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Homework Help: Calculating the electric potential

  1. Apr 23, 2010 #1
    1. Two point charges 2.0cm apart have an electric potential energy -180 microjoules. The total charge is 30 nanocoulombs. What are the two charges?
    Givens: change in postition = 0.02m , Q = 30nC = 3.0e-8C, V = -180 microjoules = 1.8e-4

    2. Relevant equations
    F = kq1q2/r^2
    E = kq/r^2

    3. The attempt at a solution
    E1 = (9.00e5) (3.0e-8C)/(0.02m^2)....?
  2. jcsd
  3. Apr 23, 2010 #2
    the question is asking "What are the two charges?", so if we say that one of them has a charge "a" and the other a charge "b" .. then you are asked to find what is "a" and what is "b" ..

    you are give r=2cm, electric potential= -180 microjoules, and a+b=30 nanocoulombs ..

    hint: you are asked to find two unknows, so you will need two equations.. one of them is given as a+b=30 .. find another equation from the given quantities ..
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