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Homework Help: E field

  1. Feb 24, 2012 #1
    1. The problem statement, all variables and given/known data
    Consider two equal positive charges (q=+2.0 µC) a distance of 3.0 cm apart. What is the electric potential midway between the two charges? What is the E field at this point?

    I got the work and everything all solved out, i just don't know where some of the numbers came from. Where does the 2 before K come from, I understant the q= 2X10^-6, but why is r 1.5x10^-2? I am just wondering where some of the numbers came from.

    2. Relevant equations
    kq/r=E


    3. The attempt at a solution
    look at attachment
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     

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  3. Feb 25, 2012 #2

    tiny-tim

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    hi sasuke07! :smile:
    that equation is kqL/rL + kqL/rL = 2kq/r …

    they're defining qR = qL = q and rR = rL = r :wink:

    (and r is half of 3.0 cm)
     
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