Curious device

[exchemist]

1 hour ago, Prajna said:

Ok, I hadn't really associated chemical bonds with electrostatics (which I tend to associate with Van de Graff generators and rubbing cats on perspex rods, etc) but I'll accept that chemical bonds are electrostatic.

All the thinking about this device began while watching one of Robert Murray-Smith's early videos where he was discussing Wesley Gary's magnetic motor. He showed that if you place a thin keeper across the poles of a horseshoe magnet then if the keeper is longer than the span between the poles you will get additional poles that appear on the ends of the keeper due to flux leakage. If you then lift one end of the keeper off its pole the pole on the end of the keeper reverses.

The way I interpret what is happening with the keeper is by thinking in terms of magnetic currents. As I see it, a magnet is always trying to close its circuit. Really it is a perpetual motion machine all by itself. There is a large magnetic reluctance in the air but the magnet will complete the circuit will complete itself via the air if there is no path with more permittivity available. The keeper offers a low reluctance path but if it is too thin to contain the full magnetic current then some leaks through the air surrounding the keeper. That leakage flux will be of the same polarity as the pole it is next to. When one end of the keeper is lifted off its pole you have effectively turned your magnet-and-keeper into one long bar magnet (or a kinky horseshoe magnet in this case) and the keeper becomes one end of that magnet - the opposite pole to the one it presented due to leakage flux.

In my terms, a magnet will attract any object that offers a lower reluctance path than whatever is allowing it to complete its circuit currently (if you'll excuse the pun), that a magnet always completes its circuit via the shortest path with the lowest reluctance and the circuit is always closed. This need to reduce the length and reluctance of the magnet's circuit is what we observe as magnetic attraction.

Now this understanding of magnetism may well be wrongheaded but it seems to me to offer a much better description of magnetism than the classical scientific one you offered, which doesn't really tell us anything about how magnets behave.

I think Ed Leedskillin was the only guy who understood magnets but then nobody can understand Leedskillin (including me.)

OK I understand what you mean and I'm aware there is a "magnetic circuit" model used in engineering: https://en.wikipedia.org/wiki/Magnetic_circuit 

However this has drawbacks if used incautiously, as is in fact mentioned in the article. There is in truth no magnetic "current", as nothing flows. Whilst we habitually draw flux lines with arrows on, these do not indicate a flow of anything. The magnetic field is a vector field, i.e. it has both a magnitude and a direction at any point in space. The density of flux lines is used to denote magnitude and the arrows denote direction. That is all the arrows mean. A field is not a current. (This is explicitly stated in the section of the Wiki article subtitled "limitations".)

As for whether this way of thinking of magnetism is a better description, we have just seen how it has given you the wrong answer, in the example of the magnet stuck to a beam. So clearly it has severe limitations. The circuit model may be fine for analysing the shape of the field in electrical machines and so forth but, as with many models in science, it has limits and if these are not borne in mind it can make you look a bit of a berk! 😀

I had not heard of Ed Leedskalnin (not Leedskillin), but I see he was a Latvian immigrant to the USA who was active in  magnetism between the wars. I also see that indeed he was on the right track in interpreting magnetism as arising from circulation of charges within the substance, just as I described to you in my previous post. His understanding was thus a foreshadowing of what we understand today about magnetism from atomic theory, quantum physics and quantum chemistry. (Quantum theory was developed in the late 1920s and 1930s, possibly a little later than when he was writing about magnetism.) 

P.S. Curious fact: magnetism can in fact be shown to arise as a consequence of applying the theory of special relativity to electric charges in relative motion. I think that is rather cool. 

Edited April 16 by exchemist

[Prajna]

6 minutes ago, exchemist said:

OK I understand what you mean and I'm aware there is a "magnetic circuit" model used in engineering: https://en.wikipedia.org/wiki/Magnetic_circuit 

However this has drawbacks if used incautiously, as is in fact mentioned in the article. There is in truth no magnetic "current", as nothing flows. Whilst we habitually draw flux lines with arrows on, these do not indicate a flow of anything. The magnetic field is a vector field, i.e. it has both a magnitude and a direction at any point in space. The density of flux lines is used to denote magnitude and the arrows denote direction. That is all the arrows mean. A field is not a current. (This is explicitly stated in the section of the Wiki article subtitled "limitations".)

As for whether this way of thinking of magnetism is a better description, we have just seen how it has given you the wrong answer, in the example of the magnet stuck to a beam. So clearly it has severe limitations. So the circuit model may be fine for analysing the shape of the field in electrical machines and so forth but, as with many models in science, it has limits and if these are not borne in mind it can make you look a bit of a berk! 😀

  

Ok, I'll get on to reading that wiki article shortly but let me first attempt to outline more clearly and completely my theory (rather hypothesis) on magnetism:

1. All matter contains two magnetic poles that normally coincide.

2. In some substances it is possible to separate the magnetic poles in which case a 'magnet' is created. (perhaps this is possible with all substances, just we don't know how to do it yet). In ferrous metals, for instance, we can do this by exposing them to a magnetic field. I'm talking here on a macro level, there may be a far more adequate description at the atomic scale, your description of the alignment of magnetic domains being an example, but let's stick to considering it at the level of magnetic circuits for the moment.

3. When a magnet is created by separating the normally coincident poles a magnetic current is created, one 'leg' of which circuit runs between the two poles inside the, now, magnetic material. The other leg tries to complete the circuit via the shortest, lowest reluctance path it can find, normally the air surrounding the magnet,though this is a very high reluctance path but if there is no better path then it will do that; the circuit has to be complete whatever the circumstances are, you can't have an open magnetic circuit, according to my theory, which is why a monopole cannot exist (except I recently noticed an article that suggested magnetic monopoles have been created, oh well, maybe).

4. If the magnet, with its magnetic stress from the pole separation, is close to something that offers a lower reluctance path than the air then the magnet will try to include that object in its circuit, attracting said object to itself in order to shorten the path: what we see as magnetic attraction.

5. When we bring two magnets together with like poles  facing both magnets we have really joined both circuits so that there are now four 'legs' to the circuit: the shortest, lowest reluctance legs running between the two poles in each separate magnet; the high reluctance, longest leg, between the extreme ends of the two magnets; and a leg interposed between the two magnets.

6. When we bring two opposite poles together what we are really doing is adding to the magnetic stress in the magnets, effectively further separating their magnetic poles. Now each magnet finds it more difficult to complete its circuit since the 'like' pole is adding to the reluctance in the 'outside' leg.

So the magnet sticking to the beam is explained by the magnet trying to incorporate a low reluctance path and make that path as short as possible. For any faults this explanation contains, for me at least, it offers a useful way of understanding the behaviour of magnets. If it makes me look like a berk then no matter, I'm sure there is always a place for a free-energy-berk-crank, at least in some people's affections.

(was replying via my phone earlier, which is why my explanation was less clear)

[exchemist]

12 hours ago, KJW said:

The design to which I am referring was also a perpetual motion machine of the 2nd kind. It consisted of a large diameter pipe radiating thermal radiation at room temperature, this radiation being focused onto a smaller diameter pipe, the increased intensity resulting in an elevated temperature of the smaller diameter pipe. I could see nothing wrong with this design and was forced to conclude that it is impossible to focus radiation to an image that is brighter than the source. I raised this on a forum I regularly visited at the time, and my hypothesis was confirmed by another member.

 

I suppose that depends on what is meant by "brighter". In terms of radiation intensity, I'd have thought one could increase that beyond the intensity of the source, if it is an extended source. But clearly one can't change the frequency of the photons merely by focusing a beam, so the effective temperature (if is black body radiation) of the radiation can't be altered. in that way. Is that what you meant? 

43 minutes ago, Prajna said:

Ok, I'll get on to reading that wiki article shortly but let me first attempt to outline more clearly and completely my theory (rather hypothesis) on magnetism:

1. All matter contains two magnetic poles that normally coincide.

2. In some substances it is possible to separate the magnetic poles in which case a 'magnet' is created. (perhaps this is possible with all substances, just we don't know how to do it yet). In ferrous metals, for instance, we can do this by exposing them to a magnetic field. I'm talking here on a macro level, there may be a far more adequate description at the atomic scale, your description of the alignment of magnetic domains being an example, but let's stick to considering it at the level of magnetic circuits for the moment.

3. When a magnet is created by separating the normally coincident poles a magnetic current is created, one 'leg' of which circuit runs between the two poles inside the, now, magnetic material. The other leg tries to complete the circuit via the shortest, lowest reluctance path it can find, normally the air surrounding the magnet,though this is a very high reluctance path but if there is no better path then it will do that; the circuit has to be complete whatever the circumstances are, you can't have an open magnetic circuit, according to my theory, which is why a monopole cannot exist (except I recently noticed an article that suggested magnetic monopoles have been created, oh well, maybe).

4. If the magnet, with its magnetic stress from the pole separation, is close to something that offers a lower reluctance path than the air then the magnet will try to include that object in its circuit, attracting said object to itself in order to shorten the path: what we see as magnetic attraction.

5. When we bring two magnets together with like poles  facing both magnets we have really joined both circuits so that there are now four 'legs' to the circuit: the shortest, lowest reluctance legs running between the two poles in each separate magnet; the high reluctance, longest leg, between the extreme ends of the two magnets; and a leg interposed between the two magnets.

6. When we bring two opposite poles together what we are really doing is adding to the magnetic stress in the magnets, effectively further separating their magnetic poles. Now each magnet finds it more difficult to complete its circuit since the 'like' pole is adding to the reluctance in the 'outside' leg.

So the magnet sticking to the beam is explained by the magnet trying to incorporate a low reluctance path and make that path as short as possible. For any faults this explanation contains, for me at least, it offers a useful way of understanding the behaviour of magnets. If it makes me look like a berk then no matter, I'm sure there is always a place for a free-energy-berk-crank, at least in some people's affections.

(was replying via my phone earlier, which is why my explanation was less clear)

Apart from the bit about separating coincident poles, which seems to make little sense, this may work fine for you, for macroscopic magnetic or magnetised objects. The weakness is it can't connect macroscopic behaviour to what goes on at the atomic level or connect magnetism to other scientific phenomena. So it's basically reverting to a c.19th, pre-atomic theory, picture.  I've seen this before with some people from an engineering background on science forums. I suppose they prefer the mastery of nature which c.19th physics seemed to achieve, before the inconvenience of the invariance of the speed of light, the ultraviolet catastrophe and the photo-electric effect forced a rethink.

If you are happy with staying in a sort of steampunk, H G Wells era world, well OK. Most of us prefer deeper explanations, that connect to other scientific phenomena.

 

[Prajna]

1 hour ago, exchemist said:

I suppose that depends on what is meant by "brighter". In terms of radiation intensity, I'd have thought one could increase that beyond the intensity of the source, if it is an extended source. But clearly one can't change the frequency of the photons merely by focusing a beam, so the effective temperature (if is black body radiation) of the radiation can't be altered. in that way. Is that what you meant? 

Apart from the bit about separating coincident poles, which seems to make little sense, this may work fine for you, for macroscopic magnetic or magnetised objects. The weakness is it can't connect macroscopic behaviour to what goes on at the atomic level or connect magnetism to other scientific phenomena. So it's basically reverting to a c.19th, pre-atomic theory, picture.  I've seen this before with some people from an engineering background on science forums. I suppose they prefer the mastery of nature which c.19th physics seemed to achieve, before the inconvenience of the invariance of the speed of light, the ultraviolet catastrophe and the photo-electric effect forced a rethink.

If you are happy with staying in a sort of steampunk, H G Wells era world, well OK. Most of us prefer deeper explanations, that connect to other scientific phenomena.

 

Well, I don't claim it to be a comprehensive explanation (just that the one I outlined above is more complete than the previous offering). I'm trying to present a (albeit much simplified) way of looking at magnetism that, perhaps, helps to understand what is happening with magnets. Thanks for the pointer to the wiki article, very interesting, particularly the idea of gyrators, which I had not come across previously. Gyroscopic effects being another favourite of free energy cranks, btw.

The idea of pole coincidence is to explain how a magnet comes into existence and, in my model, represents the 'ideal' state of a material, exhibiting no magnetic properties outside the material itself. When the poles become separated, by whatever means, the material is constantly trying to return to that ideal state with its poles again coincident. If it can't do that then the next best thing is for it to complete its magnetic circuit in the most efficient manner - by the shortest, lowest reluctance path, including by attracting any ferromagnetic material in its local environment into a position where it offers the shortest path for the 'outside leg' of the circuit.

Sure, this description doesn't attempt to reconcile with other models of EMF and MMF and falls short of attempting to incorporate formulae with which to quantify it, but it is simple and sufficient to understand magnetism on a broad level, much as using water flow in a plumbing system to illustrate the principles of electric circuits.

Using it I can explain the interaction between the fingers on my rotor and the opposed magnetic poles in the rocker magnets by saying that when a finger is interposed between the magnets the magnets are offered a path by which they can reduce the stress in their magnetic fields by taking the path offered by the ferromagnetic properties of the finger - lower reluctance and a shorter path for the 'outside leg' of the magnets - thus attracting to the finger where they were otherwise repelling each other. It may not be a 'scientific' explanation but it is not 'wrong'.

[exchemist]

1 minute ago, Prajna said:

Well, I don't claim it to be a comprehensive explanation (just that the one I outlined above is more complete than the previous offering). I'm trying to present a (albeit much simplified) way of looking at magnetism that, perhaps, helps to understand what is happening with magnets. Thanks for the pointer to the wiki article, very interesting, particularly the idea of gyrators, which I had not come across previously. Gyroscopic effects being another favourite of free energy cranks, btw.

The idea of pole coincidence is to explain how a magnet comes into existence and, in my model, represents the 'ideal' state of a material, exhibiting no magnetic properties outside the material itself. When the poles become separated, by whatever means, the material is constantly trying to return to that ideal state with its poles again coincident. If it can't do that then the next best thing is for it to complete its magnetic circuit in the most efficient manner - by the shortest, lowest reluctance path, including by attracting any ferromagnetic material in its local environment into a position where it offers the shortest path for the 'outside leg' of the circuit.

Sure, this description doesn't attempt to reconcile with other models of EMF and MMF and falls short of attempting to incorporate formulae with which to quantify it, but it is simple and sufficient to understand magnetism on a broad level, much as using water flow in a plumbing system to illustrate the principles of electric circuits.

Using it I can explain the interaction between the fingers on my rotor and the opposed magnetic poles in the rocker magnets by saying that when a finger is interposed between the magnets the magnets are offered a path by which they can reduce the stress in their magnetic fields by taking the path offered by the ferromagnetic properties of the finger - lower reluctance and a shorter path for the 'outside leg' of the magnets - thus attracting to the finger where they were otherwise repelling each other. It may not be a 'scientific' explanation but it is not 'wrong'.

Perhaps a short digression into the philosophy of science is appropriate. Science develops models of nature that enable correct predictions of the behaviour of nature to be made. Very often these models are recognised as approximate or incomplete and thus to have a certain scope of application which should not be exceeded. Newtonian mechanics is a good example. Nobody says Newtonian mechanics is "wrong" but it doesn't work at the atomic scale, nor when relative speeds are a significant fraction of c. We all know this and use Newtonian mechanics with those limits in mind. The magnetic circuit model is evidently quite successful for many engineering purposes, provided one doesn't stretch the analogy of its fictitious magnetic "current" too far. It is a scientific model insofar as it makes correct predictions for how nature will behave.

If your model tells you a static magnet continually does work, though,  you have a major problem, because you need to explain where this energy appears, what its source is and why this source never runs out. So at that point your model fails. 

[KJW]

1 hour ago, Prajna said:

ferromagnetic properties of the finger

Have you taken into account the hysteresis exhibited by ferromagnetic materials?

 

 

[Prajna]

15 minutes ago, exchemist said:

Perhaps a short digression into the philosophy of science is appropriate. Science develops models of nature that enable correct predictions of the behaviour of nature to be made. Very often these models are recognised as approximate or incomplete and thus to have a certain scope of application which should not be exceeded. Newtonian mechanics is a good example. Nobody says Newtonian mechanics is "wrong" but it doesn't work at the atomic scale, nor when relative speeds are a significant fraction of c. We all know this and use Newtonian mechanics with those limits in mind. The magnetic circuit model is evidently quite successful for many engineering purposes, provided one doesn't stretch the analogy of its fictitious magnetic "current" too far. It is a scientific model insofar as it makes correct predictions for how nature will behave.

If your model tells you a static magnet continually does work, though,  you have a major problem, because you need to explain where this energy appears, what its source is and why this source never runs out. So at that point your model fails. 

Useful digression, thanks. My model says a magnet is always trying to complete its outside leg circuit by the shortest, lowest reluctance path. Therefore energy is not being created or destroyed, simply that there is a force whenever poles are separated and the force is attempting to reduce the 'size' of the circuit. As a gap between magnets is increased then the intensity of the force drops off (per the inverse square of the distance), and the converse. The 'energy source' never runs out because the force is always present when poles are separated. We can consider a weak magnet to have barely separated poles and a strong magnet to have (comparatively) widely separated poles; I'm not talking here of actual physical separation but just as a metaphorical way if considering it. When we separate two magnets there is a force between them in much the same way that if we lift something against gravity we are storing potential energy in the object. If the magnets are free to move then they will snap together (or fly apart if like poles are opposed) in the same way that when we drop an object its potential energy is converted to kinetic energy.

In my device then, in terms of this model, with the rockers in the starting position, the magnets on the right are in the best arrangement (in terms of their magnetic field stress) they can achieve given the geometry in which they are restrained. Those on the left, because they are opposed with no mutual reluctance path, are arranged (limited by the restraining geometry) to the position where they offer the least obstruction to each other's magnetic circuit. If the rotor is turned 20 degrees then the situation is reversed and the magnets will rotate the rockers into the opposite configuration. No energy is created here, just sufficient energy has been input into the system to rotate the rotor, removing the finger from one gap and introducing a finger into the opposite gap. The movement is effected by the strength of the magnetic fields between the magnets. Using more powerful magnets should increase power out put but would also increase the eddy current drag on the rotor fingers, increasing the force required to turn the rotor. It is likely that the eddy current drag is always proportional to the magnet strength, I don't know and really it is this unknown that prompted me to post about the device here. This is what I need to understand, either practically by building and testing or, as I hoped to attain here, through an understanding of eddy currents and how they relate to field strength. Perhaps it is time for me to go look into transformers.

By the way, another influence on the required rotor torque is that the finger will be attracted into the field as it approaches and dragged back towards the field as it exits but I don't include these effects since they should be symmetrical. If you can think of other influences on the magnitude of the required rotor torque then I would be interested to consider them (excluding such obvious and trivial things such as friction in the axle bearing).

1 minute ago, KJW said:

Have you taken into account the hysteresis exhibited by ferromagnetic materials?

 

 

Thanks @KJW, it has been in the back of my mind. I have considered that there will be a reaction time between the finger exiting the gap and the magnets exerting their force on the rockers. It may be that at high rotation speed on the rotor the rocker arms may 'stall', or flutter rather than exhibit their full movement. The problem is that this is still a thought experiment, since I haven't built a device yet, so many things are just suppositions; things I have considered but only been able to come up with the best opinion I can achieve with my current practical and theoretical experience and a bit of reasoning based on that.

[swansont]

The work in this system would be provided by whatever is turning the input rotor. Nothing inside the device is supplying energy; there are only losses to be found there.

[Prajna]

10 minutes ago, swansont said:

The work in this system would be provided by whatever is turning the input rotor. Nothing inside the device is supplying energy; there are only losses to be found there.

Turning the rotor merely provides switching for the magnets. Unless I'm mistaken, the torque required to do so will be determined by friction in the rotor bearing (and some trivial air resistance) and eddy drag on the finger that is in the magnetic field (and, balanced out, attraction into the magnetic gap on entry and exit from the gap). The output torque on the flywheel will be determined by the magnetic field strength of the magnets (and some friction, da dah, da dah). Where am I falling down on my understanding? The rotor doesn't determine the output except in terms of how quickly it effects the magnetic switching. Or is there some other principle at work?

[swansont]

1 hour ago, Prajna said:

Turning the rotor merely provides switching for the magnets. Unless I'm mistaken, the torque required to do so will be determined by friction in the rotor bearing (and some trivial air resistance) and eddy drag on the finger that is in the magnetic field (and, balanced out, attraction into the magnetic gap on entry and exit from the gap). The output torque on the flywheel will be determined by the magnetic field strength of the magnets (and some friction, da dah, da dah). Where am I falling down on my understanding? The rotor doesn't determine the output except in terms of how quickly it effects the magnetic switching. Or is there some other principle at work?

Magnetic forces don’t do work. 
 

If you built this, you would see that it doesn’t run on its own. If you stop cranking, it will cease motion.

[Prajna]

5 minutes ago, swansont said:

Magnetic forces don’t do work. 
 

If you built this, you would see that it doesn’t run on its own. If you stop cranking, it will cease motion.

Absolutely it will stop with no input, I expect nothing else. If I hold a magnet above a ferromagnetic object the object (if it's not too heavy) will be attracted to the magnet. That has increased the potential energy in the object, so work has been done, has it not?

[swansont]

17 minutes ago, Prajna said:

Absolutely it will stop with no input, I expect nothing else.

So the input is where the work is done.

17 minutes ago, Prajna said:

If I hold a magnet above a ferromagnetic object the object (if it's not too heavy) will be attracted to the magnet. That has increased the potential energy in the object, so work has been done, has it not?

And the work will be done by you in moving the magnet - it takes more effort to move a magnet in the presence of another than it does in free space. That’s you doing work, not the magnet. 

[KJW]

6 hours ago, exchemist said:

18 hours ago, KJW said:

The design to which I am referring was also a perpetual motion machine of the 2nd kind. It consisted of a large diameter pipe radiating thermal radiation at room temperature, this radiation being focused onto a smaller diameter pipe, the increased intensity resulting in an elevated temperature of the smaller diameter pipe. I could see nothing wrong with this design and was forced to conclude that it is impossible to focus radiation to an image that is brighter than the source. I raised this on a forum I regularly visited at the time, and my hypothesis was confirmed by another member.

I suppose that depends on what is meant by "brighter". In terms of radiation intensity, I'd have thought one could increase that beyond the intensity of the source, if it is an extended source. But clearly one can't change the frequency of the photons merely by focusing a beam, so the effective temperature (if is black body radiation) of the radiation can't be altered. in that way. Is that what you meant?

By "brighter", I mean "higher intensity". It should be noted that black body radiation is not just a frequency distribution but also an intensity, and that any radiation that deviates from black body radiation, either by frequency distribution or by intensity, is radiation that can do work. In the case of the perpetual motion machine, the ability to focus black body radiation from an object into a smaller space increases the intensity of the image so that it is no longer black body radiation and can do work.

If one wishes to capture the entire radiation output of a small spherical object as an image, one can place the object at the focus of an internally reflective prolate spheroid. The image forms at the other focus. But note that symmetry demands that the image is the same size as the object, and hence the same intensity. On the other hand, if one uses a magnifying glass to focus sunlight onto a piece of paper, the image is much smaller than the sun, but then one is capturing only a tiny proportion of the total output of the sun.

 

 

Edited April 16 by KJW

[TheVat]

When people see a magnet doing work it is actually (e.g. a salvage yard crane) electric forces in the electromagnet and motor that do work. Could one say that magnetic forces are used to redirect and apply those electric forces?  So you have to have an electric current for the magnetic forces to be instrumental in doing work.

Sort of like a smooth ramp that is redirecting a lateral force (me pushing on a heavy appliance) to lift my appliance several feet upward.  The ramp does no work, it only redirects my force.  

[Prajna]

18 minutes ago, TheVat said:

When people see a magnet doing work it is actually (e.g. a salvage yard crane) electric forces in the electromagnet and motor that do work. Could one say that magnetic forces are used to redirect and apply those electric forces?  So you have to have an electric current for the magnetic forces to be instrumental in doing work.

Sort of like a smooth ramp that is redirecting a lateral force (me pushing on a heavy appliance) to lift my appliance several feet upward.  The ramp does no work, it only redirects my force.  

How does this relate to my response to @swansont above? Is it an attempt to answer that? My example refers to a permanent magnet rather than an electromagnet. It seems to me that the magnet is doing work rather than redirecting force. Or are you saying the magnet is redirecting the force I am using to hold the magnet up? What if the magnet is affixed to something?

24 minutes ago, KJW said:

By "brighter", I mean "higher intensity". It should be noted that black body radiation is not just a frequency distribution but also an intensity, and that any radiation that deviates from black body radiation, either by frequency distribution or by intensity, is radiation that can do work. In the case of the perpetual motion machine, the ability to focus black body radiation from an object into a smaller space increases the intensity of the image so that it is no longer black body radiation and can do work.

If one wishes to capture the entire radiation output of a small spherical object as an image, one can place the object at the focus of an internally reflective prolate spheroid. The image forms at the other focus. But note that symmetry demands that the image is the same size as the object, and hence the same intensity. On the other hand, if one uses a magnifying glass to focus sunlight onto a piece of paper, the image is much smaller than the sun, but then one is capturing only a tiny proportion of the total output of the sun.

 

 

Interesting but off topic, I believe, @KJW

Edited April 16 by Prajna
mistype

[swansont]

11 minutes ago, Prajna said:

How does this relate to my response to @swansont above? Is it an attempt to answer that? My example refers to a permanent magnet rather than an electromagnet. It seems to me that the magnet is doing work rather than redirecting force. Or are you saying the magnet is redirecting the force I am using to hold the magnet up? What if the magnet is affixed to something?

Magnets are another example of redirecting; magnetic forces are perpendicular to motion, so they do no work. 

[Prajna]

10 minutes ago, swansont said:

Magnets are another example of redirecting; magnetic forces are perpendicular to motion, so they do no work. 

That still doesn't compute here, @swansont, maybe it's just me being thick. The object is lifted, seemingly by the magnet, and thus its potential energy has increased and surely some work must have been done to achieve that, n'est-ce pas? What did the work? Surely you understand what I mean and I hope you are not being pedantic with regard to terms. In this example (to remove ambiguity, I'm referring to a permanent magnet fixed to some structure above the object, say a small sheet of metal).

[swansont]

8 minutes ago, Prajna said:

That still doesn't compute here, @swansont, maybe it's just me being thick. The object is lifted, seemingly by the magnet, and thus its potential energy has increased and surely some work must have been done to achieve that, n'est-ce pas? What did the work? Surely you understand what I mean and I hope you are not being pedantic with regard to terms. In this example (to remove ambiguity, I'm referring to a permanent magnet fixed to some structure above the object, say a small sheet of metal).

The work done is provided by whatever or whoever is holding the magnet. The magnet does not move into position where it can lift by itself.

[Prajna]

5 minutes ago, swansont said:

The work done is provided by whatever or whoever is holding the magnet. The magnet does not move into position where it can lift by itself.

Are you saying that in fixing the magnet to its support work was done but when the magnet lifts a small sheet of steel,say, that is placed under it that no work is done? Are you saying that the support is doing work? In placing the sheet under the magnet then work is done, no problem with that, but that work, unless the sheet is lifted into position, has not increased the potential energy of the sheet, whereas when the magnet lifts the sheet the potential energy in the sheet has increased. What caused that increase in potential energy?

[swansont]

2 hours ago, Prajna said:

Are you saying that in fixing the magnet to its support work was done but when the magnet lifts a small sheet of steel,say, that is placed under it that no work is done? Are you saying that the support is doing work? In placing the sheet under the magnet then work is done, no problem with that, but that work, unless the sheet is lifted into position, has not increased the potential energy of the sheet, whereas when the magnet lifts the sheet the potential energy in the sheet has increased. What caused that increase in potential energy?

I’m saying you aren’t looking very closely at what happens. A magnet does not magically move into place to lift something, and when it is moved, work must be done in doing so, and during the lifting process. By the system or person moving the magnet.

The magnet is an agent of transferring the force you are exerting, but the work done is by you, not the magnet.

[Prajna]

26 minutes ago, swansont said:

I’m saying you aren’t looking very closely at what happens. A magnet does not magically move into place to lift something, and when it is moved, work must be done in doing so, and during the lifting process. By the system or person moving the magnet.

The magnet is an agent of transferring the force you are exerting, but the work done is by you, not the magnet.

Ok, so it takes some work to lift and fix the magnet into place. But that has nothing to do with what I asked: what is lifting the sheet of steel I slide into position under the magnet? I don't lift it. Sliding it horizontally into position under the (fixed) magnet is a little work but it adds no potential energy to the sheet of steel. The magnet lifts the steel from its position below the magnet by magnetic attraction,which you insist is not work. The potential energy in the steel has increased since it has been lifted against gravity by the magnet; not by me, not by the (rigid and fixed) support but by the magnet. Something somewhere did some work and it wasn't anything but the magnet! When I slide another sheet of steel under the magnet (it's raised above where the sheets are slid under it, doesn't move, is fixed in place, so I really have to spell all this out?) You are speaking as if someone or something is lifting the magnet. In this example assume the magnet is fixed in place 30mm, say, above a table. I have a handful of small steel sheets on the table top, not directly under the magnet. I slide a sheet under the magnet, a horizontal move, and let go. What happens? Well in my world the sheet is attracted to the magnet and physically lifted off the table by the force of the magnet so that it sticks to the magnet. Say it was an electromagnet rather than a permanent magnet (didn't want to bring in electromagnets and let you guys complicate things further but necessary now in the explanation) and at this point in the experiment the electromagnet is switched off. What happens? In my world the sheet drops back to the table, its acquired potential energy converting to kinetic energy in the process. If you think the magnet did no work in that situation then I need a better explanation of how that can be since anything else adding potential energy to a system is doing work. Or am I wrong?

[swansont]

59 minutes ago, Prajna said:

Ok, so it takes some work to lift and fix the magnet into place. But that has nothing to do with what I asked: what is lifting the sheet of steel I slide into position under the magnet? I don't lift it. Sliding it horizontally into position under the (fixed) magnet is a little work but it adds no potential energy to the sheet of steel. The magnet lifts the steel from its position below the magnet by magnetic attraction,which you insist is not work.

Is the magnet hovering in space? I don’t think that’s happening.

(Further, what happens in the metal? You get an eddy current. The force doing work there is electric, not magnetic.)

The work - the energy input - is not the magnet. It’s something else. Magnets don’t get energy depleted by being used. They are not the source of the change in energy of the system.

[Prajna]

12 hours ago, exchemist said:

I had not heard of Ed Leedskalnin (not Leedskillin), but I see he was a Latvian immigrant to the USA who was active in  magnetism between the wars. I also see that indeed he was on the right track in interpreting magnetism as arising from circulation of charges within the substance, just as I described to you in my previous post. His understanding was thus a foreshadowing of what we understand today about magnetism from atomic theory, quantum physics and quantum chemistry. (Quantum theory was developed in the late 1920s and 1930s, possibly a little later than when he was writing about magnetism.) 

P.S. Curious fact: magnetism can in fact be shown to arise as a consequence of applying the theory of special relativity to electric charges in relative motion. I think that is rather cool. 

Ah, I hadn't seen this, perhaps it was edited in after I read your post. Thanks for the correction on Ed's name, I should really have looked it up. Yes, fascinating guy. He did some seemingly miraculous things and free-energy-cranks have been arguing over his book(s) for years, suggesting they were written in cipher, maybe they were. I rather thought that if anyone would be considered a crank then Ed would be right up there. Nice to be disabused regarding that.

Your curious fact is indeed curious, or certainly interesting. Whether I have enough interest to wade deep into relativity and QM to see it is another matter. If you can point me to general info about it that doesn't involve glazing over with esoteric formulae then I would certainly like to read it.

10 minutes ago, swansont said:

Is the magnet hovering in space? I don’t think that’s happening.

Further, what happens in the metal? You get an eddy current. The force doing work there is electric, not magnetic.

I explained exactly that the magnet is fixed. Maybe it's been there for years. Did I suggest, insinuate or even hint that it's floating? Eddy currents? What does that have to do with my question? I want to know what, in the circumstances I described, causes the increase in the potential energy in the steel sheet that is attracted to a magnet positioned above it. Just that. Answer that. Simply and clearly and without diversion, obfuscation or irrelevance. Can you do that?

[Ken Fabian]

I once tried building a "perpetual motion" machine not too dissimilar - not because I thought it would work but to work out what I was missing, to understand why it wouldn't. Needless to say it didn't work and I saw the push of magnets equaled the pull, with friction as well.
 

[swansont]

51 minutes ago, Prajna said:

I explained exactly that the magnet is fixed. Maybe it's been there for years. Did I suggest, insinuate or even hint that it's floating?

Do you understand that “fixed” is only an approximation? There is no such thing as a perfectly rigid structure. Which means that the mechanical structure flexes. There are mechanical forces, and they act through a displacement, i.e. they do work.

 

51 minutes ago, Prajna said:

Eddy currents? What does that have to do with my question?

Because that’s involved in magnetic attraction.

51 minutes ago, Prajna said:

I want to know what, in the circumstances I described, causes the increase in the potential energy in the steel sheet that is attracted to a magnet positioned above it. Just that. Answer that. Simply and clearly and without diversion, obfuscation or irrelevance. Can you do that?

You have to understand a bit of physics to appreciate the answer. If you don’t, then the answers might look like obfuscation or irrelevance. But you have an obligation here, because demanding an answer that involves a couple of semesters worth of physics, without having that knowledge, isn’t reasonable.