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Homework Help: Intro electric field question

  1. Jun 25, 2006 #1
    I am just reviewing some E&M because i took the class before I ever thought i had that big of an interest in physics and just memorized formulas, etc. Anyway, this is from a "which of the following statements is true" question.

    The true statement is: A positive charge experiences an attractive electrostatic force near a neutral conductor.

    The alternatives were that it experiences a repulsive force, no force, ...

    How come the true statement is indeed true as opposed to a positive charge experiencing no electrostatic force near a neutral conductor?
  2. jcsd
  3. Jun 26, 2006 #2
    Charge redistributes itself on the surface of the conductor in response to the presence of the charge. Negative charges are brought close to the positive charge, resulting in a net attraction.
  4. Jun 26, 2006 #3


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    Staff: Mentor

    Is that true? I wouldn't have expected that "true statement". That would mean that an isolated charge (like an electron) is attracted to neutral atoms.... I didn't know that was true...
  5. Jun 26, 2006 #4
    There must be a redistribution of charge if the surface of the conductor is to remain an equipotential. This induced polarization results in a potential that goes as 1/r4 (the usual dipole goes as 1/r2, plus an extra 1/r2 to account for the decreasing strength of the induced dipole with distance). This does have an analog in atomic/molecular interactions, often referred to as charge-induced dipole forces.
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