Re: EM Induction - A conceptual question

["John S. Denker" <jsd@MONMOUTH.COM>]

Chuck Britton wrote:
> except along the side that is IN and PARALLEL to the B field. THIS is
> where the non-zero contribution comes in.

OK, sorry, I was imagining a different orientation for
your loop.

> Carl seems to have it
> right. There  must be a fringing field to cancel it.

Yup.

> DOES this fringing field affect the original question?
> I don't THINK so.

I don't think so, either.
And you don't even need to have a fringing field at all.
Just run a long solenoid (flux _and_ windings) down the
middle of the other ring, to create a region of constant
field surrounded by a region of no field inside the ring.

==================

While we're on the topic of fringing fields:

1) We are all familiar with the notion that the field
inside a long solenoid is uniform.  This is mostly true.

2) There is a widespread misconception that the uniform
field extends all the way to the ends, so that the flux
lines shoot straight out the end like water shooting out
of a garden hose.  This is not right.

You can easily show (by symmetry!) that the field right
at the end of long solenoid is half the strength of the
field at a typical point not near the end.  That means
that half the field lines have "leaked out" sideways
before reaching the end.  There's a whole lot of fringing
going on.