Jump to content
Science Forums

Perpetual motion


Recommended Posts

I know this seems a bit silly, but I've got an idea using magnets that seems feasible, at least in my mind. I just haven't had time to try it. Is it truly impossible, or simply not yet done? Does perpetual motion break any laws of physics, or is it only not proven possible mathematically?

 

Note: I will move this to Inventions and gadgets when Tormod gets a reply to his guitar rig question. I didn't want to bump that down the list.

Link to comment
Share on other sites

Work can never be done with 100% efficiency. Work in never equals work out. There is always a loss of energy in the system. Thus it is always neccessary to introduce additional energy into any process in order to maintain it's operation. Thus it is not possible to perfom work without consuming energy. Thus perpetual motion violates the laws of physics.

Link to comment
Share on other sites

what freethinker describes is known as the 2nd law of thermodynamics. The idea that this disregards a perpetuum mobile is as follows:

spontaneous processes only occyr if the enthropy increases. Thus causes the system to lose energy E.

Now to put the system back in it's original state the same energy E has to put into the system.

So in principle if we do the energy conversion 2 times (in and out of the system) with perfectly no energy loss a perpetuum mobile can be build.

But The 2nd law also implicates (after some mathematical manipulatyions):

- The energy transfer of one system to another can never be 100% efficient.

 

Bo

Link to comment
Share on other sites

Originally posted by: Freethinker

Work can never be done with 100% efficiency. Work in never equals work out. There is always a loss of energy in the system. Thus it is always neccessary to introduce additional energy into any process in order to maintain it's operation. Thus it is not possible to perfom work without consuming energy. Thus perpetual motion violates the laws of physics.

 

A magnet and gravity can both perform a work function without any introduction of, or loss of any energy. Would you consider this an accurate statement?

Link to comment
Share on other sites

Originally posted by: Uncle Martin

A magnet and gravity can both perform a work function without any introduction of, or loss of any energy. Would you consider this an accurate statement?

A magnet consists of a mass in which the magnetic domains of most of the molecules are all oriented in the same direction. It requires energy to make this happen. Magnetic interactions (such as induction in wires moving thru a magnetic field) creates heat (energy loss). Magnetic polarization disapates with time (entropy).

 

Thus magnatism is like any other potential energy, it takes energy to get it there and it uses energy up (entropy) when it's effects are bing used.

 

For now I will leave Gravity to someone else.

Link to comment
Share on other sites

  • 3 weeks later...

I am new here and not really interested in this topic....but i did find this site posted by Janus20 in the test page forum. Maybe it could be of use to you in you theoretical quandry

 

www.thewebspert.com/cresswell/

 

[ED: Danger! This website calls up at least two ads and a blank window that appears to be downloading something. Use at your own risk. Pyro]

 

I didn't have time to read the whole page (quite large by the way) but it seems to be dealing with the subject that you are discussing. Hope it helps!

Link to comment
Share on other sites

Originally posted by: kerplunk

I am new here and not really interested in this topic....but i did find this site posted by Janus20 in the test page forum. Maybe it could be of use to you in you theoretical quandry

Hello Kerplunk. I hope you do find a topic of interest and join our discussions. We always enjoy new voices of reason.

I didn't have time to read the whole page (quite large by the way) but it seems to be dealing with the subject that you are discussing. Hope it helps!

Nor did I ahve time to do more than a quick review.

 

My approach to such sites is to start doing some fact checking at the beginning. If it starts getting things wrong early, I don't need to waste too much additional time. That is how I would classify this site.

 

e.g. "The diagram shows an iron transformer that has an unlaminated core. Contrary to popular belief, laminations do not directly improve the efficiency of transformer windings."

 

Perhaps this is an "what is 'is'" discussion? At lower frequencies especially, where E/I iron cores are used, they DO noticably increase a transformer's efficiency. If you take two coils at a given orientation with and without a core, there is a dramatic difference. If the width of the E/I laminated plates is correct, the efficiency compared to a solid core goes up. In fact, this used to be a regularly found problem. When power supplies designed with 60hz E/I cores are used in 50Hz countries they would overheat because of internal power comsumption (low coefficient of coupling). Now are they using "directly" to put some fudge factor in there? WHo knows. But the statement is not correct.

 

Further "The truth about WHY eddy currents occur naturally, remain unquestioned and therefore unanswered."

 

I learned the answer to this in High School Electronics! Simple wavelength related standing waves.

 

and then "Applying the Conservation of Energy (First law of Thermodynamics):

VI in = VI out + Eddy Current heat to cooling oil and this simplifies to: -"

 

This ignores loss in the windings themselves, which is frequency dependant, energy loss thru heat transfer TO the "cooling oil" and many other factors.

 

And this was only a couple of the errors found to that point.

 

At which point I stopped wasting my time there.

Link to comment
Share on other sites

I'd have to agree that I'm not aware of any way to actually demonstrate perpetual motion (although I always find it entertaining when people tell me about things that will never / always happen), but I think you are onto something with your magnet train of thought. While I was reading some marketing propaganda about hybrid vehicles the other day, it occurred to me that electromagnetics could reasonably improve transportation technology far more than any of the current alternative fuel implementations.

 

Consider the amount of energy generated from an electromagnet compared with the energy you must provide to power the electromagnet. As a crude example, if you were to place a number of electromagnets in a circle, then place a wheel with magnets attached to it inside the circle, would you be able to rotate the wheel simply by providing current to the electromagnets in sequential order?

I may be completely off base on this, but my rather juvenile powers of deduction are telling me that you might be able to dramatically increase the milage an automobile can achieve by lining your wheelwells and hubs with electromagnets and corresponding magnets. I couldn't give you a joule ratio for the potential delta in efficiency (sorry, not an EE) but it seems pretty straightforward to me.

Link to comment
Share on other sites

Originally posted by: nemo

As a crude example, if you were to place a number of electromagnets in a circle, then place a wheel with magnets attached to it inside the circle, would you be able to rotate the wheel simply by providing current to the electromagnets in sequential order?

I may be completely off base on this, but my rather juvenile powers of deduction are telling me that you might be able to dramatically increase the milage an automobile can achieve by lining your wheelwells and hubs with electromagnets and corresponding magnets. I couldn't give you a joule ratio for the potential delta in efficiency (sorry, not an EE) but it seems pretty straightforward to me.

I think you have just decribed an electric motor. My thought was similar, but with "permanent" magnets. I know this has been tried numerous times in the past, but powered flight didn't go so well the first few times around either. I think I could get something to spin without any external power scource for the life of the magnets, which is quite long. It has been pointed out that there are no actual permanent magnets, a bit of a misnomer there. Using the attraction and repulsion properties of like and unlike poles, timed just so, this seems feasible to me. Now all I need to do is find the time to actually give it a "whirl".

Link to comment
Share on other sites

I think we're all on the same page about the car idea, but just to make sure. Even if it did work and was more efficient energy wise, it still couldn't be a perpetual motion machine. The wheels would have to push against the ground to move the car and their contact with the ground would produce friction, which leads to frictional losses. You'd have to put energy into the system to maintain a constant angular velocity of the wheels, let alone produce an angular acceleration.

 

The real reason for brining this up is that it shows a general problem for perpetual motion machines. Mechanical machines the undergo a work cycle have parts that are in contact and that move relative to one another: this produces friction which results in a reduction in the system's mechanical energy. Thus, the system continues to lose energy, and, energy must be continually put into the system in order to keep it running. So if your idea has parts that are in contact and that move relative to one another, you might as well scrap it as far as being a perpetual motion machine is concerned.

 

As far as rotating magnets... Magnets have mass and we need to move them, which means we must apply a force to them. Applying a force to an object and having it move in response to that force is work. So we'd continue to do work on the magnet to keep it spinning. Energy is the ability to do work, and work and energy are equivalent. So we'd have to continue to put energy into the system to keep the magnets spinning. Thus, things with spinning magnets are not a perpectual motion machine candidate.

 

I should also point out that the real thing usually talked about is not perpetual motion, but rather a perpectual motion machine. Perpetual motion has already been achieved by nature. Photons released soon after the Big Bang have traveled for billions of years through space without any input of energy, and will continue to do so unless they run into something. The real trick is to try to get a work cycle out of a machine with the system having the same amount of available energy after the cycle as it did before the cycle, without adding any energy during the process.

Link to comment
Share on other sites

Perpetual motion is impossible because

 

1) every entity needs to be produced, fitted, started. The act of starting means that the motion is not perpetual backwards (so no infinite backwards motion)

 

2) every entity is subject to the laws of thermodynamics. Every system (on any scale) gets more disorganised as time passes (known as entropy). Any machine will eventually fail because it's parts will fall apart or break (or the elements in it will, for example, react with, say, air, and rust - or even just be prey to nuclear decay). The timescale may be long, but "perpetual" implies forever.

 

3) Power is needed. A perpetual motion device is assumes to provide its own power. This again is impossible. There is always a loss of power when any action is performed, and it is iot possible to regain 100% of this energy. you could build a secondary device to provide the remaining energy - which means that you need external power, which will not be perpetual.

 

Here is an interesting read on the subject:

 

Physics 101 For Perpetual Motion Inventors

http://www.lhup.edu/~dsimanek/museum/phys101.htm

Link to comment
Share on other sites

OK Unc, perhaps Tormod whould have posted the link here instead of starting a new thread (which violates the laws of thermodynamics by requirying an increase of complexity at Hypography by increasing the number of threads). But does this help explain why your magnetic machine would not work?

 

" Discussion of The Classic Magnetic Motor

 

... Why the fascination with magnetism? I think it's because most people, even those who have had physics and engineering courses, still are a bit mystified by how magnets work, so they are less likely to see flaws in a magnetic engine design. One such inventor tried to convince me that magnets have unlimited stored energy, or can tap unlimited energy from "somewhere". "Just look at those magnets on your refrigerator," he said. "They support themselves, doing work against the force of gravity forever, so they must have infinite energy capability.""

 

http://www.lhup.edu/~dsimanek/museum/cheng.htm

Link to comment
Share on other sites

Originally posted by: nemo

Consider the amount of energy generated from an electromagnet compared with the energy you must provide to power the electromagnet. As a crude example, if you were to place a number of electromagnets in a circle, then place a wheel with magnets attached to it inside the circle, would you be able to rotate the wheel simply by providing current to the electromagnets in sequential order?

As pointed out by Unc, this is basically an electric motor. But by your specific description, it is usually refered to as a "linear motor". Back in the day, when turntables ruled the audio world (oh for the good ole days) some companies developed this drive type for turntable. One attached a magnetic strip inside the platter and applied external magnetic force to "pull" this linear strip (attached at the ends to make a continous circle).

I may be completely off base on this, but my rather juvenile powers of deduction are telling me that you might be able to dramatically increase the milage an automobile can achieve by lining your wheelwells and hubs with electromagnets and corresponding magnets. I couldn't give you a joule ratio for the potential delta in efficiency (sorry, not an EE) but it seems pretty straightforward to me.

Another similar application of linear motor design to transportation is the "Maglev". This is a "train" design which includes superconductors to "levitate" the vehicle and a linear motor the length of the entire track which "positions" the train. By activating the magnetic coils in the appropriate order, the vehicle is moved.

 

"Fundamentals of Maglev"

 

http://www.calpoly.edu/~cm/studpage/clottich/fund.html

 

There is also the "rail gun". Which fires a metal object via magnetic pulses

 

"Railgun Construction"

 

http://www.railgun.org/

 

Or the "Coil Gun"

 

"The aim of this site is to present experimental research information on coilguns and related topics. In this capacity we hope to foster interest in the fields of physics and engineering. All significant developments will be posted.

 

Our long term objective is to design and construct single and multi-stage coilguns capable of firing projectiles at supersonic speeds.

 

http://www.coilgun.eclipse.co.uk/index.html

 

Bottom line, linear magnetic motor design is highly efficient but requires significant infrastructure. e.g. while it would be a highly efficient method of moving a "car", it would require some magnetic infrastructure running the entire length of the "road".

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
 Share

×
×
  • Create New...