Lewin's NCF Experiment and Lecture

[tinman]

OK,here we go.

All tests at each point were done 3 time's,and results are all the same in each of the 3 tests.

Below is the modified circuit,so as the top lead out of the coil now go's down the center of the coil,and twisted with the bottom lead in of the coil--as pictured below. I have twisted it as much as i can-right to the switch,as the wire is very thick,and the coil it self is square shaped ali insulated single strand wire-->more like rod.

So for this post,i will show a picture of the setup now,and a scope shot of the scope probe looped around the coil at the center--so as you can see we are close to the required 1v potential--thats as high as my PSU go's in voltage-31volts,so as close to the 1 volt potential as i can get with this coil.

In my next post,i will supply a scope shot taken at each point indicated in the schematic.
Poynt--you better dust of the old setup


Brad

[tinman]

below are my test results for each supplied schematic.
Please note the VPD on each scope shot,as i change them as required in relation to voltage potential reached for each test position.

It is clear from my test,that as i stated before,the potential across both resistors should be the same,and that the scope's probe and ground lead is what influences the result,s.
It is also clear that the voltage potential across the wire(which should be 0),is as high(if not higher) than the potential across the 100R resistor.

All test were carried out with the scope probe and ground lead loop in the horizontal plane to that of the resistors loop.

Brad

[tinman]

A close look at the results by separating the scope shot's.
By looking at two at a time,we get a clearer idea.
40mV across R1,and 40mV across R2

Brad

[tinman]

And the other two scope shots
A clear indication that it !is! the scope leads loop position that determines the voltage potential seen on the scope,and not the actual potential across the resistors--as i said before,should be the same.
500mV across R1,and 500mV across R2

Brad

[poynt99]

It is clear from my test,that as i stated before,the potential across both resistors should be the same,and that the scope's probe and ground lead is what influences the result,s.

Good. It still seems something isn't quite right as even though you have 1V emf, you don't have 1V total across the resistors, correct? Is that wire fairly low resistance? Is it ferromagnetic? You are only getting about half the voltage. Aren't you wondering where the other half is? I'm guessing your wire is highly resistive (which would also explain why you're measuring a voltage across the wire when you shouldn't). I used wire from 14/2 house wiring, so it is good old solid copper.

Does it surprise you that the scope measures the same regardless of the probe position?

What does it mean when you have one probe on the left and one probe on the right measuring across the same resistor, but are getting two completely different results? That brings us to the end of Lewin's demonstration and lecture basically. Congratulations, you have replicated the experiment. Ready for perspective two?

It is also clear that the voltage potential across the wire(which should be 0),is as high(if not higher) than the potential across the 100R resistor.

I'm going to verify this with my setup. Again, if the wire has a low resistivity relative to the resistor values, you should measure very little across the wires.