On Tue, 18 Mar 2008 14:13:13 -0700 (PDT), Half-Nutz
wrote:




And to illustrate just how confusing this sort of thing can be...
Here is a lab demonstration from MIT, that WILL blow your mind, if
you follow it, and all of it's implication. It blows Kirchoff right
out of the water. ..

http://youtube.com/watch?v=eqjl-qRy71w

Watch both parts of this demo. Prof. Levin is really amazing.... Look
for the rest of his lectures.

This guy is more performer than docent. Kirchoff's law does not
presume lumped sources of EMF, it states merely that EMF's and drops
in a closed circuit or mesh sum to zero.

It is true that many engineering texts present circuits (and
Kirchoff's law) with lumped EMFs, because in real circuits that is
most often the dominant case.

At one point in his lecture he leads (or at least allows with a bit of
nudge) his "audience" to think that the induced EMF should be thought
of as being lumped at the location where the battery was, which of
course is false. Later he shows a line integral suggesting that the
EMF is indeed distributed, but he still prefers to discredit Kirchoff
in favor of Faraday. The line integral of induced EMF around the
circuit or mesh would and does indeed equal the former battery EMF.

He may be a great mentor for academists, perhaps not for engineers.