# Thread: Why Magnetic Perpetual Motion Won't Work?

1. I had been thinking about this idea for a perpetual motion machine using permanent magnets, when something dawned upon me. I think I've figured out why a magnetic perpetual motion machine wouldn't work, but I'm asking this to confirm with any knowledgeable people out there. My basic question is, if the permanent magnets are doing work (aka. using energy), would they wear out (ie: are they really permanent), or do permanent magnets really use energy at all?

My guess is that they would wear out. Lets take a classic permanent fridge magnet.

1. When the magnet is first going onto the fridge. Now lets just pretend that the fridge itself is not a permanent magnet, rather just a metal that the magnet will eventually stick to. You feel the pull of it from your fingers. You let go and the magnet flies (a small distance) to the fridge without any work from you. Energy, from somewhere, moved that magnet through the air to the fridge. Here I'm guessing that energy is coming from the magnet, and it did lose some energy.
Note: I may be wrong here in calling it "energy" when it may just be "potential energy" since I guess the magnet needs some attractable metal nearby to "activate" that potential. Think "distance from a mass" as to "gravitational potential energy".

2. When the magnet is stuck on the fridge. The magnet goes on the fridge. It sits there... time passes... you can't remember the last time you moved the magnet. It could have been 20 years, but that magnet is still there. Here I'm guessing that no energy was used at all. I'm thinking that the magnetic fields had some sort of "static friction" effect between the magnet and a fridge. This made it just like sticking a thumb-tac in drywall. So that friction kept the magnet there, but since the magnet didn't move, it didn't do any work and hence didn't use any energy.

3. If my general idea in case 2 is right, then there is another question. If the magnet essentially has to cause (or greatly increase) the friction between itself and the fridge in order for it to stay there, then how can physicists say that no work is being done by the magnet? Or does the magnet, by its magnetic nature, cause the friction and thus allows it to stay on the fridge. Why isn't energy being used here?

So in summary, I'm thinking the term "permanent magnet" does not in fact mean permanent. Rather, the magnet is permanently magnetized without the addition of external fields, while non-permanent magnets require external fields to truly become magnetized.

Are my ideas right here? Please elaborate, I'm in engineering school and should be able to understand most technical answers. Thanks for your time!

2.

3. Originally Posted by rxan
3. If my general idea in case 2 is right, then there is another question. If the magnet essentially has to cause (or greatly increase) the friction between itself and the fridge in order for it to stay there, then how can physicists say that no work is being done by the magnet? Or does the magnet, by its magnetic nature, cause the friction and thus allows it to stay on the fridge. Why isn't energy being used here?
Energy isn't being used because there is just a force without any motion. It is the same as if you are sitting still on the earth. There is a gravitational force holding you against the earth, just like the magnet is held to the fridge.
So in summary, I'm thinking the term "permanent magnet" does not in fact mean permanent.
No, it doesn't have anything to do with the magnet being permanent or not. Gravity is permanent and still you need motion to do work. Don't confuse force with energy.

4. I agree totally with harold on this one.

F due to gravity=mg if gravity doesn't pull some thing down then its a normal force or N=mg this normal force is perpendicular to the plane.

work is defined as Force x distance x cos(angle)

No distance traveled by the magnet it just stays on the fridge.

Energy = energy Kinetic + energy potential

The magnet wont fall because its the force that keeps it stuck to the fridge. so no potential

The magnet isn't falling so it also has no kinetic energy.

If you want to know more about whats really happening between the magnet and the fridge look at some stuff on ferromagnetism.

oh and your right that permanent magnets are not really permanent. they can randomly weaken over time or if you heat them to certain points they lose their magnetism. But When I say randomly weaken I don't mean all the way. Scientist know that the geomagnetic field has reversed so many times because they have found lava flow magnets that are extermely old. So I believe that this weakening process would be some where in the billions of years. without like I said heating a magnet.

5. So a permanent magnet which is attracting/repelling metals or other permanent magnets does or does not become demagnetized over time?

Lets assume that we aren't heating the magnets up a lot. And I understand that all permanent magnets would probably demagnetize over extremely long periods. But would the fact that the magnets are causing motion make them demagnetize at a far more drastic rate?

6. There was a long discussion about this on the Partsexpress forum regarding the deterioration of the magnet on a speaker driver (Yes, before coming to this forum, I spent 2 years heavily studying home theater sound) due to magnetic interaction with surrounding metals or magnets. We came to the conclusion that a magnet interacting with a metal, holding the same position over time, would have little to no effect on the magnet; but if you were to have multiple magnets sitting next to each other so that their fields could interact, it would in fact shorten the life span by altering the current of the field, and contorting it enough so that its sustainability goes down. But of course, that was just our conclusion.

7. Originally Posted by Cold Fusion
We came to the conclusion that a magnet interacting with a metal, holding the same position over time, with have little to no effect on the magnet; but if you were to have multiple magnets sitting next to each other so that their fields could interact, it would in fact shorten the life span by altering the current of the field, and contorting it enough so that its sustainability goes down. But of course, that was just our conclusion.
Hold on a minute, a single magnet can be considered as a number of magnets 'fused' together. Or on a grander scale as a number of magnetic domains, so what led you to the conclusion above ?

Have a look at the magnetic map of the Atlantic mid ocean ridge, these weak magnetic strata are aligned in various ways yet after all this time (many millions of years) they still create a magnetic field.

8. I'm still not getting any plain answer here about whether permanent magnets would demagnetize or not. Lets assume we have magnets 1 and 2 in the following configuration:

N [magnet 1] S <--distance 'd'--> N [magnet 2] S

Lets assume:
- When one magnet pushes the other, they stay perfectly aligned.
- Initially when one magnet is pushed against the other, the magnetic forces cause the magnets to stay apart a minimum of distance d.

Now if I continuously push magnet 1 to the right, towards magnet 2, the magnetic forces cause the magnets to stay apart a distance d. Both magnets will move to the right and stay apart a distance d.

Questions:
- Will either of the magnets ever demagnetize? In other words, would the distance between the magnets eventually decrease as the the magnets demagnetize?
- Is energy from the magnets being used here? Why not?

9. I'm tired so maybe I missed something, but based on what I read, your model is flawed.

N [magnet 1] S <--distance 'd'--> N [magnet 2] S
Unlike poles attract, so if you push magnet 1 towards magnet 2 as stated, they will eventually bond forming one magnet and your d will = 0.

Get your poles right and maybe the question will make more sense...

10. Haha. OK here's a re-draw.

N [magnet 1] S <--distance 'd'--> S [magnet 2] N

11. It doesn't matter whether the magnet's demagnetize over time or not, that's not the reason that you can't use permanent magnets to make a perpetual motion machine.

12. Ok. Energy is only used if something is physically moved toward the magnet. If that thing is every moved away again, the energy is given back.

Basically, you're taking and giving back again and again, but it's never a one way street. So, you can't make a perpetual motion device in the sense of one that creates free energy.

Originally Posted by Anonymous
Originally Posted by Cold Fusion
We came to the conclusion that a magnet interacting with a metal, holding the same position over time, with have little to no effect on the magnet; but if you were to have multiple magnets sitting next to each other so that their fields could interact, it would in fact shorten the life span by altering the current of the field, and contorting it enough so that its sustainability goes down. But of course, that was just our conclusion.
Hold on a minute, a single magnet can be considered as a number of magnets 'fused' together. Or on a grander scale as a number of magnetic domains, so what led you to the conclusion above ?

Have a look at the magnetic map of the Atlantic mid ocean ridge, these weak magnetic strata are aligned in various ways yet after all this time (many millions of years) they still create a magnetic field.
Read what he said more carefully. The deterioration comes from the magnets altering one anothers' magnetic fields. If all of their fields were in perfect sync, that problem would go away.

You're right that a single magnet can be considered multiple magnets, but they're multiple magnets that are all in sync.

13. Thanks for the explanations everyone!

kojax:
You say that energy is only used if something (ie: a metal piece) moves towards the magnet because of the magnetic fields. I guess what I'm trying to ask is: where does this energy come from? My assumption would be: the potential energy is only there because there is a distance between the magnet and the metal piece in the first place.

But this makes it sound just like gravity, which is a pretty f***ed concept on its own...

14. Permanent magnets'work' because the atoms are lined up in a certain orientation. In essence, their electon orbits are aligned to produce a magnetic field. Moving electrons and electric current are the same in this regard. The fields form the various electron orbits add up, and a magnetic field is produced.

Why does this cause an attraction to ferrous materials -- because it does. There may be some sort of explanation, but I don't really know what it is.

Magnetic force is a demonstration of one of the quasi perpetual motion concepts that actually exist. Electrons have been spinning around nucleii for quite some time-- and they will hopefully contine to keep spinning for qute a while yet. Probably not eternally, but for a long time. There is a concept called entropy that says that everything will eventually stop, but again, I don't think that we have to worry about it at this point.

As far as magnets continuing to work, they normally will if not disturbed.
Interestingly enough, they seem to maintain their magnetism longer if they are stuck to a piece of metal. Magnets are often supplied with metal 'keepers' for this purpose. However, this all has to do with the alignment of the atoms. The electrons keep spinning.

As far as magnets and perpetual motion -- well the magnet will jump to the metal, but how do you get it back off. Unfortunately you have to add some force. Generating the force to move the magnet away kind of screws up the perpetual motion concept.

I hope that I'm not coming across as snide. I've spent many years of my life thinking about magnetics, and I feel that I have a little understanding. I'm just trying to share my opinions.

ford2go

15. Sorry for not responding.

The magnets stick together through a particular method. Look at a magnetic field (Put a magnet under a piece of glass (anything actually), pour iron powder on top, and look at the shape that it has. You can see it as a fountain that sends its contents into the air, and due to gravity falls back down..but with magnets it falls back around to the back, and goes through the core in order to continue to process. It goes in a oval like loop on every side. Now, when you have a magnet N-S and bring it to N-S, they will attract; they do this because-the N field emits the energy (for our purposes) and the S brings it in, right? So when they are brought together, instead of the S field bringing in the N energy from itself from that distance, it has a N field right in front of it, and therefore prefers to get the energy from the closer source. So what happens to its own N field? since it can't go to its own S pole (since that depletion has already been fulfilled), it has to find somewhere else to go, so it travels along the sustaining surface of the magnet and reaches the 2nd magnets S pole so that that depletion zone can be fulfilled...hence 1 magnet from 2.

The problem with turning a group of magnets into a perpetual motion device is that even though you can push other magnets to create force, the fact that the energy recirculates will end up pulling back the kinetic energy that you gave the other magnet. I have a few theories for how to defy this....but thats for you to read in the USTPO's registry list in the mid-far future.

Also, the thing when you "give" a magnet energy is that you are using the EM field to give its electron field momentum, hence the flow. Once momentum has been created, constant instantaneous depletion zones (depletion of its electron field) allow the kinetic power of the field to continue...unless you alter it by exposing it to another material that can correspond to the magnets energy.

Note: A TREMENDOUS part of all sciences is based on depletion zones...if you are going to study/learn anything, then it should be on them. It is used in everything, from Biology, to chemistry, to physics...and even philosophy. It is a property of the universe itself. Without them, very few seemingly ordered objects could not exist.

And don't forget about electron attraction fields....that is equally important in understanding science; EA fields are the topic that religious people hate because it describes how every living organism was created.

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