# Thermodynamics of magnets (layman version, please)

PBE6
Science 15 Sep '09 15:24
1. PBE6
Bananarama
15 Sep '09 15:24
Just wondering if anyone is familiar with the thermodynamics of magnets. I recall seeing a discussion on them here a few months, but for the life of me I can't remember which thread it was in. The reason I'm asking is that a friend of mine has seen some dubious adds about magnets that make "free energy" and "run the generator forever", i.e. obvious crap. I tried explaining the 2nd law to him, and why no machine will ever run forever and give you free energy, but he doesn't have a science background so it's not sinking in. Suggestions?
2. 15 Sep '09 15:473 edits
Thermodynamics of magnets is a bit tricky, because permanent magnets are strictly speaking not in equilibrium so thermodynamics does not (fully) apply.

Anyways, if you're looking for a reason why a perpetuum mobile cannot exist, you're wasting your time. It's simply an axiom of thermodynamics (as the second law is one of those axioms).
3. PBE6
Bananarama
15 Sep '09 15:57
Originally posted by KazetNagorra
Thermodynamics of magnets is a bit tricky, because permanent magnets are strictly speaking not in equilibrium so thermodynamics does not (fully) apply.

Anyways, if you're looking for a reason why a perpetuum mobile cannot exist, you're wasting your time. It's simply an axiom of thermodynamics (as the second law is one of those axioms).
I tried explaining to him how a machine like a heat pump can appear to provide free energy because a small energy input by you gets you a bigger energy output courtesy of a large hear reservoir, but that this energy is not free because the heat reservoir will eventually be depleted unless it gets recharged. I wanted to use a similar analogy for magnets, but I'm not really sure how they get "charged" or "depleted" during use.
Baby Gauss
15 Sep '09 22:05
Originally posted by PBE6
I tried explaining to him how a machine like a heat pump can appear to provide free energy because a small energy input by you gets you a bigger energy output courtesy of a large hear reservoir, but that this energy is not free because the heat reservoir will eventually be depleted unless it gets recharged. I wanted to use a similar analogy for magnets, but I'm not really sure how they get "charged" or "depleted" during use.
5. 16 Sep '09 07:20
Originally posted by PBE6
I tried explaining to him how a machine like a heat pump can appear to provide free energy because a small energy input by you gets you a bigger energy output courtesy of a large hear reservoir, but that this energy is not free because the heat reservoir will eventually be depleted unless it gets recharged. I wanted to use a similar analogy for magnets, but I'm not really sure how they get "charged" or "depleted" during use.
Magnetic fields do no work.
6. uzless
The So Fist
18 Sep '09 18:38
Originally posted by PBE6
Just wondering if anyone is familiar with the thermodynamics of magnets. I recall seeing a discussion on them here a few months, but for the life of me I can't remember which thread it was in. The reason I'm asking is that a friend of mine has seen some dubious adds about magnets that make "free energy" and "run the generator forever", i.e. obvious crap. I t ...[text shortened]... e energy, but he doesn't have a science background so it's not sinking in. Suggestions?
Different question.

If you carefully placed a bunch of magnets in a cirlce but slightly angled them offset in a circulular direction with the positive ends all pointing towards the centre, then placed a positively charged ball in the centre, the ball would move around in a circle continuously. Correct?

The ball is constantly being repelled by the ends of the magnet. If this is not correct, then explain why the ball would stop being repelled by the magnets.
7. sonhouse
Fast and Curious
18 Sep '09 18:46
Originally posted by uzless
Different question.

If you carefully placed a bunch of magnets in a cirlce but slightly angled them offset in a circulular direction with the positive ends all pointing towards the centre, then placed a positively charged ball in the centre, the ball would move around in a circle continuously. Correct?

The ball is constantly being repelled by the ends ...[text shortened]... et. If this is not correct, then explain why the ball would stop being repelled by the magnets.
The flaw there is the 'positive charge' idea. When you say positive charge, most people think of electric charges, and there is no mutual attraction or repulsion of electric V magnetic charges.
If you are talking about positive (North pole?) 'charged' ball you would be talking about monopoles which so far have not been found in nature, some evidence of monopole analogs have shown up but even so, there would only be a movement to an equilibrium point after which no more movement is possible because the magnetic fields are unvarying. We only can extract work from varying fields which takes energy so it's only a conversion of one form of energy to another, say, electric to kinetic or some such. DC fields are incapable of generating energy for any longer than it takes to reach an equilibrium.
8. uzless
The So Fist
18 Sep '09 19:19
Originally posted by sonhouse
The flaw there is the 'positive charge' idea. When you say positive charge, most people think of electric charges, and there is no mutual attraction or repulsion of electric V magnetic charges.
If you are talking about positive (North pole?) 'charged' ball you would be talking about monopoles which so far have not been found in nature, some evidence of mo ...[text shortened]... ds are incapable of generating energy for any longer than it takes to reach an equilibrium.
ok, let me rephrase.

Instead of a cirlce. let's just make a circle full of magets with the north poll sides all facing the middle. Each length of magnet is different so the mag field around each magnet extends a different distance into the centre of the circle and some fields overlap each other (fields are always in conflict with one another).

Now, you place a ball with a south pole in the centre of the sphere, and the north pole on the outside of the sphere.

Now, you place the ball in the centre of the magnets. What happens?
9. sonhouse
Fast and Curious
19 Sep '09 01:36
Originally posted by uzless
ok, let me rephrase.

Instead of a cirlce. let's just make a circle full of magets with the north poll sides all facing the middle. Each length of magnet is different so the mag field around each magnet extends a different distance into the centre of the circle and some fields overlap each other (fields are always in conflict with one another).

Now, y ...[text shortened]... tside of the sphere.

Now, you place the ball in the centre of the magnets. What happens?
It's a good thing it's not a cirlce, I have had a very hard time trying to get that configuration🙂 The thing that screws up your effort is the magnetic fields themselves: If you have a bunch of north poles all facing each other, distance different or not, you have to visualize what happens to the resultant field, it's like a bush or tree, the fields extend out to each other and make a self repelling field 'bush' that pushes the field lines up and out of the circle, which btw, you changed to 'Sphere', which I assume you mean circle. I have seen demo's of your attempt but all it does is like putting a ball at the top of a hill and letting go, it may move downhill alright but only once, you have to resupply energy to get it back to the top of the hill or magnetic configuration you entered at first. It won't do more than maybe make one circuit of the other magnets before coming to rest somewhere but that is not a demo of free energy, just a ball falling downhill for a ways. Besides, if you have the south pole aiming, I presume perpendicular to the north poles it would be attracted to the strongest field first but unless you have it confined really well, the poles would align 90 degrees and probably stick to the nearest magnet, the poles would flip. You would probably have to have some configuration that constrained the central magnet from flipping, like on a track or something. It still would just be like a ball falling down a slope due to gravity, it would just make a circuit and stop. You would also notice the south pole not wanting to be in the center so you would have to constrain it yourself or have it in a track or something.
10. uzless
The So Fist
21 Sep '09 19:153 edits
Originally posted by sonhouse
It's a good thing it's not a cirlce, I have had a very hard time trying to get that configuration🙂 The thing that screws up your effort is the magnetic fields themselves: If you have a bunch of north poles all facing each other, distance different or not, you have to visualize what happens to the resultant field, it's like a bush or tree, the fields extend e center so you would have to constrain it yourself or have it in a track or something.
I meant the ball is the sphere.

In the centre of the ball is the south pole and on the outside of the sphere/ball you have the north pole.. Think golf ball with an inner and outer core.

By placing the magnets in a circle with different lengths, i was trying to get across the point that if you placed the sphere/ball inside this circle, the sphere/ball would be pushed away by all the magnets. Since the lengths are shorter/longer, the magnetic field for each magnet would be push the ball/sphere away at varying strengths.

In other words, the sphere/ball would move around inside the circle indefinitely, never being able to get out of the cirlce but always being pushed in some random direction.

A perpetual motion device!

Now, place a generating device under the whole contraption that works on compression so that as the ball rolls over it, it converts the compression to electricity!

A perpetual energy Device!!

😉

P.S. Please remit 10% of your profits to me. I retain all intellectual rights.
11. 22 Sep '09 04:46
Originally posted by uzless
I meant the ball is the sphere.

In the centre of the ball is the south pole and on the outside of the sphere/ball you have the north pole.. Think golf ball with an inner and outer core.

By placing the magnets in a circle with different lengths, i was trying to get across the point that if you placed the sphere/ball inside this circle, the sphere/ball w ...[text shortened]...

😉

P.S. Please remit 10% of your profits to me. I retain all intellectual rights.
I believe it would quickly find its most stable place or equilibrium and stop.
12. uzless
The So Fist
22 Sep '09 18:46
Originally posted by joe beyser
I believe it would quickly find its most stable place or equilibrium and stop.
not if you placed each magnet on a little pin (like a compass needle that floats) that would allow the magnet to move as it was pushed by the field around the ball as the ball moved closer.

This would allow for constantly changing magnetic fields so there would never be a stable equilibrium spot.
13. 22 Sep '09 19:14
Originally posted by uzless
not if you placed each magnet on a little pin (like a compass needle that floats) that would allow the magnet to move as it was pushed by the field around the ball as the ball moved closer.

This would allow for constantly changing magnetic fields so there would never be a stable equilibrium spot.
No it wouldn't.
14. uzless
The So Fist
24 Sep '09 20:221 edit
Originally posted by KazetNagorra
No it wouldn't.
the ball/sphere would never stop. As it moved it would "push" the magnets near it to a different location. The magnets would push the sphere in a different direction and it would continue the cycle.

I'm going to build one.

Anyone know where I can get a magnetic sphere??
15. uzless
The So Fist
25 Sep '09 18:292 edits
Success!

Yesterday I went down the local hardware shop and bought a piece of plywood, 20 rectangle magnets and some small pins and glue. I built my contraption exactly as I said above. The hard part was finding a magnetic sphere but the local industrial supply store had a few.

So, the result so far....

I placed the sphere inside my circle of magnets and quickly realized the table i placed my contraption on was not level so the sphere just rolled to one side and stayed there.

So, out came the level and some shims....10 minutes later we were set for attempt 2.

As soon as i placed the sphere in the centre of the circle the magnets started to move randomly back and forth as I predicted...i released the sphere and gave it a slight push for some momentum. I must have watched the sphere move around inside the cirlce for about 2 minutes (slowly) before one of the magnets fell off its pin and stopped the experiment.

What i've found i think is that the sphere weighs too much. I need to find a slightly lighter sphere that will react quicker and faster. I also discovered i need a better way to attach the magnets to the pins without restricting the movement of the magnets too much.

Then all i need is a compression electricty generating device to run under the sphere. Friction will be a problem.

Anyone care to lend some venture capital my way?