Lewin's NCF Experiment and Lecture

[tinman]

Tomorrow i will set up this experiment.
I will place 1 scope probe directly in the middle of the secondary turn with the resistors in place,and so the scope probe and ground lead go directly over the top and at the center of the coil.
I will dump the energy from a large cap into the coil,and keep increasing that caps stored energy amount until i get an EMF of 1 volt on the scope.

Then we can start changing scope probe positions,and see what happens every pulse.


Brad

[poynt99]

I think the problem here lies within the measurement device leads them self-circled in red,where they set up there own loop that the electric field from the solenoid acts upon.
CH1,and CH2 should read the same.
Just my thoughts.

Brad

Yes, the measurement leads are part of the experiment in these configurations, therefore should they read the same voltage?

[tinman]

What voltage will the left meter indicate?

Well if there is any sense to this at all,it should read minus 100mV,as there is no voltage drop (or very little) across the conducting wires between the resistors.
But in saying that,it could just as easily read minus 900mV,as it's at the same measuring point as that that read's 900mV.

Will find out tomorrow for sure though.


Brad

[tinman]

Yes, the measurement leads are part of the experiment in these configurations, therefore should they read the same voltage?

No.not until current starts to flow through the single loop/resistor combo.



Brad

[poynt99]

Tomorrow i will set up this experiment.
I will place 1 scope probe directly in the middle of the secondary turn with the resistors in place,and so the scope probe and ground lead go directly over the top and at the center of the coil.
I will dump the energy from a large cap into the coil,and keep increasing that caps stored energy amount until i get an EMF of 1 volt on the scope.

Then we can start changing scope probe positions,and see what happens every pulse.


Brad

With an induced emf of 1V, would you expect your decoupled measurement (vertical leads) to measure 1V between points D and A as you have shown?

(it won't be)

Here is how you "calibrate" the experiment: if your scope ground lead is long enough, simply loop it around the solenoid and clip it to the probe tip. If it is not long enough, add a piece of wire. Set your scope to 200mV/div and start discharging your source cap at different voltages until you get a peak of 1V on the scope.

You have now measured the E field and set it to induce 1V into the secondary circuit.