Faraday Disk Generators and Pancake Coils

[PhysicsProf]

  The original generator was invented by Michael Faraday in 1831, the Faraday Disk Generator (fdg) -- see attached.  Along comes Tesla in the late 1800's with his bifilar pancake coil (bpc).

  Its time IMHO to do a little math here:  fdg + bpc = ?  .    In short, replace the disk with a bpc (try for comparison a uni-filar coil upc).  I suspect I'm off on a tangent again, but having fun - which I think is important, along with being observant.  I plan to use a strong ring-magnet, rather than the horse-shoe-shaped magnet shown in the old drawing (from the 1800's).

Please guess:

1.  Will it work, fdg with bpc?
2.  Are external "brushes" (stationary in the lab frame of reference) necessary for function?  
3. Or can the spinning coil transmit energy wirelessly?
(See flat coils by Slider in photo - now on my bench.  Thanks again, Slider!)
4.  Will an LED light if the LED is hooked to the spinning pancake coil, with a simple JT so it will run at lower voltage (from the fdg)?
5.  Spinning a uni-pc versus a bi-pc -- will one "work better" than the other?  measurably better?

My guesses:
1.  Yes
2.  NO -- and this violates some predictions IIRC.
3.  Yes
4.  Yes
5.  Predicting the bpc will work better than the upc.

[Slider2732]

Ah I see where this is headed now...I think  

What's confusing is the ring magnet compared to the horseshoe magnet.
I'd like to see the ring magnet design, because i'll replicate that for sure with the microwave magnets here

The horseshoes fields are free at the two poles on opposite sides of the coil (copper disk), whereas in a ring magnet they are on the top and bottom.
What would be equivalent, would be 2 ring magnets connected on a shaft, either side of the coil. That would simulate the horseshoe. The 2 ring magnets would give a larger surface area to work on a BPC. However, most flux is at the very centre of a BPC.
Hmmm, if both ring magnets were facing with same poles inward they would fight each other. Would a pseudo Bloch Wall be created at the point of the spinning BPC ? That one has me very interested indeed...to use the zeroing energies of that area. It may not be a Bloch Wall of course and I may be talking out of the proverbial posterior
OR, at a very fast RPM. the shaft could be removed from the BPC and it sits there spinning, levitating away and locked by the magnetic anti-gravitic forces! or not.


1. I can see it working with a UPC, if the windings are very tight and very many.
2. Brushes 'should' be needed, but who has tried without and by another means ?
3. Good question, no idea !
4. If Faraday created a voltage, he also collected more than uA one would imagine. A detectable voltage probably copper disk size related.
5.The single winding would be expected to produce a similarity to the copper disk...but is it Eddy forces, or is it an induced voltage by some other means that a coil could collect ?
The BPC may throw up a surprise, the UPC would be the fave though for initial results, if some kind of Eddy current isn't the reason for the produced voltage.

[PhysicsProf]

  I appreciate your musings, Mark.

  AT heart, I guess I'm an experimenter and like to try novel things.  Here: replacing Faraday's spinning disk with a spinning BPC or UPC.  First, does it work to generate a voltage, with brushes?  What if we put a Ge diode in the wire, will that help?  (something one cannot do with a conducting disk, Faraday used copper)

Second,  does it work to generate a voltage, withOUT brushes? (scientific papers have said "NO", IIRC)
  that is, one has to measure for voltage-generation ON the disk somehow (no brushes to contact the outside world).

Lots of things to try... to experiment with.  I always like to look for the "anomalies". 

[PhysicsProf]

What if we put a Ge diode in the wire, will that help?

With the diode in place, one can add a cap in series... then measure the voltage on the cap AFTER stopping the spinning...

[PhysicsProf]

OK, here's the expt I've been working up to.

Another strange one IMO -- an experiment I came up with, charging up a cap through a Schottky diode by SPINNING a ring magnet over a bpc... enjoy "Faraday's Paradox Revisited" --

http://www.youtube.com/watch?v=I3hXYSKxsX0&feature=youtu.be


"Way back in 1831, Michael Faraday invented the first electrical generator, spinning a conducting disk in a magnetic field. A voltage was generated between rim and axle of the disk. But spinning the MAGNET does NOT produce a voltage. This is "Faraday's paradox" in a nutshell and has stood for over 180 years.

But wait -- here I spin a ring magnet and 100% repeatably observe a voltage rise... in an experiment I devised to further test Faraday's paradox... Pls see the video of my little experiment. Note that I replace the conducting disk with a bifilar pancake coil (BPC) wound with coax. Charge from the coil is collected through a Schottky diode on a 47 uF capacitor which held at zero mV for an extended time prior to the experiment."

[PhysicsProf]

No words video...

http://www.youtube.com/watch?v=0kC6geb3OAk&feature=youtu.be

Video shows effect of moving the ring magnet over a compass-- how the compass is affected. But spinning the ring magnet over the compass, no observed effects. That surprised me; I don't think its just inertia in the compass.

Yet spinning the same ring magnet over a bifilar pancake coil results in a charging of the cap connected to the coil (through a Schottky diode). Repeatable 100%. This time, from zero to about 1.3 mV on the cap.
BTW, holding the magnet over the coil without spinning does NOT result in charging of the cap.
Faraday's paradox? hmm....

[PhysicsProf]

  Further expts and some frustration -- at the few-millivolt level, the cap can register increase in voltage just touching the BPC...   I think it may be picking up energy from the "air" -- radio, grid noise, etc.   Anyway, I'm a bit frustrated with this particular device and will be looking at something with HIGHER power levels.