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Author Topic: Homopolar generator with co-rotating magnet  (Read 2889 times)

Offline LeoFreeman

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Homopolar generator with co-rotating magnet
« on: July 03, 2021, 01:11:11 PM »
I was hoping someone could possibly point out why this arrangement would not not generate a current to light the bulb?
The whole circuit is monolithic, with no brushes or articulating parts. The entire device would be rotating in free space.

The copper disk is gripped around the edge between the poles of numerous closely-spaced horseshoe magnets.
Their magnetic fields only cut across the copper disk in a narrow band close to the rim, where the velocity is greatest. Electrons in that band would be forced radially to the very edge of the disk and into the "spokes" that run from the rim to the wheel axle.
The spokes pass through the gaps between the ring magnets where the magnetic fields should be very weak, and thus not cause any back-resistance to the electrons trying to leave the disk.
The current would then flow out along the conducting sheath to the light-bulb, and return to the disk via the axle..


Offline Cadman

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Re: Homopolar generator with co-rotating magnet
« Reply #1 on: July 03, 2021, 02:25:19 PM »
You have ~72 individual magnets, each with their own magnetic field. The magnets and their fields rotate with the disk so there is no relative movement between the disk and magnetic fields, so no induction and no current.
The field would be stationary I think if there were a one piece magnetic torus with a single north and south pole at a slit for the disk. That would be an interesting experiment.

Offline LeoFreeman

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Re: Homopolar generator with co-rotating magnet
« Reply #2 on: July 03, 2021, 02:51:03 PM »
I thought that the "Faraday Paradox" dealt with exactly that case, where a current is generated even though the magnet turns with the disk? Sorry if I misinterpreted your remark.
BTW, you,re spot on with your magnet count!

Offline Cadman

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Re: Homopolar generator with co-rotating magnet
« Reply #3 on: July 03, 2021, 03:04:37 PM »
Your question now makes me think the torus field would also move with the torus.

Correct me if I'm wrong but I think the magnetic field is only stationary when the magnet is rotated on it's own NS axis.

Your idea has every magnet orbiting the disk axis and each magnet carries it's field along with it in the same orbit.

Offline LeoFreeman

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Re: Homopolar generator with co-rotating magnet
« Reply #4 on: July 03, 2021, 03:36:23 PM »
I'm not sure, but I thought that, topologically, all these horseshoe magnets just form one large ring magnet,
corresponding to a normal pair of large disk magnets, just with a big hole drilled down the middle.   

The middle section of the disk is not moving very fast, so that part doesn't need a strong field, but I could be mistaken. 

Offline Cadman

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Re: Homopolar generator with co-rotating magnet
« Reply #5 on: July 03, 2021, 03:59:08 PM »
Each magnet's field would be concentrated in the gap between that magnet's N & S pole. Since those gaps orbit with each magnet, so would the field.

Offline LeoFreeman

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Re: Homopolar generator with co-rotating magnet
« Reply #6 on: July 04, 2021, 01:13:50 AM »
Ideally, the poles of the magnets should form a continuous ring. The Faraday wheel works even if the magnet co-rotates with the disk,
so that part should be the same.

 The main big difference in this device, however, is in the way the magnetic field is confined to the horseshoe magnets,
as compared to Faraday wheels that simply use open-ended magnets, where the stray field can cause back-emf in the current conductors if they move through it
 
The big question is: Can an electric current in a wire pass unaffected through a region of magnetic field, 
IF the field is confined to a high-permeability material,
AND the wire passes through a gap in the material, so that the flux lines are ducted around the wire?      .

Offline LeoFreeman

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Re: Homopolar generator with co-rotating magnet
« Reply #7 on: July 07, 2021, 01:31:12 AM »
Here is another version that may achieve a higher output voltage, by having many loops
of wire in a sinusoidal pattern. (only one full loop is shown here, but the sinusoidal pattern
would be repeated many times around the disk.
The applied magnetic field changes direction on each Inward and Outward going section of the wire,
so the electrons are pushed in the same direction, until the wire exits towards the light-bulb at
the centre.