Lewin's NCF Experiment and Lecture

[minnie]

Johan,
         yes,you've got me Sussed out!
   I'm crap really at this sort of stuff, just look at what happened to
  my latest little project. I put it on test and went to work and when
  I came back there was a dreadful smell. Luckily I didn't burn the
  place down.
      Over the years not that many who contribute to this forum have
   a good grasp of measurement techniques (only my opinion). Just
   look at the Rosemary Ainslie saga.
       Someone could do this Lewin thing with a bit of paper and a pencil
   I'm sure. I just wish I could do that sort of thing.
               John

[poynt99]

What were you building there, and why did it go up in smoke?

[tinman]

It would appear something is not sufficient in your setup. You should not be measuring a voltage between the wires, or at least very little.

Well as there are only two resistors,and two short pieces of copper wire joining the two resistors together-where that copper wire is the same diameter as the resistors wire,i am not sure what could be insufficient in the setup?.
Did you try and measure a voltage across the wire it self when you were testing your setup?.

In regards to your question, I'm not sure what you are asking. Do you want to know why the 100 Ohm resistor shows a negative polarity while the 900 Ohm shows a positive polarity? Is that what you are asking?

No.
I mean,when the ground is fixed in position as marked in the schematic below,and the probe is on the other side of the 100R,i get a negative voltage spike across the 100R. We then leave the ground where it is,and measure across the wire it self-along the bottom wire that joins to the 1KR,and we still get a negative spike to the very same value as seen across the 100R,and yet the probe is now on the leading side of the current flow to that of the ground of the scope.

There has to be a voltage drop across the wire's,as if there was not,then at any point along the two wires,the potential difference must be the same,and there for the same on either side of each resistor.
There is also the fact that we are measuring current flow,and not just the electric field,as we can clearly see an overshoot in all the scope shots-caused by the collapse of the magnetic field when the cap has drained.

It would seem to me that the seen voltages are a result of the loop in the measuring equipment and resistors them self,and not an actual measurement of a voltage drop across the resistors/ loop.
If there is not suppose to be a voltage seen across the wire itself,then how is there a difference in potential from one end of the two wires to the other?,which will be across each resistor.

Im going to take a guess here,and say that i believe if i measure across the top wire in the circuit,i will see the same voltage as across the 1k resistor. But i will have to change the position of the coil on my setup,as i cannot fit the scope probe between the backing board and coil when the scope probe and ground need to be on a horizontal plane.

Each scope shot below was taken with only 1 scope channel hooked to the circuit.

Perhaps you should dig out that old setup of yours Poynt,and scope across the wires them self?.



Brad

[poynt99]

Well as there are only two resistors,and two short pieces of copper wire joining the two resistors together-where that copper wire is the same diameter as the resistors wire,i am not sure what could be insufficient in the setup?.

You said you had to reposition the probe somehow while measuring the 100R in order to get a voltage reading if I'm not mistaken. You shouldn't have to do that. That is a sign of one potential problem. You also have not taken care to minimize the effect from the source wiring. Take a close look at mine and you will see what I did. The only horizontal wiring  is twisted to cancel the "stray" magnetic field. The top conductor of the solenoid travels down the inside so it can exit at the bottom, twisted with the other end.

Did you try and measure a voltage across the wire it self when you were testing your setup?.

I'm fairly certain I did, but it was a few years ago and I could be mistaken.

There has to be a voltage drop across the wire's,as if there was not,then at any point along the two wires,the potential difference must be the same,and there for the same on either side of each resistor.

If you look back at my diagrams, I show three probe positions for the meter on the left. What are the meter voltages at each of the three positions?

If there is not suppose to be a voltage seen across the wire itself,then how is there a difference in potential from one end of the two wires to the other?,which will be across each resistor.

Same response as above.

Perhaps you should dig out that old setup of yours Poynt,and scope across the wires them self?.



Brad

Yes perhaps I will. Tell me what you measure at those three positions first.

[Johan_1955]

Johan,
         yes,you've got me Sussed out!
   I'm crap really at this sort of stuff, just look at what happened to
  my latest little project. I put it on test and went to work and when
  I came back there was a dreadful smell. Luckily I didn't burn the
  place down.
      Over the years not that many who contribute to this forum have
   a good grasp of measurement techniques (only my opinion). Just
   look at the Rosemary Ainslie saga.
       Someone could do this Lewin thing with a bit of paper and a pencil
   I'm sure. I just wish I could do that sort of thing.
               John

Hi John,

Maybe to take it to: http://overunity.com/15158/food-for-thought-our-world

Out of respect for TM and .99.

Regards, Johan