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Earth as a giant sphere of electric charge

  1. Aug 12, 2010 #1
    I'm not a science student. So, I humbly request you to limit yourself to the basics, please do not indulge in infighting. If you ignore the request, you would be investing your efforts at the wrong place and perhaps it would be considered a pretentious show of knowledge.

    If a gold leaf electroscope is connected to earth, there is no deflection, earth is a neutral object. Then, how come whenever any charged object or electricity connection comes in contact with it, it absorbs all of the charge to neutralize the charge?

    Please help me with it. Thanks.
     
  2. jcsd
  3. Aug 12, 2010 #2

    mathman

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    Science Advisor

    The earth is very big. Charge from charged object to earth has essentially no effect on the charge density of the earth, while reducing the charge density to zero of the object in question.
     
  4. Aug 12, 2010 #3

    jtbell

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    Staff: Mentor

    This would not happen if the other (charged) object were as large as the earth. In this case (making suitable symmetry assumptions), if it were brought in contact with the earth, only half of its charge would migrate to the earth. The earth and the object would both end up "half charged."
     
  5. Aug 12, 2010 #4
    Thanks, Mathman.

    Then, it should carry an opposite charge in order to absorb the charge of other polarity, but how can it because it is considered a neutral body? It can absorb both kinds of charge. I don't understand it. Perhaps, some example could be helpful.

    Please remember I'm not a science student. Thanks.
     
  6. Aug 12, 2010 #5
    I'm not a physicist, yet.
    However, have you ever considered that perhaps the Earth is not neutrally charged? If the exact composition of the Earth is taken into consideration (By composition i mean, the X/100 of separate elements) and the sum charge associated with each X/100 (be they negative or positive), then it may be that the cumulative charge is different than neutrality.

    It would make sense then that the greater negative charge of Earth would absorb any lesser positive charge of an object whose charge was not equivalent to Earths negative charge.

    I like to look at it as magnets, just considering the strength of the north and south poles attraction. IF the poles had similar strength, then when their opposite poles were aligned, they would automatically neutralize the other. If one of the magnets had greater strength at its poles than the other magnet, then the weaker magnet would automatically be neutralized when it came into contact with the larger magnet. However, the charge of the greater magnet would not lessen or increase.

    Just a guess, I may be incorrect.
     
    Last edited: Aug 12, 2010
  7. Aug 12, 2010 #6

    jtbell

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    Staff: Mentor

    The earth doesn't need to be (say) positively charged in order to receive negative charge from a negatively charged object in contact with it.

    The negative charges on the other object already repel each other. Before you put the object in contact with the earth, they don't have any place else to go, so they stay on the other object. Put the other object in contact with the earth, and they do have someplace to go. The negative charges that move from the object to the earth, do so because they are repelled by the negative charge that stays behind on the object.
     
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