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Homework Help: Work between two charges

  1. Sep 14, 2009 #1
    1. The problem statement, all variables and given/known data
    I get depressed and frustrated with every physics problem. The more studying and reading I do, the worse my grade gets. Talk about diminishing returns. Anyway, charges q1=1.65x10^-5 C and q2=-5.65x10^-5 C are placed 0.6 m apart. How much work must be done by an outside agent to move these charges slowly and steadily until they are 0.355 m apart?

    2. Relevant equations

    deltaV= -E*delta r
    -W=-qE*delta r

    3. The attempt at a solution
    Attempt at the solution is more than likely wrong
    deltaV= final-initial

    I got a really huge number. I used q=1.65x10^-5 because the positive charge will move to the negative charge.
  2. jcsd
  3. Sep 14, 2009 #2


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    What does V = k/r(q1+q2) represent? It is the electrostatic potential due to what? Are the charges in the denominator as the equation seems to imply?
  4. Sep 14, 2009 #3
    V=k*(q1+q2)/r is the equation to find the electric potential.
  5. Sep 14, 2009 #4
    That unfortunately gives the electric potential at a point that is equidistant from both charges q1 and q2 at a distance of r, and will not aid you at all in this question.
    You should consider how the overall potential energy of the system has changed.
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