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Where does energy come from?

  1. Jun 26, 2006 #1
    Ok, from the big bang, to the Stars, as radiation to the plants, eaten by animals that I just had for supper...no really.

    Everything has electrons. Magnets are always surrounded by a field. Use the M field to induce current into a wire, now you have E and M fields. We can use electricity to generate a magnetic field. We can use a magnet to generate electricity. We can even use an elctomagnet to do the same. Something is missing. Where does the original fields draw energy from?

    Think about it. I don't want the easy textbook answer. It's always, it's just already there...come on. No it's not.

    You can't tell me that if I wake up one morning and start moving a magnet over a wire, it will make electricity indefinitely, with no deterioration of the magnet. That would mean that the magnet has an infinite field stregnth. Not likely.

    So really, where does it come from?
  2. jcsd
  3. Jun 26, 2006 #2
    Quoted from Wikipedia
    "In quantum physics, the photon (from Greek φως, "phōs", meaning light) is the quantum of the electromagnetic field (light). That is to say, electromagnetic fields are made up of large numbers of photons, and the electromagnetic interaction is mediated by the exchange of virtual photons."
  4. Jun 26, 2006 #3
    When you generate electricity with magnet and wire the energy comes from whatever is moving the magnet, not the magnetic field. The special property of the magnetic field is that it can interact with the electrons in the wire, pushing them, so to speak, in one direction or the other. The energy comes from your hand and arm moving the magnet, or from the engine, whatever kind it may be, that moves the magnet. If the magnet's moved by wind power, or water, then the energy is coming from the wind or water. You aren't harvesting any energy from the magnet or it's field.
  5. Jun 26, 2006 #4
    Which textbooks gives that answer?
    zoobyshoe gave you the textbook explanation, the correct explanation.
  6. Jun 26, 2006 #5
    I don't think the original posters' question has been addressed. I think he confused the issue by mixing in magnetism. Do you think maybe the following was his question?:

    "I have an electron in one hand. I pick up another electron and move it towards the first and then let go. That electron will fly away. I do this again. Another electon flies away. I can do this repeatedly for a thousand years, and the original electon never seems to wear out! It seems to be an inexhaustible source of energy..."
  7. Jun 26, 2006 #6
    To add something: Magnets DO have a "lifespan".
    The following qoute is from http://www.magnadrive.com/faq/faq-magnets.shtml [Broken] and is in respect to neodymium(rare-earth) magnets.

    Q: How long will the magnets last?
    A: The half-life of the magnets is 2,000 years.
    Last edited by a moderator: May 2, 2017
  8. Jun 26, 2006 #7
    This is closer to the answer that I was looking for. Thank you.

    Take an atom of hydrogen, the electron spins around it forever as far as we know. Why can it do this? Shouldn't it slow down eventually? Or fly away? Will the proton always pull equally to keep it in place? If so, how? In any other sense of the word, an atom is an engine. It does work. Not really useful most of the time, but... So, it is an engine that is always running. Any system that does work requires energy to be input. Does not this hold true for an atom? If so, then where does it come from? (yes they are held together by electrostatic force...but, where does the force originate?)

    I'm sorry to be so naeive, I am just uneducated, but I am trying. Some questions just are not answered anywhere. I was more than a little vague intentionally. I wanted a wider response pool. I thank those that took the time to answer.
    Last edited: Jun 26, 2006
  9. Jun 26, 2006 #8


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    Actually, Zoobyshoe is correct. A moving magnet produces a time varying magnetic field in a conductor which induces charges to move, and moving charges a current make (assuming there is some net motion).

    Some mechanical energy (by virtue of force through some displacment) must be expended to move the magnet.

    In a bound state, with no change in potential energy, the atom does no work, or rather there is no work on the electron. QM explains why the electron does not slow down, or fly away, but the electron 'remains in orbit', unless an external influence acts upon the electron. The external influence could be a photon, another electron, or some charge particle.
  10. Jun 26, 2006 #9
    You would have heard of Newton's first law of motion.
    If a body is moving, it will keep on moving in its state until a and unless a force on it.
    Now, if a body is moving and there is no force on it, it will continue to move forever. What provides the energy?
    (I know that it is not answer to your question, it is just an extension)

    Keep Smiling
  11. Jun 27, 2006 #10
    For my part, after thinking on it for a while, I just said "an electron is an inexhaustible source of repulsive force" and moved on. It's not a trivial question, I just don't think there is an answer.
  12. Jun 27, 2006 #11


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    In our macroscopic world, we take friction and energy loss as a given. We assume that someting in motion will eventually stop unless more work is put into it.

    This is NOT the general case in the universe. The general case in the universe is that things in motion stay in motion. And on the atomic/subatomic scale, there is no loss due to friction or heat or whatever.

    It would help to recognize that, even in our macroscopic world, these losses due to heat or friction or whatever aren't really lost, it's just that the energy is converted (not lost!) into forms that are of no use to us (i.e. not recoverable).
    Last edited: Jun 27, 2006
  13. Jun 27, 2006 #12
    As to this question, zoobyshoe answer is correct regarding this situation as well. Here the energy is added to the system when you move the electron closer to the other electron. Once you let go of one of them then the potential energy of the electron given to it by moving it closer is released as kinetic energy.
    Remember charge is conserved as well as energy. So if the electron was losing its charge then it would be breaking the laws of physics.
  14. Jun 27, 2006 #13
    Thank you all. This is the best answer that fits the question I was trying to ask, but did not know how.
    So the rules are different on the atomic scale. Interesting. It is the losses in the macroscopic world that I was trying to understand -why they don't apply to the atomic scale. The closer I get to the answers the further away the goal gets.
    Just as a wild example though, if you put a generator motor into a high state of spin in orbit (vaccum, zero g) and shielded it from radiation, etc. would it spin indefinitely?(fictionally assume friction is eliminated somehow)?
  15. Jun 27, 2006 #14

    So, if fluctuations in the magnetic field are caused by motion, then can we make gamma radiation if we, for example shake a magnet fast enough?
  16. Jun 27, 2006 #15
    Allow me to make an analogy:

    Lets say magnetic fields are a broom, the metal is represent by the floor, and electrons are bits of dirt on the floor. You push the broom along the floor, moving the dirt around. The system is composed of four things: You, the floor, the dirt, and the broom. Which is doing the work? Does it make sense to say "the broom has infinite energy, because it can push the dirt around for eternity"?

    That's what magnetic fields are. They are the "broom" in these interactions, a way of converting effort from one form to another.
  17. Jun 27, 2006 #16
    So, where does energy come from?
  18. Jun 27, 2006 #17


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    Asking this question is like asking where mass comes from. Energy is a property of the universe, as is mass. All mass and energy originated in the big bang. The energy that exists today originally appeared in the big bang. There has been no energy added to or taken away from the universe since then.
  19. Jun 27, 2006 #18
    What about symmetry breaking?
  20. Jul 8, 2006 #19
    Totally wrong actually, you're forgetting the blue screen sink factor.

    After an hour two of dealing with the blue screen you'll feel tired and yet have achieved zero gain.
  21. Jul 9, 2006 #20
    There is energy stored in E&M fields.

    Energy is a construct. It allows us to predict things, but it isn't like you can hold it and say "ahh so this is what energy is".
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