Lewin's NCF Experiment and Lecture

[poynt99]

For the resistor circuit I used the solid 14/2 copper wire, stripped.

For the solenoid, I used jacketed 14 GA stranded AC wire, but solid may work fine as well.

Surely you agree the sum of 500mV and 40mV is 540mV? That is the voltage across the resistors. You should have 1V across the resistors, agreed?

So yes, as I have been saying, there is a problem with your setup. But in the conceptual sense, you are still getting the experiment correct.

[tinman]

For the resistor circuit I used the solid 14/2 copper wire, stripped.

For the solenoid, I used jacketed 14 GA stranded AC wire, but solid may work fine as well.

Surely you agree the sum of 500mV and 40mV is 540mV? That is the voltage across the resistors. You should have 1V across the resistors, agreed?

So yes, as I have been saying, there is a problem with your setup. But in the conceptual sense, you are still getting the experiment correct.

I would like to get it to be exact.
So first i/we need to find out why i am seeing a higher voltage across the resistor joining wire than i am across the 100 ohm resistor.
I am keen to see if you measure a voltage between your two resistors,across the wire.


Brad

[poynt99]

I would like to get it to be exact.

Good.

So first i/we need to find out why i am seeing a higher voltage across the resistor joining wire than i am across the 100 ohm resistor.
I am keen to see if you measure a voltage between your two resistors,across the wire.


Brad

I do and I don't.

I do if I measure with a "flying" gnd lead.

I remembered however (its been a few years) that since we're dealing with stray magnetic fields and at least a thousand to one resistor to wire resistance ratio, in order to get an accurate reading for the wire segments, I had to solder two pieces of wire onto the wire so the two could closely follow the circuit wire and be brought out to the middle and probed there. See the illustration. Measure it like that and you should see very little voltage across the wires.

With 32VDC on the cap, I get 400mV peak emf (calibration step with scope probe only), then about 360mV across R2, and -40mV across R1. With 0V across the wire segments, all measurements are as expected and the tally adds up perfectly.

[Artoj]

Just to be sure we don not mix, schematics(abstract) with actual wiring.  I hope this helps, the values are guesses only. Regards Arto. 

[poynt99]

We're not quite there yet, but thanks for the diagram.

I already have a diagram prepared, which is coming next with the discussion of perspective no. 2 (once we get over this wire segment hump).