Faraday's Paradox -- the Homopolar Generator Puzzle

[PhysicsProf]

   While traveling, I've been thinking about the Homopolar Generator -- which gives rise to Faraday's Paradox.

See photo:  rotating conducting disc (e.g. aluminum) with magnet(s) providing B perpendicular to the disk-face.  Voltage seen from axis to edge-brushes -- when:

1.  magnets stationary  and disc is spinning;
AND when
2.  magnets attached to disc, co-spinning.

NO voltage seen when:
3.  disc stationary and magnets spun.

Thus, there is an apparent "paradox" vis-a-vis relativity, maybe.  See fig, and http://en.wikipedia.org/wiki/Faraday_paradox

My question -- will a capacitor charge if ATTACHED to outer edge of disc, and other wire to the central axis -- with magnets attached to disc, all co-spinning ?

[Slider2732]

My understanding....

If Faraday knew that magnetic fields will remain stationary, when an axially magnetized magnet is spun, then he'd have no paradox.
Here's an old video from 2009 by AdminOnDuty, which shows the phenomena: http://www.youtube.com/watch?v=rWO7O5hvzWE

Apparently, Bruce De Palma's 'N Machine' operated with this understanding. Rules and laws don't account for static forces in a moving magnetic object, or at least for Faraday they didn't. You can spin a magnet at 90 degrees and witness what is expected, but not along it's axially magnetized direction. There are some potentially incredibly powerful phenomena to be explored with that understanding and, presumably the 'N Machine' made fine use of that knowledge.

If we look at the charging of the capacitor, the field has to interact with the electricity, to cause a reaction, which is displayed as a charge upon the capacitor.
Here we step into Ed Leedskalnin's boots - Both electricity and magnetism are the same thing - at a molecular level and deeper, we and everything around us are built from magnetic forces, bond formations based upon the characteristics of different elements...what keeps an electron in orbit ? why does the Earth have a lock of orbit ? - big, small, fast, slow.
Being the same thing, both will appear to interact, one will display characteristics of the other. One is present when the other is present.

All is counter intuitive, based on regular schooling. If we spin something, we expect whatever forces it displays to spin too. How odd it would be, if when spinning a standard metal rotor the middle didn't turn but the outside did. Well, if we cut a ring just inside the perimeter of that rotor, fit a ring magnet to the inside edge and a ring magnet to the other side of that edge, we then fit magnets to the circumference and we can have exactly that situation. A perfectly fine running rotor is the result, with no moving middle.
That is what happens with the lack of energy produced to charge a capacitor with a spinning magnet.
All may turn, all may seemingly interact and all, should, produce an electromagnetic effect that we would expect to charge the capacitor - but it doesn't. The magnetic field stays put in the spinning magnet, a non moving, special characteristic, as very nicely displayed by using a CRT screen in the video above
However, if a piece of magnetic material is added to the side of such a magnetic, then the imbalance will cause the flux to behave as expected...inducing a charge on the capacitor, relative to the strength of that attached piece.

Could be very wrong and i'm all ears for rebuttal

[poynt99]

My question -- will a capacitor charge if ATTACHED to outer edge of disc, and other wire to the central axis -- with magnets attached to disc, all co-spinning ?

Yes. There is a conductor moving through a magnetic field, therefore an emf will be induced and the cap charged.

I don't see a paradox with this experiment at all. Each condition and the resulting outcome makes perfect sense.

Does everyone here agree?

.99

[PhysicsProf]

Yes. There is a conductor moving through a magnetic field, therefore an emf will be induced and the cap charged.

I don't see a paradox with this experiment at all. Each condition and the resulting outcome makes perfect sense.

Does everyone here agree?

.99

   Thanks for this prediction, but as for me, I need an experiment to see what happens.  I do think that the result you predict has serious problems vis-a-vis theory of relativity...  but this I would explain later.  It involves a linearization of the rotating disc + magnet + cap -- think first of a very large radius system.

For the experiment, smaller disc sill do, and  I would add a diode in series with the cap so that it will HOLD the charge -- so one can stop the disc and measure any built-up voltage on the cap easily.

Thanks for the comments...   Where can I get two STRONG ring magnets?  roughly 4" (10 cm) diameter?

[PhysicsProf]

  I have just a minute ...

So now, go from disc to a rectangular conductor, say 20 cm long by 4 cm high, with strong magnets glued on, B perpendicular to face of conductor.  Cap from bottom to top. 

1.  Move with this.  Will charge appear on cap?  If so, you can tell you are moving, absolutely, violating relativity.

2.  Earth is already moving, so, keep device stationary on earth.  Will charge appear on cap?  If so, you can tell earth is moving, absolutely, violating relativity.

[poynt99]

  I have just a minute ...

So now, go from disc to a rectangular conductor, say 20 cm long by 4 cm high, with strong magnets glued on, B perpendicular to face of conductor.  Cap from bottom to top. 

1.  Move with this.  Will charge appear on cap?  If so, you can tell you are moving, absolutely, violating relativity.

2.  Earth is already moving, so, keep device stationary on earth.  Will charge appear on cap?  If so, you can tell earth is moving, absolutely, violating relativity.

For me, I would need a drawing of what you describe, and more details of what it means to "move with this".

[Slider2732]

Yeah, a drawing would be good. I'll include myself in any builds to come forward.
These type of motors don't take long to make and it would be fun to find out.
It's how you want the geometry and connections.

[PhysicsProf]

Please see the first post for the drawing of the usual Faraday homopolar generator, and the photo.  Two ring-magnets, one on either side of Al disc, field B through the disc, perpendicular to disc face.   Microwave magnets, IIIRC.

My change (see photo) is simply to solder a (cap + diode) to the axis and other wire to the rim, where the brushes are seen in the photo.

[poynt99]

 I have just a minute ...

So now, go from disc to a rectangular conductor, say 20 cm long by 4 cm high, with strong magnets glued on, B perpendicular to face of conductor.  Cap from bottom to top.  

1.  Move with this.  Will charge appear on cap?  If so, you can tell you are moving, absolutely, violating relativity.

2.  Earth is already moving, so, keep device stationary on earth.  Will charge appear on cap?  If so, you can tell earth is moving, absolutely, violating relativity.

I think you misunderstood Steve.

The request for a drawing or more detailed description was in reference to the above quote. What you are proposing is not 100% clear.

.99

[PhysicsProf]

  OK -- stopped for the night at motel (past midnight, but what the heck).  Did drawing, and posted side-by-side with disc version also.
DISC -- contacts stationary in lab, made at outer edge and at axis.  For my modification, a cap + diode would attach one wire to rim (=outer edge) and one wire to axis, so these contacts are attached to the spinning disc.

Now -- cut that disc in half, and "bend it" (transform) to a bar.  Magnets on both sides, B field through the conductor in BOTH cases.
BAR -- contacts stationary on top and bottom of the bar.  One can move the bar + magnets + caps + diodes, as I stated before.

I put in TWO (cap+diode)s -- so one can see how the two caps compare.   IF a charge appears on either cap (or both) when the bar is moved -- or when the earth rotates (day to night) -- this would be a VERY interesting result.   For example -- in that case of charging cap -- where does the ENERGY come from??

PS -- I'm far from home... Is anyone interested in setting up and testing EITHER experiment?  the disc version and/or the bar version?  with cap + diode, that's essential.

--Steve

[Slider2732]

I've not the copper, or what seem to bar magnets (?) for this, but, will have a go at something at least tomorrow
Been moving back to my regular livingroom table from the bedroom and sorting through stuff as I go, so a few things have been paused.

Homopolars with the two posts and coil of wire, or screw hanging from a battery are 10 minute build things, this one seems quite a bit different.
If I look at it a few times I might get the idea.

*edit
Ahh, found the video where your screenshot came from Steve: http://www.youtube.com/watch?v=75p5JwlXwlo&feature=fvsr

Also found a good free running aluminium rotor with a magnet around the edge, but the feeling is it's not what's required:

[PhysicsProf]

"I've not the copper, or what seem to bar magnets (?) for this,
"

Aluminum is fine instead of copper.  Bar magnets for the bar version, but with poles such that B is INTO the face of the bar.  North on the one face, then aluminum bar, then north on the other bar magnet on the far side.

North (outer) -> South (inner) -> then aluminum/copper bar -> north -> south.
 Same thing for the disc version.

Thanks Mark -- keep up the good work!   (This is one thing I dislike about traveling -- I can't do experiments for a while!  sigh  But I did bring some things once we settle.)

[PhysicsProf]

  More thought on this....  and a simple experiment.

A conducting disc or squarish plate is OK, too, with STRONG magnet on one side -- or both as shown in figure.  Copper or aluminum is fine.
Cap + Diode, to collect charge and HOLD charge long enough to measure when you "stop" the thing; attached on either side of the strong magnet(s), as shown in figure.

Mount 1st on a wheel near outside rim; discharge cap; spin wheel fast for a minute;  stop and check if any charge on cap.  That's all for this important first experiment with co-spinning cap on a metal plate + strong magnet.

Anybody willing to try this?  I'm glad to kick in $200 each to two guys who will give this a go while I'm "stranded"  away from my lab!  don't feel sorry for me being out here babysitting; if you need a little boost, pls just do the experiment.  I'm very curious about whether a charge will appear or not.

[Slider2732]

It shouldn't cost $200  
Mind you, depends what you've got planned after the first test lol. Heck, for $200 i'd do an evening of babysitting too !

OK, i'm in
Today was a bit of an off day for builds, Julie and I have been married for 5 years (caught the last March 21st Equinox in 2007, for quite some years ahead)
But tomorrow i'll see if there are any magnets here of strength, that are not on Bediini wheels. Hmmm, maybe dismember one of those. Will also see about a better and larger rotor, that is not on a Be...yeah, I think you see where i'm going here.

[Slider2732]

Very confused here, about the motive power of the homopolar motor.
I've found another video which may link with your thoughts Steve - http://www.youtube.com/watch?feature=endscreen&NR=1&v=XSWwrvT_c8w
But, again it's not powering itself. He has a DC motor on the end of a shaft during his tests and that is spinning everything up. The original screenshot in the first post had a similar arrangement, powered by a spinning lathe.
So, I have no idea how the assembly is to turn itself and then be rigged out for the capacitor/diode test  
Also, i'm not seeing how the copper disc in the above video operates.....just all around confused.
What I can do, is emulate the above video, using the DC motor, if I knew what the copper disc did. He refers to brushes and yet where are they being used as brushes ? All of this is elementary, must be, but I don't get it  

So...
An alternative approach is something i am very familiar with. It was what I called  'Phase 2' back in 2010 and was a homopolar based on a regular brushed motor. You take the armature out of a regular DC motor, Connect 1 or 2 (of the 3) windings to the motor shaft on the other side of the commutator. This creates a physical connection to the shaft of the windings, but leaves at least one disconnected. Mounted on 2 conducting poles, with magnet below, the rotor spins up.
If I were to connect a copper/aluminium disc to the shaft, then that would form the homopolar motor and allow generator tests with the capacitor/diode.
Is that the direction to go and have I answered my own question ? lol


Here's a Phase 2.

[PhysicsProf]

Very confused here, about the motive power of the homopolar motor.
I've found another video which may link with your thoughts Steve - http://www.youtube.com/watch?feature=endscreen&NR=1&v=XSWwrvT_c8w
But, again it's not powering itself. He has a DC motor on the end of a shaft during his tests and that is spinning everything up. The original screenshot in the first post had a similar arrangement, powered by a spinning lathe.
So, I have no idea how the assembly is to turn itself and then be rigged out for the capacitor/diode test  

I'm not saying the disc needs to "power itself".  Using a motor to spin it is fine,  I expect that.

Let's not worry about this latest vid; I don't think it is helping (but rather is confusing).  Let's go back to the original video (see attachment).
Here you seem to be on the right track:

....
If I were to connect a copper/aluminium disc to the shaft, then that would form the homopolar motor and allow generator tests with the capacitor/diode.
Is that the direction to go and have I answered my own question ? lol

YES!   So let's go back and set up just as you say, with an Al disc on the shaft of the motor ( or lathe), with a ring-magnet on that would be best.

See how he holds the contacts for the meter reading, as "brushes"?  one of the brushes is a spinning contact, the other a straight probe -- this is fine.

Step 1:  replace the meter with a Capacitor + diode, and let's make sure the cap charges in this configuration as it must (based on the meter reading).  That is, start with the cap discharged to 0 volts, then run the device replacing the meter with a Capacitor + diode.  Stop the motor = stop the rotation, then measure the voltage on the cap.  It must be non-zero before we proceed.

Step 2:  The only change is to connect one wire of the cap + diode (in series, same direction as in step 1) to the axis, the other wire to the rim = edge (either by soldering or by a clip).  Again, spin the device using the motor, stop the rotation, and  then measure the voltage on the cap.  Is it zero or non-zero?    I see here a great difference between this (co-spinning) and the step-1 experiment (brushes, not co-spinning), and the result I cannot predict for certain.  It has to be measured by experiment.  In fact, I predict the cap will NOT charge in this case because charging in this simple system MAY violate a principle of relativity.  But I HOPE I am wrong = I hope the cap charges -- as a charging cap in this case would be more interesting.

Thanks!  

[Slider2732]

Looks like I might be over-engineering this then.
Started on something before I read your reply and so have paused, now that i've read it.

The idea, to make a homopolar, like the Phase 2 type and attach a disc to the output shaft. To use a standard DC motor would still necessitate the disc part, so maybe this is all just a bit more homopolar like than it may have been.
Well, I grabbed an old drill from the shed and took it apart.
Stripped out the motor and then Dremmel'd off the tabs at the back.
Removed the brushes section and Dremmel'd off the cog on the shaft front, to get the rotor out.
Then, built up a support assembly, based on a piece of slate, with copper stantions to supply the power.
At the moment, it's being powered by a 3.7V Li-Ion, but basically brushed...the windings need to be soldered up to the shaft, to run as a homopolar.

The pics show the disassembly and build up. The 3 elastic bands hold down the large'ish neodymium underneath
Speed of rotation at this point, with the piece of brush from another motor (held in the jaws of the red test lead) is a rather rubbish 100RPM, so it needs work. Probably uses a bunch of amps at that low rate too.
A comical aside - the motor was made by Johnson, not Howard Johnson though !
 
*Update* - Soldered 2 of the windings to the shaft, added a neo on top of the other, swapped the Li-Ion to a small 12V SLA.
The motor spun up to a very satisfying 2,000RPM. The initial rattle lessened off (pencil graphite scrubbed on the bare copper seatings helped) and I watched it for about 10 seconds. Then, oops, the approx 18 gauge windings were letting massive amperage through...one of my test leads started to melt !
Will semi-ditch this to await rewinding and swap to a regular DC motor.

[PhysicsProf]

  OK -- that's progress, Mark.  Thanks for working on this.

 I should say above, I see a correction may be needed -- not just a diode (leaky?), but a switch.  The idea is to allow the cap to charge (if it will do so!) while the generator is spinning, then switch OFF so the charge is maintained when the rotor is slowed and stopped.  


I'm thinking of a timed-switch, to switch the cap OFF after say 30 seconds, when the disc is spun for 60 seconds.  Also, it would be interesting to wait until the disc is up to a constant rotational speed before SWITCH ON -- to avoid acceleration effects.  (Also, try switch-on ONLY during speed-up...  or deceleration.  Interesting experiments.)  This may be overkill...  a simple diode should suffice for the first experiments.

[Slider2732]

Have put an ad out on our local Freecycle just now, for 'Any old Microwave'.
The thinking being to take the magnets out. After a good search, I have no large disk type magnets of any type. So that's compounded the bar magnet problem, but would yield a salvage source that will work
Hopefully that will produce results today...can't imagine many people around here hoard microwaves for energy experiments. Goat feed perhaps.

You'll have thought more on the diode/cap than I have Steve, but i'm not seeing how the cap would be shorted out. The diode will rectify coming in and then prevent drain on stop...wouldn't it ?
A manually timed switch on a spinning device might be a problem, unless there is a method or device in mind. I'd think a simple germanium diode FWBR would certainly prevent anything shorting, plus result in less voltage drop. 4x 1N4148 would be tried first, being as they're a lot more common.

[PhysicsProf]

  I was worried about the diode "leaking" more than I like, but a simple expt would find out...  Far from home and my electronics bench!

Thanks, Mark.  I have an old microwave at home, also (sigh).  I picked it up for $5 at a thrift store.

Q:   Where is the ring magnet located?

[Slider2732]

Never taken one apart   but I believe they are large ceramics of about 1/4" thickness, sat on the magnetron (sp?). From a vid I once saw where a guy stripped one down, the magnetron sits on the top.

Found another cordless drill and took the motor out, did the Dremmel'ing of the shaft and it sits now on the other side of the slate piece.
It spins up to a very healthy ~3000RPM it seems, on a 3.7V Li-Ion and of course the torque is excellent.
I'm using one of the 'platinum' disks from the HDD that was taken apart. The disk itself isn't magnetic (oddly enough in a way) and that's the main thing.
It's taking longer than i'm sure you would like, apologies about that.

Depends how long you are there for, but, how's Freecycle up that way for a similar idea ?
"Wanted: Any microwave oven and a cordless drill"

*Update* - Hooray, someone called Litha Craft emailed saying they have an old microwave in their garage. Just awaiting their address for pickup now

[Slider2732]

Bit of a saga. They didn't get the first email. I emailed again at 8pm and got a reply at 10pm, saying I could pick up.
Very kindly, the guy went out to the garage in the dark and brought it out, I expected collection tomorrow

[Slider2732]

OK...i've now got a system that's nearly ready to rumble
Rumble is the operative word, it needs balancing yet.

Have included a couple of pics of the microwave teardown Steve, to hopefully assist you in what is where and what things look like.
The main news though, is that these 2 magnets, found inside the magnetron are really very cool indeed. They are approx 2" diameter, one is 1/4" thick, the other is slightly thinner.

If you see tamper proof screws on the back of the microwave, grab a Dremmel (or similiar spinny thing) with a thin sanding disc on the end. Cut a groove in the screw and then you can use a regular flatblade to remove it
There were 2 of those on this Sharp Carousel.
Once open, you may note that all components are on one side, the side with the buttons and clock. This one didn't work when plugged in and...I found out why, it had been roach infested  
Needless to say, i've junked the electronics board. Roach pee on component legs will lead to a failure and some horrid smells. Yep, been there.
The magnetron is the large silver unit, it has vanes within.
The haul from this includes - transformer with 2kV output, AC 120V motor with fan, AC 120V motor that runs at 3RPM (lol), a 120V 20W lightbulb and socket, fuse and holder, some microswitches, a couple of sensors that I don't know what they are yet, a mains cord with spade endings  and a 1uF 2300V HV cap.
Also, not forgetting, that now it is a bare chassis, the rest makes a great and well known Faraday cage !

The style of the built up motor is 'Industrial Redneck'. That's not a mini V8 behind, it's a Pentium III heatsink.
The shaft is mounted on 2 roller bearings from 12V PC fans and allows smooth rotation. The shaft was extended by using a piece from a CD-Rom drive mechanism (that the laser assembly moves forward and backward on) and then linking with a piece of thick wire sleeve.
Vibratory wobble is caused by having to confabulate a way to change the motor shaft to the diameter of the magnets and HDD platter.
But...it's now lined up for cap and diode tests

 

[PhysicsProf]

OK...i've now got a system that's nearly ready to rumble
Rumble is the operative word, it needs balancing yet.

Have included a couple of pics of the microwave teardown Steve, to hopefully assist you in what is where and what things look like.
The main news though, is that these 2 magnets, found inside the magnetron are really very cool indeed. They are approx 2" diameter, one is 1/4" thick, the other is slightly thinner.

If you see tamper proof screws on the back of the microwave, grab a Dremmel (or similiar spinny thing) with a thin sanding disc on the end. Cut a groove in the screw and then you can use a regular flatblade to remove it
There were 2 of those on this Sharp Carousel.
Once open, you may note that all components are on one side, the side with the buttons and clock. This one didn't work when plugged in and...I found out why, it had been roach infested  
Needless to say, i've junked the electronics board. Roach pee on component legs will lead to a failure and some horrid smells. Yep, been there.
The magnetron is the large silver unit, it has vanes within.
The haul from this includes - transformer with 2kV output, AC 120V motor with fan, AC 120V motor that runs at 3RPM (lol), a 120V 20W lightbulb and socket, fuse and holder, some microswitches, a couple of sensors that I don't know what they are yet, a mains cord with spade endings  and a 1uF 2300V HV cap.
Also, not forgetting, that now it is a bare chassis, the rest makes a great and well known Faraday cage !

The style of the built up motor is 'Industrial Redneck'. That's not a mini V8 behind, it's a Pentium III heatsink.
The shaft is mounted on 2 roller bearings from 12V PC fans and allows smooth rotation. The shaft was extended by using a piece from a CD-Rom drive mechanism (that the laser assembly moves forward and backward on) and then linking with a piece of thick wire sleeve.
Vibratory wobble is caused by having to confabulate a way to change the motor shaft to the diameter of the magnets and HDD platter.
But...it's now lined up for cap and diode tests

 

Thanks for all these pointers and notes, Mark!  very helpful indeed.    My dremel etc. are back home, so I'm very much looking forward to your continued work on this...  especially the cap and diode tests!!

[PhysicsProf]

  Here's a vid on the homo-polar motor, says the torques are not = and opposite; apparent violation of Newton's third law (for torques):

http://www.youtube.com/watch?v=OZNWXmjPEwI

 And a nice experiment with two ring magnets --  surprised me somewhat:

http://www.youtube.com/watch?v=IlUY3snoWI8

And this comment on the above (hasn't been tried yet evidently no response from the vid-maker):

Can you please do thi;

Replace the rotating magnet on the dril by a conducting disk that is shorted out from center to perimeter to form a closed circuit. Put a small bulb in this circuit to confirm there's current flow when rotating the drill above the magnet This is basically faraday's homopolar generator. But the thing I want to get at is showing what happens to the bottom magnet that can rotate freely. It should spin in the other direction. According to newton's third law.

Please try it.

broli123

Hmmm...  Newton's third law violations...?  sounds familiar...