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Homework Help: A positively charged elctroscope near a finger

  1. Apr 9, 2009 #1
    1. The problem statement, all variables and given/known data
    A positively charged electroscope (with deflected leaves, obviously) is approached by your finger (but not touched). Will the deflection increase, decrease, or remain the same?

    2. Relevant equations
    None, purely conceptual

    3. The attempt at a solution
    I think the effect would be very slight. The electroscope would polarize the mlcls in your finger, causing a net attraction. The neg. charges in your finger near the electroscope woud repel some electrons down into the leaves and partially neutralize the positive charges in the leaves. This will cause the deflection to decrease slightly.

    What my question really amounts to is:
    Does a dipole induced by a conductor, in turn, polarize the conductor even a little.

    Out of curiousity if the finger were replaced by a neutral conducting metal rod what would happen? I know the body is conductive, I'm just not exactly sure if the effect is the exact same in this case.

  2. jcsd
  3. Apr 10, 2009 #2
    Well really, you'd need to put your finger bang in the middle to see any effect at all, hmmm, i doubt it would amount to much really, and you're right, if anything the deflection would decrease, and the conductor would be very very partially polarized.

    And i think you're right, the effect would be alot more obvious with a neutral conducting metal rod, an interesting question though! I'm sure someone has seen it before :P
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