On Feb 11, 8:32*pm, Bob Engelhardt wrote:
Cross-Slide wrote:

Youtube video, for the electrical types.

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

Experiencing that as a video is really frustrating! *I want to ask Prof
Lewin questions, I want to see the connections, I want to try changing
them, etc. *Is one scope connected across R1 & the other across R2, with
lengths of wire between? *I think. *And that wire has voltage induced in
it. *(Am I able calculate the effect of that? No.)

As someone else said, the scopes cannot be literally connected to the
same points. *A mind experiment comes to mind :-) - a scope on the left
connected to *points* A & D and one on the right also connected to A &
D, as P. Lewin *implies*. *Now I switch them by leaving them connected &
simply moving them. *Do the displays change? *Obviously not. *What makes
the displays different? *That the scopes are not literally connected to
A & D, but across the resistors.

Bob

The scopes are literally connected to points A and D.

Think about This mind experiment...
You have two resistors connected in a ring around a ( tree for the
sake of visualization) When you are looking at the south resistor, on
the south side of the tree, and current is flowing through the
resistor, The East point is Positive and the west point is negative.

Since the current is flowing around the ring..
As you look at the North resistor, on the north side of the tree, the
West point is positive, and the East point is negative. It HAS to be,
since the current is still flowing in the same direction..

The EXACT SAME TWO POINTS are either negative or positive depending on
which side you stand as you measure them.

Your whole life you have analyzed circuits that had a "point
source" ( for lack of a better description) of power, either a voltage
or current source.

What the professor showed was how NON-INTUITIVE it becomes when the
power ( voltage or current source) is distributed along the length of
the circuit.

The professor did an amazing job of getting some people to think, and
others to deny what they are seeing.
Just like he warned at the beginning, and I warned in the title.
The deniers reacted with some hostility, and refuse to consider the
alternate way there might be to analyze a circuit.

Someone suggested that the circuit switched from a parallel to series
circuit.
Well, with only Two elements, ( two resistors) it is either or both
series and parallel.
Since the power source is distributed around the circuit, it is not a
separate circuit element.