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Need Help to understand the answer.

  1. Oct 6, 2012 #1
    Three objects are brought close to each other, two at a
    time. When objects A and B are brought together, they attract. When objects B and C
    are brought together, they repel. From this, we conclude that (a) objects A and C
    possess charges of the same sign. (b) objects A and C possess charges of opposite sign.
    (c) all three of the objects possess charges of the same sign. (d) one of the objects is
    neutral. (e) we need to perform additional experiments to determine information
    about the charges on the objects.


    The answer is: (e). In the first experiment, objects A and B may have
    charges with opposite signs, or one of the objects may be
    neutral. The second experiment shows that B and C have
    charges with the same signs, so that B must be charged.
    But we still do not know if A is charged or neutral.




    I am not understanding the part that neutral objects are attracted to charged objects.
    If they one is neutral and the other is positively or negatively charged then how can they attract each other.

    I do not know if this attraction is related to gravitational force..
     
  2. jcsd
  3. Oct 6, 2012 #2
    Both neutral and charged objects have many positively as well as negatively charged particles. In neutral objects the number of the positively charged particles equals the number of negatively charged particles so there is no net charge whereas in a charged object either the number of positively charged particles or the number of negatively charged particles is more to correspond for the net charge.... so now when a charged object is kept near a neutral object an equal and opposite charge is developed on the surface of neutral object that is near to the charged object and this happens because of induction and hence due to the development of these charges the neutral object is attracted towards the charged object.....
     
  4. Oct 6, 2012 #3
    The attraction of a neutral object by a charged one is due to polarization of the neutral.
    The neutral object contains charges of bot kinds (negative electrons and positive protons).
    The electric field of the charged object will induce a change (even so small) is the distribution of these charges. The nature of the actual effect depends on the nature of the neutral object (insulator, conductor) but the effect is that the side of the neutral which is closest to the charged object will have an overall charge of the opposite sign.
     
  5. Oct 6, 2012 #4
    Hum ok.

    So the induction provokes a overall charge of the opposite sign in the neutral's side that is closest to the charge object. And therefore the attraction.
     
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