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Homework Help: Describe Charge Distribution on Spheres After They Touch

  1. Feb 4, 2007 #1
    I am trying to correctly understand the following problem:

    Here is the setup:
    I have two conducting spherical shells. We will call them S-Left and S-Right. Both spherical shells are initially grounded, therefore, they have no net charge w.r.t. Earth. S-Right is hanging from a string. S-Left is brought near a strong negatively charged object for a few seconds and then moved away. The side of S-Left that was brought near the negatively charged object is then slowly brought near S-Right until they both touch.

    1. Describe the motion of S-Right as S-Left approaches.

    My summary: S-Left still has no net charge but it does have charge separation due to induction. S-Left will have more positive charge on the side that is approaching S-Right. Since S-Right has no net charge and no charge separation, it will be attracted towards S-Left since electrons will move toward the side facing the approaching S-Left. The electrons will move towards the side nearest S-Left because S-Right feels the effects from the positive charges on S-Left more than the negative charges on S-Left due to negative charges being farther away on the other side of S-Left sphere.

    2. Describe the motion of S-Right after the two spheres touch and S-Left is held in place.

    My summary: I'm not sure. Neither spheres have a net charge but S-Left has charge separation. Do the electrons in both spheres evenly distribute between both spheres and remove the induced charge on S-Left? If this happened then both spheres will simply stay in the position at which they touched. Correct?

    Is my answer for 1. correct?
  2. jcsd
  3. Feb 4, 2007 #2


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  4. Feb 4, 2007 #3
    Would S-Left not have any charge separation?

    S-Left would have to have some separation of charge when it is near the large negative charge - correct? Am I incorrect in assuming that the charge separation stays on S-Left when it is moved away from the large negative charge?
  5. Feb 4, 2007 #4


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    The charges in a conductor are mobile. They won't maintain any separation w/o an external field.
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