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Help with permanent magnets configuration as a movement source.

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Jul11-14, 11:48 AM
P: 10
Accidentally I have noticed a strange behaviour using two different magnets, which I would like to discuss.
The picture shows a disc magnet (shown also in the right to see the magnetization) with it's N facing upwards.
Onto the disc magnet N side, a cylinder magnet is placed. When the cylinder magnet is placed, as shown in the picture, an attraction force happens to it's S (as the arrow shows), because it is attracted by the disc magnet N. The cylinder magnet N is repelled as the arrow shows.
All the above are the facts as noticed by experimentation.

Now the question.
If I force the cylinder magnet to this place shown and I do not alow it to move in any direction other than right or left, the magnet tends to slip from my hand and follow the direction of the red arrow.
I think I can explain this fact, what I cannot explain is the next one:

What if I continuously force the cylinder magnet to be in that angular position in respect to the center hole of the disc magnet? Will the cylinder try to move forwards indefinitely, and as a result spin around the center hole? Well, of course not! but why this would not work?

I appreciate your explanations
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Jul11-14, 01:01 PM
blainiac's Avatar
P: 28
I remember when I was younger working with magnets and trying to get the correct configuration, every time it would never work, no matter how clever I thought I was. The magnets 'knew' and always stopped moving or getting to a sticky point.

With this configuration (if I'm looking at it right), try to imagine the set up where the cylinder magnet can spin around the axis (where the hole is). Let's say we spin it around its axis and take a picture of it at every 36 degrees (10 pictures for a full rotation). You will see it will stop after a bit if spun (from the initial energy you put into rotating it). The reason is, nothing is really changing in this set up.

If you look at the pictures of it spinning and line them up where the cylinder magnet is in the same position in each, you will notice the magnet that is spinning never really does anything. The cylinder magnet never increases its distance from the hole, and doesn't feel a net change if constricted to an axis.

If the magnet is free to 'choose' where to go and not restricted to an axis, the cylinder magnet will reach a point where it will move and settle in a place. If you try to remove it from that place, it will require more energy, as it's at the bottom of the 'magnetic' well.

I hope I see your description correctly, I'll try to draw a picture soon.
Jul11-14, 01:14 PM
P: 10
Thanks a lot for your explanation,
That was what I initially thought, that nothing really changes there, two permanent magnets can never yeld to a rotation.
Thanks once again

Jul11-14, 01:49 PM
blainiac's Avatar
P: 28
Help with permanent magnets configuration as a movement source.

No problem! There are some interesting ideas floating around on the web, but as magnetic fields are conservative (like gravity), you can never get more out than in. Keep thinking about them, as this really helps in visualizing and thinking about unrelated things in life.
Jul11-14, 02:56 PM
P: 10
It will be the ultimate challenge to achieve constant movement from stationary magnets and maybe some help components.
I have a feeling that the answer lies in "instantly rerouting" the magnetic field of permanent magnets.
In fact I have seen an experimental linear motor on the web doing so but I cannot find it now.
Thanks for not discouraging new experimenters to experiment even with crazy ideas like this. Even if nothing comes out, we all learn from the mistakes and sometimes the mistakes lead to new ideas :)
Jul12-14, 02:38 AM
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What picture?

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