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!