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What produce the earth magnetic fields ?

  1. Apr 27, 2006 #1
    I am wonder what produce the earth's magnetic field .Can anyone tell me . Besides , I am doing a experiment to measure the horizontal component of earth's magnetic field . I am using a copper (about 16 mm in length) and a power supply of two volt . I use the copper to create the solonoid but suprisingly the ammeter show that there is no current flow in the circuit . That means that the copper cannot conduct electricity . How it can be the copper cannot conduct eletricity since the wire is made of copper .
  2. jcsd
  3. Apr 27, 2006 #2
    The earth's magnetic field is caused by electric curents in the earth's core region. This core is metallic in nature.

    Check this out

  4. Apr 27, 2006 #3


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    The current state of understanding of this matter is very poor. The dynamo effect is the best guess, but still does not answer many questions (like the cause of the pole flips).

    As for your field measurement circuit...we can not tell you what is wrong unless you show a diagram/schematic of the circuit (in the advanced post page, there is an option to attach files) or give us a complete description.

    What principle are you using to measure the field ?
  5. Apr 28, 2006 #4


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    Naive question of course, but your solenoid is moving/rotating, right ?
    If it is static of course you won't see anything...
  6. Apr 28, 2006 #5
    I use the battery to connect to the solenoid so that it become a magnet ,not se the solenoid to generate electricity . But there is no current flow .I waonder why
  7. Apr 28, 2006 #6


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    I thought you said that you used a ".....power supply of two volt ..."?

    As Gokul said, without a complete description, who knows what is going on.

  8. Apr 28, 2006 #7


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    In other words, you shorted the battery, and now it is empty ? :blushing:
  9. Apr 28, 2006 #8


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    Sounds like it.

    peter : But that's only a guess. Unless you describe the circuit, no one will really know what happened.

    Use a voltmeter and check that your battery is still okay. Next time, use a series resistor of at least 20 ohms (for a 0.25W resistor). If you don't do this, you will draw a very large current from the battery. Most household batteries are not rated to deliver more than 1A.

    In any case, by making an electromagnet, how do you achieve the objective of measuring the horizontal component of the Earth's field ? Tell us the principle you are using to perform this measurement. Then tell use how you are building a device that uses this principle.

    Of course, if you feel lost, ask for help.
  10. Apr 30, 2006 #9
    wat i remember about earth sciences back in high school is that the earth's mantle or core is made up of molten iron and other magnetic material and becoz they are rotating around inside the earth, they generate a magnetic field

    correct me if im wrong...
  11. Apr 30, 2006 #10


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    I think it is the other way around, the magnetic field is making the core spin.
  12. Apr 30, 2006 #11
    I just happen to have a copy of the Scientific American to hand, just as well because this isn't my field at all! "Probing the Geodynamo". It would appear that the mantle revolves faster than the inner and outer core. The upwelling of hot buoyant parcels of liquid iron towards the mantle combined with the Coriolis effect give a rotational speed differential between the core and the mantle and hence the dynamo effect.
    Paul D
  13. Apr 30, 2006 #12


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    Thanks for that, Paul. Weird... I buy every issue of SA, and I don't remember seeing that.
    Ngk (no way am I going to type out your whole damn name); this might seem idiotically simplistic, but are you sure that there's no break in the continuity of your circuit? Could there perhaps be a defect in the connection into your VOM? That's happened to me a couple of times. If a meter gets beaten around a bit, the plug-ins sometimes don't conduct properly. I learned that the hard way after carrying mine around in the same tool pouch with a few sets of Vise-Grips and a dozen screwdrivers.
  14. May 9, 2006 #13
    That is really on my mind too.
    It seems like the most easy suspect is different rotation speeds, since that is what you find on the sun.
    But as far as I can see, many, not all planets, and some moons, have magnetic fields.
    http://gsc.nrcan.gc.ca/geomag/index_e.php [Broken]

    Still, layman to layman, it seems like you really have to have a magnet present to get the magnetic field from the rotation of the ores.
    Last edited by a moderator: May 2, 2017
  15. May 9, 2006 #14


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    That's why the magnetic field is making the core turn, and not the other way around. Am I right?
  16. May 10, 2006 #15
    "The theory of the process is very mathematical and intricate, because to produce the currents, you need not only a flow of liquid iron, you also need a magnetic field, and this field is none other, but the one created by the currents themselves!"

    Also, I think there are some problems with the aging of a magnetic field. Hope you got your experiment going again.
  17. May 10, 2006 #16


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    Considered by many to be the leader in the field;
    Still no diffinitive answer, but they are producing real datya in a laboratory model.
  18. May 11, 2006 #17
    Oh my gosh! It's a good thing they can do this experiment with those tubes and copper and sodium and refrigerator size magnets! That is better than crashing all those LARGE computers on the complexity of the problem! After all, this is taxpayer funded, via the NSF $6billion per year.
  19. May 11, 2006 #18


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    All you need to generate a magnetic field is a flow of current. Relative motion of the various depths will represent charge in relative motion, this is a current. Thus a electro-magnetic field will be generated.

    For the magnetic field to drive the core you must have a source of energy. The core is quite massive it would take tremendous forces to drive this mass of metal. What is your source of energy to do this?
  20. May 11, 2006 #19
    Relative motion differentiation, in itself, causes electron current flow? Since when?

    Show me an experiment that molten metal, spun at "layerd" differential speeds(such as in a blender-type apparatus) has produced a magnetic field.
    Last edited: May 11, 2006
  21. May 11, 2006 #20


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    That sounds like a challening experiment on any scale, and I doubt that it has been done on a large scale. It is concievable that small scale would give different results from large scale as it could be a matter of measurability.

    (Perhaps I need to spend some time looking at the above links.)
  22. May 11, 2006 #21
  23. May 12, 2006 #22

    Seriously, you should move closer to one, North or South Pole.

    Last edited: May 12, 2006
  24. May 13, 2006 #23
    I really don't know for sure.
    But I would think that magma movements inside the core of the planet has something to do with it.
    It definitely contains permeable elements like Iron and Nickel.
    IIRC,the most interesting enigma about it is a decrease of Earth magnetic field measured over centuries.
    I also remember reading somewhere they established that every 1000- 2000 centuries or so in history,poles of the "earth magnet" exchange their polarity (reverse signs).
    Also unknown why!
  25. May 13, 2006 #24

    The polar reversals are recorded on the ocean floor and all rocks that acquire the direction of the poles at the time they were formed. Paleomagnetic dating looks super fascinating and it would be fun to have a SQUID! Anyway, 1000-2000 centuries is not quite correct. What the scientists say is that they happen very sporadically, from several thousand to several million years between events. Then they say each reversal takes 5000 years. The poles wander quite a bit also.

    I personally struggle with the estimation that it happens so irregularly. If you look at the stripes on the ocean floor, they are pretty even. I need to find some pictures of the magnetec anomalies that are a lot further away from the mid-ocean ridges, just to be sure. Also, the sun reverses polarity every 11 years. I wish I could find more about reversals on other planets, and moons--maybe someone has more info.

    Also, you mentioned that the magnetic field has weakened, and it has over the last century, by as much as 10% some studies say. I try to use reputable sites for my info. The weakening may very well mean we are due for a polar reversal.
  26. May 13, 2006 #25
    100,000-200,000 years were figures from my memory Paula.
    Maybe that's was an estimated mean of the average period of the reversals?I don't know becouse it was long ago I heard/read about it..

    Yup,we are likely to be close to yet another reversal I agree.
    The "end" of World is coming !
    :cry: :uhh: :yuck: :devil: :wink:
    Last edited: May 13, 2006
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