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There are many videos on youtube in which people arranged magnets in circle and rotated one placing in middle of that circle on a shaft, and the magnet (magnet motor) starts madly and continues its movement.
Do they really rotate infinitely?
If so, do they from where they get that extra energy to move so fast and infinitely?

EDIT: This question is about real world scenario

UPDATE: I am unable to find that particular video about which i talked about -- I added them to my favourites, but they are all now deleted :( -- there are hundreds of that that kind of videos. Some example videos links
http://www.youtube.com/watch?v=dT9s33X9D4I
http://www.youtube.com/watch?v=yei0NMqUaZ8
http://www.youtube.com/watch?v=5DvPLFX5gwA
http://www.youtube.com/watch?v=i0oUaPZ_wF8
http://peswiki.com/index.php/OS:Screw-Magnet_Motor
http://www.youtube.com/watch?v=aHVBu77jz4w

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This whole question is pseudo-science and woo. I'm voting to close. –  Colin K Feb 1 '11 at 18:07
    
With the proper rewording, this question would fit on Skeptics. Please do not migrate, but the OP may want to open it there. –  Ebenezer Sklivvze Dec 27 '12 at 21:52
    
@Sklivvz While posting I thought that physics experts would be able to answer it better than skeptics. That is why I posted it here. I am going to post it on Skeptics as well. –  LifeH2O Dec 28 '12 at 4:40
    
this is the skeptic question. If I may, I think you should close this question and eventually answer on skeptics. skeptics.stackexchange.com/q/14283 –  Duralumin Dec 28 '12 at 8:14

3 Answers 3

Anything can rotate infinitely, if there is no friction. Rotating an object with constant velocity uses no energy to maintain. With friction it will loose energy and eventually stop. If you add a static magnetic field to the object, it will gain some finite potential energy, which in turn can be converted to kinetic energy.

Now if you add a changing magnetic field, you can make it continuously rotate or even accelerate, but this requires energy to maintain. This is how regular electromotors work, the battery is an electromagnetic potential, and will give the motor kinetic energy, but eventually the battery will be depleted.

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I am asking about real world scenario –  LifeH2O Dec 24 '10 at 13:14
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Physics applies to the real world. –  user1708 Dec 24 '10 at 13:21
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Everithing is rotating infinitely. The process is unstopable. Pick any galaxy, any planet, any star. It is rotating. In relation to what? They rotate –  Helder Velez Feb 25 '11 at 0:15
    
In real world scenario there is friction and other energy losses involved. To overcome them some extra energy is needed. Which apparently means magnets can be exploited to produce energy. –  LifeH2O Dec 28 '12 at 4:38
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What I have asked is about permanent magnets, as shown in videos they are moving continuosly hence overcoming energy losses which means these system are actually producing some energy. Are all of these systems fake (see the last video youtube.com/watch?v=aHVBu77jz4w) –  LifeH2O Dec 28 '12 at 6:21

Looking at the first video -- if magnetism was sharply directional (i.e. a little searchlight of attraction coming out from the tip of the magnet) then this device would work. Unfortunately magnetism is (roughly) an omni-directional field and so doesn't just let go of one screw and start tugging on the next. The field attracts strongest the objects that are closer and attracts more weakly the objects that are farther away. If you make the magnet strong enough to start pulling at the screw-head that is next in line it will be strong enough to pull very strongly at the screw-head that is passing under it.

The person who built this wants a force to be applied to the drum at a tangent to the surface of the drum (kind of like a rope wrapped around it) to spin the drum. But any force applied by the magnet is going to be nearly straight out, which won't induce a tendency to spin.

The proof comes from the fact that the device doesn't self-start. When the magnets are brought close to the drum the drum jiggles a bit as it comes to a static resting place, but the supposed spinning force doesn't happen -- the narrator has to start it spinning.

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""if magnetism was sharply directional (i.e. a little searchlight of attraction coming out from the tip of the magnet) then this device would work."" This is nonsense! Ever heard of first law of thermodynamics? -1 –  Georg Feb 1 '11 at 16:32
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I was trying to discuss why the device doesn't work by considering what changes to physics would be required to get it to work and then explaining what happens in the real world. At no point do I suggest that there is a way to get the device to work. –  David Rouse Feb 2 '11 at 13:15
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@Georg it's not nonsense. The point is that if magnets were like searchlights, then it would break the first law. But they're not, so it doesn't. –  Nathaniel Dec 19 '12 at 13:39

Not without some sort of external power source. Extremely low power neodymium magnet pulse motors are a reality though, and can be powered from the ambient energy in the environment.

EDIT: has to be said though, that extremely low power magnet motors are more like electromechanical oscillators than motors.

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"can be powered from the ambient energy in the environment" Absolutely not. This is free energy/perpetual potion nonsense. –  Colin K Feb 1 '11 at 17:02
    
youtube.com/watch?v=3PEjvPxrmEo –  Janne808 Feb 1 '11 at 17:08
    
youtube.com/watch?v=OMVtGxSYdhU –  Janne808 Feb 1 '11 at 17:13
    
""can be powered from the ambient energy in the environment" Absolutely not. This is free energy/perpetual potion nonsense. – Colin K 17 mins ago" QFT –  Janne808 Feb 1 '11 at 17:22
    
I cannot vouch for low power neodymium magnet pulse motors but the widely known en.wikipedia.org/wiki/Drinking_bird uses ambient energy to power itself and is not regarded as "free energy/perpetual potion nonsense". –  João Portela Apr 18 '11 at 16:55

protected by Qmechanic Dec 19 '12 at 12:46

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