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Magnet is (kind-of) incredible

  1. Jun 23, 2005 #1
    Electrons inside of a solid matter spinning around their respective nuclei, with their axes quite parallel with the axis of that object, and that's how a magnet constantly supplies magnetic field (nice!).

    NOW: If I say that the magnetic field from a natural magnet is a mean of constant flux of energy, make a mechanism that successfuly converts that energy into mechanic energy, and if I say that such case wouldn't be in violation of the first law of thermodynamics (conservation of energy), where am I wrong (having in mind that the energy for magnetic field is provided from the force (what ever it may be) which is spinning the electrons)??
  2. jcsd
  3. Jun 23, 2005 #2
    Electrons spinning around nuclei? DO we need to go into on how many levels that is wrong?
  4. Jun 23, 2005 #3

    You cannot say this, because magnets do not put out energy. The magnet puts out force, but that force cannot do work.

    Do you think the earth is constantly expending energy to keep you on the ground? Its not. The only time you exchange energy with the earth is when you jump up and down.

    The only time you exchange energy with a natural magnet is...never, because magnetic forces cannot do work!
  5. Jun 25, 2005 #4
    ...But, that's not the point of my question.
  6. Jun 25, 2005 #5


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    You asked where you were wrong and Crosson showed you one place. Your argument fails because of this.
  7. Jun 25, 2005 #6
    Not true.

    There cannot be such a mechanism, because magnetic fields cannot do work.

    Suppose you could extract energy from the magnet. Then, without violating the first law, the energy you gained would be equal to the energy the magnet loses. The magnet would get weaker and weaker, and eventually stop supplying power when you extracted all its energy.

    There are two points about which you are most wrong:

    1) You think we can extract energy from magnets, this will never be possible.

    2) You think that even if we could extract energy from a magnet, that this would not diminsish the magnetic field. This violates the first law.
  8. Jun 27, 2005 #7
    But, electrons are always moving around the nucleus - what drives them? Even when you freeze the atom at -273 C degrees, electrons still spin (in most cases randomly, but in the case of natural magnet, there is some relative order).

    Magnetic field around the natural magnet is constantly provided - it goes and it goes, and it goes on. With the solenoid you must run the elctricity thorough the conducting wire - you yourself must provide some energy to it in order for it to work - so: obviously some sort of energy is provided to the magnet naturaly - you don't have to do a thing; for exactly the same effect and product you had to input something - here you get it for free; it goes on completely by itself - and it goes to waste.

    OK, those remarks about the fact that it is not an energy, but a force; but only in the last reply you touched the essence of the question I've made. You said that (IF it could be possible (hypotetically)) exploiting the force from the natural magnet would deplete it (in some way), but it works on it's own, you can't say that it does nothing - something happens there (obviously), and in order for something to be happening some energy must be spent (my point: what does it matter wheither natural magnet just 'hamster-wheels' around or that work is put to something usefull?).

    There is not much philosophy concerning magnet: it repels - it atracts; you can feel the persistance of that force - you need to constantly put some energy into trying to join them when they are repeling (you can fuse magnets into one object - only then something else happens, but when they are two - it doesn't seem to mind anything - it just repels/atracts (it won't quit and suddenly decide to change polarity) - the coloser you get them the stronger the force).

    I have an analogy: imagine that you have one sealed room, and you have two cilinders with fans inside (lets put some particles in the room too - e.g. confetes - to see where and how the air moves); now - because the room is sealed the air can't escape, so it must circle (convection) - (which is just like the natural magnet); let's imagine that the air blows upwards, an then it rushes down only to me sucked in again. When you turn them both on you can see the interaction: if the cilinders are oriented in such a way that they blow toward eachother they will repel, and if you algn them to blow at the same direction they atract (and the (third) case I didn't explain... which may point to the nature of the magnetism itself in contrast to this analogy).
    Last edited: Jun 27, 2005
  9. Jun 27, 2005 #8
    The point of it all: it seems like magnet is defying the 'energy conservation law' - never mind you use the produced force or it just goes to waste (unnoticed or just noticed and nothing else).
  10. Jun 27, 2005 #9
    you are correct in saying that the field is due to the magnetic moment associated with the spinning electron. due to its spin, it behaves as a dipole. magnetic field does not do any work when the charge moves parallel to the magnetc field else it does...

    but what you are saying that you would convert the internal energy of the magnet is not easy and is almost impossible..its same as drawing energy from a revolving electron in an atom . however if its done the law of thermodynamics will not fail as only energy transformation takes place but remember such mechanism is impossible...you will need to provide much more energy than what you will recieve;input will be much much more than output to extract energy from a magnet....not a practical approach also....
    Last edited: Jun 27, 2005
  11. Jun 27, 2005 #10


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    It may seem like to you, but not to me. There are lots of examples where something "just goes and goes" with no input of energy: a spinning wheel, a coasting car, the moon going around the earth. In all of these there is eventually a running down because of friction, but in the microscopic world, there is no friction. Even a superconducting current loop will have the current racing around forever with no loss. Constant motion does NOT require constant input of energy. This was shown by Newton 400 years ago.
  12. Jun 27, 2005 #11
    Im only going to say this one more time: a constant magnetic field does not mean constant output of energy. (whether or not it can be harnessed).

    You seem to be imagining that a magnet is constantly shooting out energy in all directions and that is just not true. It might be better to think of the space around the magnet as a lumpy rubber sheet, and objects as rolling around on the rubber surface.

    The point is, magnetism is more like a lumpy rubber sheet: once you stretch a lump in it (which takes energy) then it doesn't matter how many things roll over the lump or get repeled by it (doesnt take additional energy to interact).

    This is a less sophisticated version of the idea that forces require exchanges in energy. I see it often enough, so maybe you can think about gravity (and why gravity doesnt defy conservation of energy):

    The earth-sun system violates the first law of thermo because the sun is constantly using energy to spin the earth. The suns gravity is a constant flux of energy and so it violates conservation of energy.
  13. Jun 27, 2005 #12
    well i didn't look only at your second post...i avoid reading long posts :smile:

    anyway it's not so that some energy needs to be provided continuously..an event started at -infinity will not stop unless some external force is there to cease it's motion as mentioned by the previous poster correctly....but yeah some sort of energy is surely associated with the system and it's this energy (say E)that you need to provide first to break the equillibrium condition of the electron -nucleus pair and after that only you can think of extracting energy from the revolving electron(practically impossible) and for that also you need to provide some additional energy...so E provided is a waste and hence its not practical...case of solenoid is different; it is not having the current flowing through it in equillibrium condition and you are the one to force the current but mechanism of atoms is totally different...it's the basic property of the atoms to have e-s revolving around the nucleus and the energy associated with such a system is the energy that was assumed to have been given at -infinity to start the event, which cannot cease unless acted upon by some external force and hence the e-goes on and on....
  14. Jun 27, 2005 #13

    Sazar, when the magnet is attracted to an object, it does work in the process.

    The potential energy in the magnet is changed into kinetic energy.
  15. Jun 27, 2005 #14

    It does not actually even make sense to say that there is, or is no friction in the microscopic world.
  16. Jun 27, 2005 #15
    I can't doubt (of course that's not the point) that preservation of energy rules everything, but - hypoteticaly - how do you see exploiting this would look in terms of conservation of energy - would electrons stop?
    Last edited: Jun 27, 2005
  17. Jun 27, 2005 #16
    The electrons in an atom can absorb photons (gain energy) and emit photons (lose energy), and therefore they can access many different energy levels.

    Finally, we have made some progress. What you are talking about is the ground state. This is the lowest energy state (electrons are as close to the nucleous as possible), and the surprise is that the lowest energy state is non-zero (they can't stop as you said).

    One of the classical paradoxes that cannot be resolved without quantum mechanics is the prediction that electrons are doomed to spiral in to the nucleous.(Classical Mechanics says that stable atoms cannot exist!)

    QM solves this problem by allowing us to calculate the (energy and "radius") of the ground state, the lowest state an electron can ever be in. The energy of the ground state of hydrogen is something like -13.6 electron-volts.

    So we take out energy untill we cannot take out anymore, and find that there is still 13.6 electron-volts of energy left in there that we cannot extract. No matter what happens, the electron cannot fall to a lower energy level.

    At this point you (and many others) propose the following scheme: Since the electron cannot fall to a lower energy level no matter what, you can suck infinite energy out of it without it falling to a lower level (without it stopping, you say).

    The problem: There is no way to extract energy from an electron in the ground state!

    So crackpots say: suppose there was a way to extract the energy from the ground state (suppose magnetic forces could do work), then wouldn't it be infinite energy?

    NO! If you some how could extract energy from the ground state, then it wouldn't be the ground state! In short, extracting energy from the ground state is a semantic paradox, a bunch of total nonsense.
  18. Jul 1, 2005 #17
    OK, but, regarduing macrophysics (not atoms and how it all looks inside):
    Can you explain the interpretation of a problem with perpetual motion including magnets (it sounds interesting, but I've never had an opportunity to expirience it)? - I guess the problem is with the opposite pole of the magnet, because the magnet "senses" it so it won't fall to the point where it is to be pushed away (instead it falls into equilibrium point?), but aren't there materials which insulate magnetic field (alloys with nickel (mu-matal)) - what's the problem with it? Can natural magnet be shaped in such a way that it concentrates its magnetism in order to avoid that problem?
  19. Jul 1, 2005 #18
    Oh, I think I get what you're saying. You're wondering what would happen if you were to move the repelling ends of two magnets together by putting a strongly diamagnetic (i.e., magnetic-field insulating) plate between the two. You're thinking that if you did this, and you then removed the plate, the magnets would repel again, giving you free energy, right? Unfortunately, nature has a way around this. You see, you have to give up energy to move the plate into the magnetic field. Materials which "insulate" magnetic fields do this by creating their own internal magnetic fields in the reverse direction of an applied field. Thus, moving the plate into that field requires that you realign the spins of the electrons of the plate, costing you energy.
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