I would guess that it all depends on how strong your magnet is, and how close your magnet is to the copper. I would be interested to see what kind of current flow you will actually see between any two points. My first guess would say that there is too much symmetry and restricted current paths and high conductivity to see significant eddy current heating or any net current flow.

If any current can be induced to flow, completing the circuit in your coil will likely slow the spinning magnet. I assume from the image in your first post, that the two leads on the coil are not connected as the initial state.

What software will you use to simulate this?

I have no software to simulate this... that's why I'm going to build it... My guess is still that it will still heat up, but I doubt it will be only because of eddy currents. I'm going to make to versions of the toroid, one wide enough on its outer diameter so that the magnetic lines cut only through its inside, and one with both diameters close together. Then I'll test them open and short circuited, and with a resistive load at its ends... see what happens.
And thanks for the warning... I didn't realize that those words here were as bad as saying the "B" word on a plane... I won't use them again

 

The mere mention of perpetual motion won't close a thread. Only advocating such a thing or trying to get help from members here is verboten as a time waster.

One way to simplify your coil would be to simply replace it with a section of pipe large enough to contain the spinning magnet. You'll note a substantial drag on the spinning magnet, a force on the pipe making it want to rotate with the magnet even if the pipe is not ferrous, and eventually you'll see warming of the pipe.

Your coil will simulate the section of pipe, but less effectively. Some field lines will leak out and it will be harder to see any heating because the coil will dissipate it to the air. The rotational force will want to rotate or distort your coil, so be prepared for that.

You should watch this video. There are many similar ones but I like this one.

 

The mere mention of perpetual motion won't close a thread. Only advocating such a thing or trying to get help from members here is verboten as a time waster.

One way to simplify your coil would be to simply replace it with a section of pipe large enough to contain the spinning magnet. You'll note a substantial drag on the spinning magnet, a force on the pipe making it want to rotate with the magnet even if the pipe is not ferrous, and eventually you'll see warming of the pipe.

Your coil will simulate the section of pipe, but less effectively. Some field lines will leak out and it will be harder to see any heating because the coil will dissipate it to the air. The rotational force will want to rotate or distort your coil, so be prepared for that.

You should watch this video. There are many similar ones but I like this one.

I would agree that a copper pipe section will have a significant drag but he doesn't have that. He has a wire mesh - which makes it interesting. A toroidal slug of iron behaves much differently than a toroid made of iron powder with insulative oxide layer ofer each particle of iron power. I look forward to the experimental results.

 

The mere mention of perpetual motion won't close a thread. Only advocating such a thing or trying to get help from members here is verboten as a time waster.

Thanks for clarifying, I had thought that in this forum the subject was taboo, blasphemous and akin to incest or worse...

You should watch this video. There are many similar ones but I like this one.

That is a very impressive video... it's amazing to see how the eddy currents generate magnetic fields of the opposite sign that affect both the magnet and the pipe... bet both pieces are quite pricey too... thanks.

 

I would agree that a copper pipe section will have a significant drag but he doesn't have that. He has a wire mesh - which makes it interesting. A toroidal slug of iron behaves much differently than a toroid made of iron powder with insulative oxide layer ofer each particle of iron power. I look forward to the experimental results.

So do I... of course I expect eddy currents to manifest in one way or the other, but that's not the only thing I'm expecting

 

So do I... of course I expect eddy currents to manifest in one way or the other, but that's not the only thing I'm expecting

What else are you expecting? Perpetual energy? ... Oops!

 

What else are you expecting? Perpetual energy? ... Oops!

you will incur in the god's wrath if you keep this up... they'll release the kraken on ya... or worse...

 

the diametric poles on your rotor beg for a path to the opposite side of your stator coil. a couple of thin wooden discs, on either side of your rotor. make them just a tiny bit larger than the magnet. then wrap your coil around the outside of the discs crossing over down the other side at 180 deg. point. then just keep wrapping and progress clockwise around the discs, making the wire deviate around the axle in a repeating pattern all the around.
putting a solid ring of hardened steel around this to increase the flux density would maximize the current in the coil and also provide additional heat from eddy currents in the solid mass of metal. and if heat is important, make your coil out of soft steel wire instead of copper

 

Hi,

It looks like you can reduce this problem to just two turns that are being energized and two that are not, and they are all connected in series.
The two energized turns produce local currents, the two non energized turns are just resistances.
The two energized produce temporary local currents. These currents do not flow through the resistances because they are opposite.
The magnets then leave the vicinity of the energized turns, then enter the vicinity of the non energized turns so the roles of the two sets of turns are reversed.
Later the same thing happens so the roles are reversed back to the initial state.
So it seems that current can not flow through the entire wire, but electrons will move back and forth locally which would cause heating in that region, and also set up two AC voltages across the coil in two different places, but those AC voltages will rotate with the magnets as they turn.

The above scenario would be for the steady state solution. To find out what happens during start up we would have to consider that the North pole energizes its initial region before the South pole gets there, and vice versa, which means a temporary DC voltage would be set up also in two different regions during start up.

 

Hi,

It looks like you can reduce this problem to just two turns that are being energized and two that are not, and they are all connected in series.
The two energized turns produce local currents, the two non energized turns are just resistances.
The two energized produce temporary local currents. These currents do not flow through the resistances because they are opposite.
The magnets then leave the vicinity of the energized turns, then enter the vicinity of the non energized turns so the roles of the two sets of turns are reversed.
Later the same thing happens so the roles are reversed back to the initial state.
So it seems that current can not flow through the entire wire, but electrons will move back and forth locally which would cause heating in that region, and also set up two AC voltages across the coil in two different places, but those AC voltages will rotate with the magnets as they turn.

The above scenario would be for the steady state solution. To find out what happens during start up we would have to consider that the North pole energizes its initial region before the South pole gets there, and vice versa, which means a temporary DC voltage would be set up also in two different regions during start up.

Thank you very much for your detailed explanation. I've been thinking along the same lines all this time too, I expect there will be some sort of colliding AC waves along the toroid. My intention is to short circuit the thing, not to just let it remain open. So whatever happens, it will be a cyclic event that I intend to study with my oscilloscope. As I stated before, I expect heat to manifest itself and not just because of eddy currents... I expect that maybe a lot more heat will be produced.
Now for the big idea: if (and only if) my first experiment more or less works the way I expect it to (that is, producing much more heat than if I were to run the magnet inside a thick-walled copper tube), then I intend to build a much bigger toroid (say about 6" ID) but this time using copper tubing instead of wire, and then run water through it, see how much it heats up and at what rate...

 

Thank you very much for your detailed explanation. I've been thinking along the same lines all this time too, I expect there will be some sort of colliding AC waves along the toroid. My intention is to short circuit the thing, not to just let it remain open. So whatever happens, it will be a cyclic event that I intend to study with my oscilloscope. As I stated before, I expect heat to manifest itself and not just because of eddy currents... I expect that maybe a lot more heat will be produced.
Now for the big idea: if (and only if) my first experiment more or less works the way I expect it to (that is, producing much more heat than if I were to run the magnet inside a thick-walled copper tube), then I intend to build a much bigger toroid (say about 6" ID) but this time using copper tubing instead of wire, and then run water through it, see how much it heats up and at what rate...

The wire cannot heat up more than the power put into turning the magnet. That is, if heat is generated anywhere, then the heat is created by the mechanical force of turning the magnet's field through a conductor. Therefore, any 'response' you may get between wire and magnet will require the magnet to be turned with greater energy to maintain the same speed as without the wire cage being present.

So, to answer your question, the temperature and rate will be a function of, input power to the magnet and energy transfer to the wire cage (made of copper tubing filled with water in your final question). I doubt it will be much with a small flat permanent magnet.

 

The wire cannot heat up more than the power put into turning the magnet. That is, if heat is generated anywhere, then the heat is created by the mechanical force of turning the magnet's field through a conductor. Therefore, any 'response' you may get between wire and magnet will require the magnet to be turned with greater energy to maintain the same speed as without the wire cage being present.

So, to answer your question, the temperature and rate will be a function of, input power to the magnet and energy transfer to the wire cage (made of copper tubing filled with water in your final question). I doubt it will be much with a small flat permanent magnet.

Yes I understand what you're saying... I do expect the magnet's rotation to meet with higher resistance because of the electric reactions (eddy currents and otherwise) taking place in the toroid... the bottom line of what I'm trying to find out is this: Assuming the same RPMs for the test (reaction torque, of course, may vary), Will more, less, or an equal amount of heat be generated in the toroidal coil arrangement than if I were to use an ordinary copper tube with solid walls instead?

 

Yes I understand what you're saying... I do expect the magnet's rotation to meet with higher resistance because of the electric reactions (eddy currents and otherwise) taking place in the toroid... the bottom line of what I'm trying to find out is this: Assuming the same RPMs for the test (reaction torque, of course, may vary), Will more, less, or an equal amount of heat be generated in the toroidal coil arrangement than if I were to use an ordinary copper tube with solid walls instead?

Ok. I put my guess in an envelope and sealed it shut. Yup, it will be opened and read when the experiment is complete. I just sat down and wrote, L-E-S-S on a piece of paper and put it in the envelope and set it aside. I will take it out and read it when you are done with the experiment.

 

Ok. I put my guess in an envelope and sealed it shut. Yup, it will be opened and read when the experiment is complete. I just sat down and wrote, L-E-S-S on a piece of paper and put it in the envelope and set it aside. I will take it out and read it when you are done with the experiment.

yeah... and afterwards you can take another piece of paper and write ITOLDYOUSO and mail it to me as a gift to be framed and hung in my shop... maybe if your calligraphy is elegant enough I'll even sign it with a lessonlearned beneath it...

 

"I told you so" will be available soon.

 

"I told you so" will be available soon.

Thanks for the laugh... I needed it... I've been having a crappy day...

 

Your coil will simulate the section of pipe, but less effectively. Some field lines will leak out ...

That means L-E-S-S.

 

That means L-E-S-S.

Yet another unwavering supporter... anyway, I'm glad you've warned me... I'll wrap enough wire and at least two rounds of pipe to make sure that no lines leak out

 

While I doubt your experiment would deliver much other than a negative result I wish you luck.
There may be a small emf generated across the coil terminals due to any (virtually unavoidable) asymmetry in the construction.
Consider a normal ideal ac machine in which the stator winding is constructed on a laminated iron core. There's no reason one couldn't construct your model with such a laminated core - one simply has to get the lamination orientation correct as in any machine. Consider also that the rotational drag on a real unloaded machine (generator) is very low - primarily from windage & friction rather than eddy current.
The essential difference in your case is the layout of the windings - which is entirely different to that found in a real machine.
It seems to me you have few committed protagonists willing to back your assertion. Can't wait to hear how it goes.

 

Can't wait to hear how it goes.

Thank you, that's the spirit... I'm doing this out of sheer curiosity... there is no such thing as a failed experiment when one isn't 100% certain of the outcome, just a learning experience... though in my case it might be a little humiliating ... or not ...
BTW, I'm not going to put time into this thing until a few weeks for now ... and I'm thinking about skipping the small toroid part and go for the big one, if I can find a magnet of the proper size... hope you're a patient person