N-machine theory tested

[PaulLowrance]

Hi,

Long ago when the late Bruce DePalma lived in Santa Barbara, CA, I've visited Bruce numerous times. His N-machines are very impressive looking. Bruce said the reason the N-machine worked was because the magnet was bonded to the disc, and therefore if DC current flows through the disc, there are two opposing rotational forces, one on the disc, and the opposite on the magnet. So if you rotate the N-machine, place a load on the disc, thus producing current, there should be no net opposing angular force on the N-machine.

That's fine, but I just tested that theory. I shorted a 30+ amp DC supply across a NdFeB disc magnet, and it rotated! My magnet is not on an axis, as it was on the carpet, but it still rotated in place.

Maybe someone who has a strong magnet on an axis could verify this as well.

Paul

[jadaro2600]

I would like the results to this test as well.

I hear numerous things about the unusual fields formed by the magnets.. something about their field strength near the periphery vs that of the inside.

[broli]

Hi,

Long ago when the late Bruce DePalma lived in Santa Barbara, CA, I've visited Bruce numerous times. His N-machines are very impressive looking. Bruce said the reason the N-machine worked was because the magnet was bonded to the disc, and therefore if DC current flows through the disc, there are two opposing rotational forces, one on the disc, and the opposite on the magnet. So if you rotate the N-machine, place a load on the disc, thus producing current, there should be no net opposing angular force on the N-machine.

That's fine, but I just tested that theory. I shorted a 30+ amp DC supply across a NdFeB disc magnet, and it rotated! My magnet is not on an axis, as it was on the carpet, but it still rotated in place.

Maybe someone who has a strong magnet on an axis could verify this as well.

Paul

This is homopolar 101. The reason why it rotates is because both the disc (the coat of your neodymium mag) and the outside circuit (what you are brushing it against) want to torque the magnet. But since the magnet is attached to the coating this torque will vanish and all that remains is the torque due to the outside circuit, this will cause rotation. Unfortunately while rotating the coat will start generating back emf due to its motion and the presence of the magnetic field.

The interesting part which I have seen one person experiment with so far is that you can manipulate the flux of a magnet. Magnetic flux confined due to a ferromagnetic material is a very strange phenomena. You can guide it and only concentrate it on a portion of a circuit and use classic laws like the Lorentz force law to deduce force. Below you see an old concept of mine that does this. This concept though doesn't solve the back emf problem, but we know that any force has a reaction force, which in this case acts on the magnetic setup. This can cause it to rotate, so one can leave the circuit stationary and allow the setup to rotate without any bemfs where the only speed limit is component dependent.

[PaulLowrance]

I hear you broli. I'm only saying that this experiment goes against what Bruce told me. All these years I never even thought to question him. 

It would be great if someone could do this without the magnet rotating, but just make sure the friction is low enough.

[PaulLowrance]

This photo was grabbed online, but it looks just like my magnet. So I placed two thin stiff wires on the magnet, one on the outer edge, and one on the center of the disc. It seemed to work best on carpet. Perhaps less friction.