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Homework Help: Potential difference please help

  1. Jan 17, 2008 #1
    Potential difference please help!!

    1. The problem statement, all variables and given/known data
    It takes 3.3 μJ of work to move a 34.26 nC charge from point A to B. It takes -3.3 μJ of work to move the charge from C to B. What is the potential difference VC-VA?

    2. Relevant equations
    Uel = qV

    3. The attempt at a solution
    Don't I just find the difference between A and C?
    Vc = Uelc * qc = 1.13x10^-13
    And Va would be the same so I know I am not understanding this.
  2. jcsd
  3. Jan 17, 2008 #2

    Tom Mattson

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    Let's do this in pieces.

    Since only potential differences are physically significant, you can set the potential at zero at any point you want. Let's set [itex]V_A=0[/itex]. Since it takes negative work to move a charge from A to B, is [itex]V_B[/itex] less than, greater than, or equal to [itex]V_A[/itex]? Can you compute [itex]V_B[/itex]?
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