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Homework Help: Thin Rod + Poncual Charge Find Vb-Va

  1. Oct 1, 2008 #1
    Thin Rod + Poncual Charge.... Find Vb-Va

    1. The problem statement, all variables and given/known data
    A thin "rod" of 10 m is located between (0m,4m) and (0m,14m). Its linear density is 50*10^-9C/m. Also, there is a ponctal charge of Q=10*10^-9 located at (-1m,0m).
    Given 2 points:
    A at (0m,-5m)
    B at (0m,0m)
    Find Vb-Va.

    2. Relevant equations
    E=k|Q|/r^2
    E*d=V
    some integrals...


    3. The attempt at a solution
    Okay, this seems like a tricky one, does it not?
    I know I could use Vb-Va = Integral of : E*s, possibly with s=5
    But then, I would have a Vb-Va for the rod, would I have to also calculate the Vb-Va due to the poncyal charge and then sum these 2? This is what I would have done during an exam, though I'm really not sure it'd be good, would it?

    Thanks for any help you can provide... belive me, I,ve tried it a couple of times before posting here.:wink:
     
  2. jcsd
  3. Oct 1, 2008 #2
    Re: Thin Rod + Poncual Charge.... Find Vb-Va

    Ok, so i've tried something, not sure though...
    I could separate the question in finding :
    -Vb : Vb-from the rog + Vb from the charge
    -Va : Va-from the rog + Va from the charge
    And then simply substract...is this it? Im not sure but i just think it could...

    Thanks for helping
     
  4. Oct 2, 2008 #3
    Re: Thin Rod + Poncual Charge.... Find Vb-Va

    I managed to find a number, but as I do not have the answer key, i can't tell if it's good. So if somebody is able to do it, maybe then we could compare our answers :)
    this would be really appreciated
     
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