Re: EM Induction - A conceptual question

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

Chuck Britton wrote:
> I choose an amperian loop to be a rectangle, one side within
> the field and parallel to the field, opposite side,  parallel to the
> first but in the field free region, and the two connecting sides at
> right angles to the field????
>
> How much current passes through this loop? It SEEMS to be a problem!

Repeat after me:  Voltage equals flux dot.  Voltage equals flux dot.

1a) Calculate how much flux there is inside the loop (rectangular
or otherwise).
1b) Calculate how fast this flux is changing as a function of time.
That gives the induced voltage around the loop.

2) Calculate the resulting current using Ohm's law.
This is easy if it's not very much current.

If the current is large, you need to redo step 1 because
        voltage = TOTAL flux dot,
including the flux created by the induced current.
Including the induced current gives one more equation in one
more unknown.  The new equation is particularly simple if you
know the inductance of the loop, because flux = inductance * current.

Collecting ideas:
        voltage = flux dot
        flux = external_applied_flux + loop's_induced_flux
        loop's_induced_flux = inductance * current
        current = voltage / resistance
which is four equations in four unknowns.
Not very hard to solve.

If this isn't the answer, please clarify the question.