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Harness energy of Earth magnetic field?

  1. Jan 30, 2013 #1
    Somebody estimated that if cables will be extended from pole to pole and contacts placed on equator we could obtain 100.000 V, as Earth rotates in its own magnetic field.
     
  2. jcsd
  3. Jan 30, 2013 #2

    Drakkith

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    Ok. Did you have a question?
     
  4. Jan 30, 2013 #3
    Is it true or not?
     
  5. Jan 31, 2013 #4

    sophiecentaur

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    Who is "somebody" and do you have a reference?
     
  6. Jan 31, 2013 #5

    russ_watters

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    Voltage isn't energy.
     
  7. Jan 31, 2013 #6

    jim hardy

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    Question more.

    Heard of any such effects on N-S railroad tracks, like Miami to Quebec?
    Or power lines?

    Ocean water is a conductor and very nearly spans the poles.

    Crackpottery is easy to test.
     
  8. Jan 31, 2013 #7

    sophiecentaur

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    The only possibility would have to involve a ring round a meridian N-S-N. That would produce the Faraday Paradox Induction Effect. There isn't enough Area involved with any other loop moving through the Earth's field. Perhaps someone could calculate the emf and then the possible power output for us???
     
  9. Jan 31, 2013 #8
    The thing that people forget when dreaming about electricity from earth's magnetic field is that the field is stationary looking to it in overall , ofcourse it changes a little and drifts but the changes are so little that on a large scale it just wont do , as to induce current in a wire you either need a time varying magnetic field or you have to move the coil, just putting a coil in a stationary field won't do.
    So you would need a bearing type cable around earth and you would need to spin it and then you would get current induced , the problem again is spinning something requires energy, so in the end reality is harsh.
    @sophiecentaur again writes faster than me:D

    I guess I got the idea about the faraday paradox you mentioned , the whole system would then function as a simple homopolar engine, like a single wire from a AA battery + to the minus terminal?
    The problem Is earth itselft isn't a battery which gives voltage at certain terminals nor a magnet in a way that soil would conduct so I have a little bit of problem understanding your paradox case scenario.?
     
    Last edited: Jan 31, 2013
  10. Jan 31, 2013 #9

    sophiecentaur

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    The Faraday paradox involves generating an emf even when magnet and loop are rotating together. Isn't that what would happen with a loop around the Earth n-s-n?
     
  11. Jan 31, 2013 #10
    I guess so but doesn't the ends of the wire have to be connected to the magnet so that current could flow.Otherwise it would be like spinning a magnet and wire around it both at the same rpm but not physically connected and that wouldn't induce current in the wire as there would be no closed path for the electrons to move.And the field seen by the moving coil would be static just like you would place a magnet next to a wire sitting on a table.
    So I understand that they have to be connected physically then the question is earth as we know are not all made of magnetic minerals and ore , how does one connect the N-S-N wire to the ground for the electrons to flow?
    Dig until reach mantle but that would melt the cable and again no luck.
     
  12. Feb 2, 2013 #11
    @sophiecentaur so how it is actually , could you please see my last post, as I believe this thread just got forgotten a little bit, but not 100% finished.
    :)
     
  13. Feb 2, 2013 #12

    sophiecentaur

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    Sorry. Mind elsewhere.
    The magnet doesn't need to be part of the circuit - why did you think that was necessary? Was it because of some of the demos on YouTube? All you need is a loop or loops of wire and a changing magnetic flux. Some magnets are not even of conductive material but can be used in generators.
    Actually, I was trying to think up a suitable geometry for the loop of wire and I found that most feasible layouts seem to involve induced voltages almost cancelling out. The problem is that the Earth's field is very weak and needs a massive loop area to obtain any more than a 'just detectable' amount of power.
     
  14. Feb 2, 2013 #13
    Well I thought of it as the Faraday disc,in his case the rotating magnet was electrically connected to the wire via rolling brushes or other mechanism.
    But If you don't do that I think the current induced in the wire will be even less than in the wire to earth scenario as basically the earth spins and the wire does that together with earth and the earth magnetic field speaking generally doesn't change that much at all as much as I know. Basically the wire would see pretty much static magnetic field am i right? Hence very small almoust laughable current would be induced?
     
  15. Feb 2, 2013 #14

    sophiecentaur

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    IFFF you could drop a wire down through the Earth, to connect north and south poles, and then ran a semicircular wire on the surface, the rotation of that loop, once a day, would generate a significant emf. The Faraday paradox is explained by the fact that the earth's magnet, spinning on its axis produces a stationary field - not an intuitive thing at all and hard to cope with (for me, anyway - I just have to accept it). Those demos on YouTube show this happening.
     
  16. Feb 3, 2013 #15
    Ok now I understand more what you meant.yes I have seen them too, at the first moment i double checked the information as I don't have much trust in all those "random guy in a garage" videos on youtube but yes this seems to be so.
    I think the important part here is that you have to have one wire a loop around earth N-S-N and then another one straight through earth and then connect the loop with the straight one via some brushes or so and in between a capacitor, now that reminds me the Farday thing quite clearly yes.
    I think the problem arises about when one would want to put the straight wire through earth. :D
     
  17. Feb 3, 2013 #16

    sophiecentaur

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    You woulds see those demos in School too (I did when I was a lad) but Health and Safety forbids the use of mercury! So far, they can't control what you do in your garage (at least what you do with mercury).
     
  18. Feb 3, 2013 #17
    hi, friends, i have heard about something called as electrodynamic tethers. These are long conducting wires usually of aluminium which are used to change the orbits of spacecrafts. I took this subject for my class seminar. These electrodynamic tethers actually uses earth magnetic field. They have also been used to produce higher electric current for experiments.
     
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