Physics question

[jeffsg4mac]

This is something I have often wondered about.

Is it theoretically possible to build a motor powered only by powerful permanent magnets? I have never heard about it being done, but it would seem, on the surface, that it would be possible to harness the power of the magnets to do work. If not then why?

 

[Alex2507]

Is it theoretically possible to build a motor powered only by powerful permanent magnets?

No.

If not then why?

Because.





It's slow today and I just couldn't help myself.

 

[MidnightSensi2]

This is something I have often wondered about.

Is it theoretically possible to build a motor powered only by powerful permanent magnets? I have never heard about it being done, but it would seem, on the surface, that it would be possible to harness the power of the magnets to do work. If not then why?

Not an easy answer - there are volumes and volumes of stuff talking about it. well, not that specifically, but, the physics behind ideas like that (I think what your talking about is perpetual motion)

But, I'll attempt to at least attempt to get something down that may help answer... it won't be 100% well stated because while I am a mechanical and composite engineer I haven't been in physics classes for a long time, my brain is mostly clogged with bong resin and malted hops, and I'll have to over simplify to answer before tomorrow comes (maybe someone else can do it more poetically) ....

Well, to get the permanent magnets to do work you'd need to provide something either to turn their poles (well, move them physically more practically...which would probably require more work than what they'd output).

But, a speaker, for example, works by using an electromagnet (so one magnet is a permanent magnet and the electromagnet is the coil where when we apply current from our amps it magnetizes metal around it, alternating from the positive to negative, creating the field which causes the speaker to move back and forth how we want it to). So, the input is the electrical signal from your amplifier.

Permanent magnets you could move around eachother, but there has to be some 'input'...since your trying to get work, you'd have to find some kind of source to convert it from.... wind, tides, petrol with a gas powered engine, whatever....because we can't /make/ energy, we can only transform it.

But, as far as I know, there would be no way to have just two magnets sit next to eachother and do 'work' (like move something, or power something, etc.)... because that would violate what we call the first law of thermodynamics: which is that energy in a system must remain constant.... or, energy can't be created or destroyed...it can only be transferred.

How we do 'work' (move, rotate, etc.) now is we get some amount of energy (potential energy) and then convert it in some way that is useful to us. But there are losses when you transfer energy. Like, an engine in a car is only about 15-20% efficient in transferring energy from the source (fuel) to the work (moving the drivetrain). (actually the most efficient mode of transportation energy wise is a bike hehe - like energy needed per distance)

It also would violate the second law of thermodynamics, which is a little more complex to understand, but it's basically that usable energy decreases overtime, or that chaos/disorder increases (we call this entropy). Entropy is a little harder to describe, there are mathematical ways to think about it and there are physical ways to think about it. Basically, it's the amount of disorder something has. This always increases.

I know that's getting a little sciency, but basically what I'm saying is that in any motor or way to create work, we can't make something from nothing. We have to put work in. When we talk about things like engines or motors, they aren't actually making anything, they are only transferring energy in one form to another...and they can't do it 100% efficiently, and when we do it, some disorder occurs from that. Because chaos/disorder is always increasing (entropy is always increasing).

To speed this up and prove it to yourself, you may have noticed that dropped magnets become less and less powerful. That's because when they are dropped the molecules on either pole and pushed in the opposite direction and eventually reach equilibrium.

Finally, the energy to get something magnetized also has to be accounted for.

(Yes, physicists talk about chaos increasing continually).

Now, THAT SAID, hehe... there are physicists who are looking for how to create perpetual motion...that is, something that violates the first and second law of thermodynamics.

 

[jeffsg4mac]

I was not exactly referring to perpetual motion as I am aware that the magnets would loose their energy over time. I was more interested in knowing of a self powered motor has ever been made by just using all permanent magnets.

I realize that in an electric motor the stator changes polarity as it spins inside the magnetic field. It would seem this could be duplicated by using all permanent magnets and having them flip their polarity on some sort of cam mechanism or some other way so that they are pushing and then pulling the stator magnets as it spins. That's what I was wondering about. Seems like an engineering feat but it seems plausible when thinking about harnessing the push/pull of the magnets.

 

[MidnightSensi2]

I guess the question is what powers the cam and does the energy it takes to move the cam render it very inefficient at transferring energy?

Always good to look into!

Don't always think big either. Like, what about those things in the subways and theme parts that count the number of people that walk in? The things you push and rotate to walk in.... use the people to turn the cam and rotate your magnets. I donno, hehe, brainstorming is how it starts

A friend of mine always says "nothing easier than something" about energy... he says have the employees take the damn stairs, "the secretary especially" haha.

 

[jeffsg4mac]

I am sure their are engineers and scientist that have thought about this forever. I just have never heard why it won't work or if it has ever been done on any scale.

 

[Seth=L]

I remember a scam built around this concept, I even watched a video about it. Unfortunately I don't remember the name of the video.

I'm not a physics major but I think I may be able to summize as to why such a device would not work. In order for a generator to work copper conductors must pass by an magnetic force in order to produce electricity. To perpetuate this it must do so repeatedly and naturally the larger the magnets and the more copper there is, the more power that can be produced.

There are many ways to create motion for a generator, the most common is by heat. The objective is turn a turbine in most large scale operations. The force from the heat must be greater than the opposing force from the mechanics of the generator. This includes gravity and magnetic fields. If you've ever taken a small electric motor and turned the post you can feel the force of the magnets inside because they are attracted to the iron that the copper is wrapped around.

In order for a magnetic driven turbine to perpetuate an external force other than magnetism must always be applied. Gravity and magnetism alone are simply not physically capable of perpetuating motion, as both are techically "stationary".

Now I could be incorrect or way off base, but I think this is the basic idea that was behind why magneticly perpetuated power is not possible.

 

[jeffsg4mac]

Seth,

That all sounds good and you are probably correct, but the fact that an electric motor runs by magnetism alone is what is confusing. Granted half of it is electromagnetism but it is magnetism none the less. The only difference between a permanent magnet and and electro magnet is that one has the magnetic field induced and the other is natural/man made.

It can't be a question of how powerful the magnets are because the electro magnets in say a small appliance motor are no more powerful than many permanent magnets. In fact I have worked with some permanent magnets that would take a finger off if you got between them and some metal surface.

 

[highfigh]

I was not exactly referring to perpetual motion as I am aware that the magnets would loose their energy over time. I was more interested in knowing of a self powered motor has ever been made by just using all permanent magnets.

I realize that in an electric motor the stator changes polarity as it spins inside the magnetic field. It would seem this could be duplicated by using all permanent magnets and having them flip their polarity on some sort of cam mechanism or some other way so that they are pushing and then pulling the stator magnets as it spins. That's what I was wondering about. Seems like an engineering feat but it seems plausible when thinking about harnessing the push/pull of the magnets.

What is the purpose of this motor- to start turning once it's physically moved and then create its own current to power itself? That sounds like a combination of a magneto and a motor, in the same chassis.

 

[KEW]

For a motor you have the ability to change the push-pull of the induced field so as to yield a continuous motion.
With "dumb" magnets, once their potential energy has been used, game over. In other words unless you are doing something to impart motion (inputting energy from a source outside of the simple magnets), you have a pretty short lived source of energy from the magnets.

In your example of a cam or whatever to reverse polarity, that physical motion is having to overcome the magnetic forces (which you could consider a net ZERO in energy gain/loss) plus you have the losses from the mechanical device involved, so you must end up with a net energy loss.

If you are willing to get loose with interpretation, you can liken the force of gravity to a magnetic field. Once something reaches the ground, there is no more energy available. Hydro plants work off of gravity, but are dependent on solar energy to evaporate the water so it can be "lifted" back to the higher elevation.

I know, pretty sloppy analogy, but the principals are the same.

 

[jeffsg4mac]

What is the purpose of this motor- to start turning once it's physically moved and then create its own current to power itself? That sounds like a combination of a magneto and a motor, in the same chassis.

No purpose really. Just curious if it can be done and if not why.

 

[jeffsg4mac]

In your example of a cam or whatever to reverse polarity, that physical motion is having to overcome the magnetic forces (which you could consider a net ZERO in energy gain/loss) plus you have the losses from the mechanical device involved, so you must end up with a net energy loss.

Ok that does make sense, but you would think if the mechanism was finely balanced and one set of magnets was stronger than the other it could be done. Like one set of magnets rocking back and forth out the way like rocker cams. I am just guessing.

 

[TLS Guy]

You are actually proposing an impossible perpetual motion machine.

In order to convert electrical energy to mechanical energy you have to feed the power in. You can not do that if the field and armature are permanent magnets.

In traditional motor there are is a wound armature and field windings. The best they can achieve 40% efficiency. However modern motors with very strong permanent rare Earth magnets can achieve in excess of 90% efficiency

The same applies to generators with permanent rare Earth armatures.

My Toyota Camry hybrid contains around 2 Kg of rare Earth metals in its motor and regenerative braking systems.

The rub is they are called rare Earth metals for a reason. They are rare and will soon be exhausted. By far the largest deposits are in China. The Chinese are becoming increasingly reluctant to share.

This metals are also essential ingredients of many electronic components now.

Building Hybrid, or electric cars and "green" electronic generators will be impossible without these rare Earth metals.

That is why NASA is proposing to catch an asteroid, which are believed to be rich in rare Earth metals. The astro physicist in charge is Paul Abel, who is a grad of UND, and son of a physician colleague I worked with in my years in Manitoba. We are still close friends and they visit us at Benedict a couple of times a year, and we visit them in While Rock BC.

Although this sounds like science fiction, Paul believes this to be a feasible and essential undertaking.

 

[jeffsg4mac]

The rub is they are called rare Earth metals for a reason. They are rare and will soon be exhausted. By far the largest deposits are in China. The Chinese are becoming increasingly reluctant to share.

Actually, your are mistaken on this one point. Rare earth magnets/metals are not rare at all. That is a misleading term. They are as common as lead or copper. They just don't appear in large concentrated quantities. The ore has to be extracted, processed and turned into magnets. This I remember form x-ray physics class Rare earth metals are used in the phosphor screens of CR.

Wiki- "The term "rare earth" can be misleading as these metals are not particularly rare or precious;[1][2] they are about as abundant as tin or lead.[3] Interest in rare earth compounds as permanent magnets began in 1966, when K. J. Strnat and G. Hoffer of the US Air Force Materials Laboratory discovered that YCo5 had by far the largest magnetic anisotropy constant of any material then known.[4]"

Wiki- "Despite their name, rare earth elements (with the exception of the radioactive promethium) are relatively plentiful in the Earth's crust, with cerium being the 25th most abundant element at 68 parts per million (similar to copper). However, because of their geochemical properties rare earth elements are typically dispersed and not often found in concentrated and economically exploitable forms known as rare earth minerals.[3] It was the very scarcity of these minerals (previously called "earths") that led to the term "rare earth".

 

[TLS Guy]

Actually, your are mistaken on this one point. Rare earth magnets/metals are not rare at all. That is a misleading term. They are as common as lead or copper. They just don't appear in large concentrated quantities. The ore has to be extracted, processed and turned into magnets. This I remember form x-ray physics class Rare earth metals are used in the phosphor screens of CR.

Wiki- "The term "rare earth" can be misleading as these metals are not particularly rare or precious;[1][2] they are about as abundant as tin or lead.[3] Interest in rare earth compounds as permanent magnets began in 1966, when K. J. Strnat and G. Hoffer of the US Air Force Materials Laboratory discovered that YCo5 had by far the largest magnetic anisotropy constant of any material then known.[4]"

Wiki- "Despite their name, rare earth elements (with the exception of the radioactive promethium) are relatively plentiful in the Earth's crust, with cerium being the 25th most abundant element at 68 parts per million (similar to copper). However, because of their geochemical properties rare earth elements are typically dispersed and not often found in concentrated and economically exploitable forms known as rare earth minerals.[3] It was the very scarcity of these minerals (previously called "earths") that led to the term "rare earth".

Neodymium and Samarium, are not that easily found in quantity. In order to mine it you have to have a reasonable concentration in one place. You can't turn over the entire Earth's surface to mine it. We are consuming these metals at a fast rate. The lions share of the exploitable concentrations are in China.

 

[Stereodude]

Is it theoretically possible to build a motor powered only by powerful permanent magnets? I have never heard about it being done, but it would seem, on the surface, that it would be possible to harness the power of the magnets to do work. If not then why?

No because a motor requires a moving magnetic field in order to turn the rotor. If you only used permanent magnets you couldn't have the moving magnetic field that pushes / pulls the rotor along.

 

[Rickster71]

This is something I have often wondered about.

Is it theoretically possible to build a motor powered only by powerful permanent magnets? I have never heard about it being done, but it would seem, on the surface, that it would be possible to harness the power of the magnets to do work. If not then why?

Assuming that the Solar Panel and Wind Turbine Companies won't shoot you and/or buy your patent and bury it somewhere.....No it won't work.
The best you could hope for is something like the chrome paper weights with the metal ball that hangs and a magnet keeps it spinning in circles.
The motor would spin, but as soon as a load was applied it would stop.

 

[jeffsg4mac]

As I said I am no engineer but here is my idea so tear it apart and tell my why it won't work.

You have three pieces. An inner ring, an outer ring and a larger outer ring. The inner ring spins and has magnets placed around it with all the same poles facing outwards. The next ring is connected buy gearing that causes it to spin the opposite direction. The third ring is fixed and has magnets placed with a N, and S near each other pointing at the inner most ring. The middle ring is a series of shields that are timed with the rotation of the inner ring. As an inner magnet is drawn towards an outer magnet the shielding is coming into place so that the next magnet can push it without interference from the adjacent magnet. Follow me?

 

[highfigh]

No because a motor requires a moving magnetic field in order to turn the rotor. If you only used permanent magnets you couldn't have the moving magnetic field that pushes / pulls the rotor along.

As soon as the armature passed the poles of the magnets, current would be induced since it doesn't matter if the magnetic field or the armature that's saturated by the field is moving. That's the principle behind alternators with only one wire- it starts supplying the charging voltage/current as soon as it begins to rotate.

 

[TLS Guy]

As I said I am no engineer but here is my idea so tear it apart and tell my why it won't work.

You have three pieces. An inner ring, an outer ring and a larger outer ring. The inner ring spins and has magnets placed around it with all the same poles facing outwards. The next ring is connected buy gearing that causes it to spin the opposite direction. The third ring is fixed and has magnets placed with a N, and S near each other pointing at the inner most ring. The middle ring is a series of shields that are timed with the rotation of the inner ring. As an inner magnet is drawn towards an outer magnet the shielding is coming into place so that the next magnet can push it without interference from the adjacent magnet. Follow me?

Your problem is you have no source of energy. Magnets by themselves can not produce energy.

So if you spun your system to get it going, energy would be quickly absorbed not only in the gearing, but in eddy currents induced in the magnets and released as heat.

So quickly the N/S poles would line up and you motor would stop.