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Homework Help: Find the Electric field strength at a point between two charges

  1. Mar 27, 2013 #1
    1. The problem statement, all variables and given/known data
    See images

    2. Relevant equations

    See images

    3. The attempt at a solution

    I have tried parts C and D several times, and the homework program is telling me that it's still not correct. For C, I keep getting:

    7.7x10^8 N/C

    for D I keep getting:

    7.1x10^-12 N/C

    In order to find these, I know you just plug in the known values into the equation from part A. But each time I plug these in, I get an incorrect answer. Please help. Thanks in advance!

    Attached Files:

  2. jcsd
  3. Mar 27, 2013 #2


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    For parts C & D please show your work, i.e. show exactly what numbers you are putting into your formula.

    You are using millimeters and nanoCoulombs, aren't you ?
  4. Mar 27, 2013 #3
    Oh! Units were the problem. Does this change the value of the permittivity constant from 8.85x10^-12 F/m to 8.85x10^-9 F/mm?
  5. Mar 27, 2013 #4
    That is correct. I fixed the problems. Thanks!
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