What's different about a uniform magnetic field?

[lumen]

Hi Vineet


You are correct about the ring magnet not showing any force against the copper disk.
What I was trying to find out is whether the charge separation is the same when entering the track as it is in the uniform center area.


The results show that the charge separation is the same entering the track as it is in the center uniform field. It only needs a path to allow the electrons to flow back to the depleted side of the separation.
That means that the copper disk having no drag in the uniform field would have drag if there was a path for the charge separation to equalize.(the brushes on a homopolar generator make this path)
It also shows that it's not so much the current flowing around the conductor that produces the drag but more the fact that the current is continuously flowing and doing work that causes drag.
The current flow itself hinders the advancing magnetic field.


By examining all the details carefully, many answers are shown in these two simple tests.


The clue for a multi turn DC homopolar motor is in the scope shot that shows one side of the coil moving in a uniform field and the other side of the same coil moving in the segmented side.
Suppose the segmented side rotated with the coil and the windings cut through the low field notches between the segments. This would leave a path for electron flow within the uniform field side of the coil.
I was thinking that should be the next test.

[lumen]

What I found different in a uniform field is that there is no difference!
When moving into a uniform field there is drag because there is still a conduction path.
Once in the uniform field the conduction path is missing so there is no drag.
If a conduction path is provided while moving in a uniform field then there is again drag.

The final proof that a uniform magnetic field causes the same current flow and lenz drag as expected.

https://youtu.be/nlppD5Lteec

[shylo]

Hi Lumen
Thanks for the test's, what is the pole oreintation, all norths facing souths
or nsn facing sns you did say they were in attraction right?
artv

[lumen]

Hi Shylo

All the poles are N along one side and S along the other so the flux flows in a circular path through the "C" channel and across the gap.
This makes the field very tight across the gap with almost not field outside the setup.
It becomes very clear what is going on in the uniform part of the field and in fact this setup causes all the field to be uniform right to the ends.

I'm now making some changes to the rotary device so that it will rotate only one ring magnet to see if there is a way to build a conduction path (without brushes) that will cause drag on the single rotating ring magnet. This is thought to be impossible and likely is, but if the flux is controlled in a tight loop it may be possible to have areas free of flux on the other side of the loop. This was seen in the copper disk setup.