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Electric potential midway between 2 charges

  1. Mar 21, 2007 #1
    Charges of −12.0 nC and −21.0 nC are separated by 0.700 m. What is the potential midway between the two charges?


    I used the equation V = kq / r for each charge
    and then added both V's. But I got it wrong. (the correct answer should be -847 V)
    So...


    V1 = (8.9x10^9)(-12 x 10^-9) / 0.7 = -152.6
    V2 = (8.9x10^9)(-21 x 10^-9) / 0.7 = -267

    V1 + V2 = -152.6 + (-267) = -420

    What am i doing wrong?
     
  2. jcsd
  3. Mar 21, 2007 #2
    maybe just algebra, the distance you need to use is the 1/2 way point of 0.35 see if that helps.
     
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