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Free unlimited electricity in space?

  1. Jun 26, 2011 #1
    Free unlimited electricity in space??

    A Changing Magnetic Field Produces Electricity. Suppose we build a huge coil in space and place a strong magnet in between.We then provide an external spin to the magnet.In space,there is no opposing force.thus,according newton's first law,the magnet will keep spinning and we can harness electricity for as long as we want.
    wouldn't that solve all the energy problems on earth??
  2. jcsd
  3. Jun 26, 2011 #2


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    Re: Free unlimited electricity in space??

    Moving a magnet past a wire will induce a current in the wire. Ultimately this is how you will "harness" the electricity.

    However, electricity moving through a wire produces an that opposing magnetic field. i.e. your freely-spinning magnet will experience a resistance and will rapidly slow down.

    What you have there is a battery, storing angular momentum, that you can convert into electricity until it stops spinning.
    Last edited: Jun 26, 2011
  4. Jun 26, 2011 #3
    Re: Free unlimited electricity in space??

    thanks a lot sir!
    but this means that if keep giving the magnet additional spin by some external device,then we can store the angular momentum to store huge amounts of energy in a battery.this can in turn be used to power,say,space stations, right??
  5. Jun 26, 2011 #4


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    Re: Free unlimited electricity in space??

    It will take energy to spin up the magnet. In point of fact, it will take more energy to spin up the magnet than the amount of energy you will get out of it (because all real systems have some loss due to friction and heat).

    So you haven't actually made a source of energy.

    Again, think of a battery, like a 9V rechargeable battery. You can power a device (like a cooling fan) from a battery for as long as the battery lasts. But if you want to keep your battery topped up, you need to have it hooked up to a recharger.

    But look what you've got - your fan is now simply powered by whatever is powering the recharger - the battery is an extraneous part of the circuit. You could remove it.

    Your magnet spinning in space needs a source of energy to keep it going. But as soon as you introduce that source of energy, you can simply power Earth from that source, and get rid of the magnet, which is not accomplishing anything.
  6. Jun 27, 2011 #5
    Re: Free unlimited electricity in space??

    But Sir, what if you provide an initial torque to the magnet,wait for it to stop spinning,and then again provide torque and repeat the process?? I know that an external source is required to do this.But can this,in any way,increase the output to input ratio[you don't need to keep providing energy,just do it when the spin stops]?Or will it be the same?
  7. Jun 27, 2011 #6
    Re: Free unlimited electricity in space??

    The conservation of mass-energy says you can't create energy out of nothing. No matter how you rig up magnets and wires or when and how you spin up the device, it will always take more total energy externally applied to spin the device than you can get out of it in the form of electricity.
  8. Jun 27, 2011 #7


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    Re: Free unlimited electricity in space??

    You are succumbing the classic perpetual motion tweaking-to-infinity folly. The assumption that adding one more bit of complexity will cause it to get more efficient. No, each addition of complexity causes it to get less efficient.

    Regardless, it will never be more efficient than 1. i.e. you will never get more energy out of it than you put in.

    If it takes 1 million Joules to get it up to speed, the best you can hope for (even in a perfect computer simulation) is 1 million Joules output. If you keep adding torque every time it slows down (say, another .5 million Joules) then you will get another .5 million Joules out of it.

    Your device is not making any energy; it is only converting input energy to stored angular momentum, then converting it back. It's a zero sum.
  9. Jun 27, 2011 #8


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    Re: Free unlimited electricity in space??

    And fyi, the limitations in space are almost exactly the same as those on earth. Being in space does essentially nothing for you:
    1. Being in space doesn't offer much less friction than being on earth.
    2. Friction isn't a large component of lost power anyway: most generators are over 95% efficient.
  10. Jun 28, 2011 #9
    Re: Free unlimited electricity in space??

    Thank you very much!That was really helpful!
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