are the "two distinct phenomena" not recognized
in our introductary textbooks? Why don't we have two
distinct names for two distinct phenomena? Would it
be better to say that  "motional emf" is different from
"induced emf?" How come that both emfs can be
calculated by the same formula? Only a coincidance?
Ludwik Kowalski