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Voltage Help

  1. Apr 6, 2008 #1
    We wish to place a small charged sphere at a distance of 5.0 m from a point in space such that the voltage at that point is 1.20 V. How much charge should be on the sphere (in nC)?
  2. jcsd
  3. Apr 6, 2008 #2


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    What have you tried? What equations do you think you might need?
  4. Apr 6, 2008 #3
    I've tried V = kQ/r and V = kQ/r^2. If either of those are right, please respond, and if one of them is, then I feel I'm having conversion errors.
  5. Apr 6, 2008 #4
    r is essentially the distance (my teacher has been using 'radius' all this time)
  6. Apr 6, 2008 #5
    That second equation you're using with the r^2, dont use that one. The one you want to use is the first one. k is a constant and r is the radial distance (the question specifies that as 5.0m). If the voltage at that point is 1.20V, and you know the value of k and r, then just solve for Q.
  7. Apr 6, 2008 #6
    The answer comes out in Coulombs, right? How would I convert that to nanoCoulombs? Just multiply by 10^-9?
  8. Apr 6, 2008 #7
    Yea, in coulombs.

    u know 1 [nC] = 1E-9 [C]
    say you get x coloumb
    x [C] * 10^-9 [?]/1[?] ??
    you must learn to use those SI units
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