On 2/14/2010 11:07 PM, Don Foreman wrote:
On Sun, 14 Feb 2010 22:22:41 -0800,
wrote:

(...)

Good! That means you grok Ohms Law which states we cannot expect
large voltage differences on the ends of a good conductor
that is passing Very Little Current.

You demonstrated quite the contrary with your experiment.

No, in my first experiment, I was not able to determine any voltage
difference across the wire connecting the top of R1 to the top of R2.

When I saw the maximum voltage in my 2nd experiment, it was being
dropped across a ~22.8 K ohm resistor. Current was on the order
of 5.3 uA, so I did not expect to see measurable voltage drop
across ~1.5" of an 0.022" diameter wire (tens of nano Henrys?).

X(L) for say 50 nH at 60 Hz is what, 19 micro ohms?
I'd need a meter that could resolve femtovolts while nulling
out millivolts. I sure wasn't going to see the 1.0 V difference
predicted by the Prof.

That wasn't the proper place to look anyway, as the prof had indicated
that the two voltages in question were dropped across R1 and R2.
If you isolate the top of R1 from the top of R2 you will see that
they *do* have different voltage drops and they *are* 180 degrees
phase displaced. His circuit shorts the 'meters' together which
completely obliterates the appearance of these differences, however.

Induction can produce a voltage difference from end to end of a
good or perfect conductor regardless of what current it may be
passing.

Yes, and in my experiment, that voltage difference across the
entire winding was about 120 mV, open circuit.

Ohmic IR drop is independent of induction and superposition holds.

Yes! With R1 and R2 connected together as in the Prof's 2nd
circuit, the voltage across R1 was summed with the voltage
across R2 to yield a single voltage value. When R1 equals R2,
the voltage dropped across them both sums to a value that is
very nearly zero because of phase cancellation. In my second
experiment, I showed that 5.3 uA through a 11.35K ohm resistor
can appear to have a voltage drop of very nearly zero (a
great deal less than 60 mV) if it is connected with another
11.35K ohm resistor that is also passing 5.3 uA from the same
source, but in the opposite direction.

That is what I have been on about.

--Winston