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The following device is apparently based on magnetic forces only and has no visible energy source:

enter image description here

Where is it's energy source?

Full video: http://www.youtube.com/watch?v=eA0b-8pqUCk

UPDATE

One of suggestions was that energy coming from heavy rod above the setup, which is lifted initially. Unfortunately, this gives us no more than

$mg dh$

of energy, which means that the energy of rotating wheel is no more than that value. Hence, on the next cycle, it will not be able to lift the rod again to the same level, especially regarding of friction, occurring in the rod-lifting mechanism.

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    $\begingroup$ I am not even going to watch the video (which is an income source for the scammer), but the tricks to make these things move are centuries old and with modern magnetics, batteries and materials they work just as nicely as they did in the 18th century, especially on poorly shot videos that leave a lot to the imagination. Give me and my hacksaw five minutes and we will have the "mystery" solved. $\endgroup$ – CuriousOne Jun 18 '15 at 8:23
  • $\begingroup$ Possible duplicates: physics.stackexchange.com/q/2167/2451 and links therein. $\endgroup$ – Qmechanic Jun 18 '15 at 9:03
  • $\begingroup$ @CuriousOne so you think this is the trick, i.e. there is some hidden energy source? $\endgroup$ – Dims Jun 18 '15 at 10:45
  • $\begingroup$ It's not a trick but a scam. Magicians do tricks to entertain you, the guy takes money from naive people who don't know better. :-) $\endgroup$ – CuriousOne Jun 18 '15 at 17:42
  • $\begingroup$ @CuriousOne don't consider jurisprudence, the question is physical $\endgroup$ – Dims Jun 18 '15 at 20:34
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When the system starts working, the round end of the iron slice on the side is on the top. This pre-stored gravitational potential energy and kind of "magnetic potential energy" is used to drive the system. The only thing one need to consider is how one can fight with friction and air-resistance so that this rotation can be sustained longer. In this case, when it is rotating, some energy are stored back into the magnetic field so that friction only takes a bit of energy away every revolution. After sufficiently long time, however, I believe it will stop.

In conclusion, this is a delicate device to fight with friction but it is not perpetual.

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  • $\begingroup$ Doesn't this energy return back once per cycle? $\endgroup$ – Dims Jun 18 '15 at 10:44
  • $\begingroup$ @Dims Yes. Not all energy can return since the friction must be non-zero. $\endgroup$ – Zheng Liu Jun 18 '15 at 10:52
  • $\begingroup$ Okay, may be you are right. Anyway, I didn't think about initial energy from lifted weight. Simultaneously, it seems to me, that it is not sufficient source... $\endgroup$ – Dims Jun 18 '15 at 11:02
  • $\begingroup$ @Dims I believe the initial energy comes from two parts. The most conspicuous part is the gravitational potential of the blunt end of the iron plate which is released when it drops down. However, this part is indeed not sufficient if you recall that a pendulum released exactly from the top can never complete a circle. The second part, energy stored in the magnetic field thus is important. This part can be perceived from the video when the system was driven by a magnetic bar held in the author's hand. $\endgroup$ – Zheng Liu Jun 20 '15 at 4:55
  • $\begingroup$ In the last part of the video, the device makes numerous number of cycles and shows no any (apparent) slow down, although friction in the lifting mechanism should be big. I can't imagine both of you sources provide enough energy. $\endgroup$ – Dims Jun 20 '15 at 9:58
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It's friction. The white rotating element is eventually going to stop rotating, so is the one with the magnetic spokes. There's also energy loss due to the white thing hitting the bar on the top because of sound, added to eventual loss of energy due to air resistance.

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There is energy stored in magnets by aligning magnetic moment of the individual clusters of metal so that all atoms contribute to a magnetic field in one direction. When you expose a magnet to an opposite magnetic force, you will deviate some of those clusters. De-magnetisation of magnets do happen, although at a very slow pace, but because it leads to alignment to be broken and all clusters having random alignments opposing against each other, it is truly a form of increasing entropy.

So yes, the magnetic wheel works and has enough strength to work against friction, and even drive some dynamo, possibly charging a smartphone or so. But if you were to create magnets from plain metal, you'd have to provide much more energy to produce a magnetic field strong enough to align all the clusters again.

So no, this is not quite "perpetual motion" as conceptualized by ancient Greeks, much like coupling a nuclear reactor with an electric motor is not perpetual motion.

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  • $\begingroup$ If we were to trust the author of "selected work of T.S. Spivet", the magnets will lose their properties after about 400 years. $\endgroup$ – PypeBros Jan 9 '16 at 13:14

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