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Homework Help: Electric field strength of a wire comparison

  1. Jan 26, 2010 #1
    1. The problem statement, all variables and given/known data

    The electric field strength 7.79 cm from a very long charged wire is 2660 N/C. What is the electric field strength (in N/C) 12.7 cm from the wire?

    2. Relevant equations

    E= (9*10^9) Q/ r^2

    3. The attempt at a solution

    i have energy. so is tried to solve backwards for the first one for Q. Then i plugged in the new Q with relation to 0.127 m. I got 1001 N/C which is wrong. Am I even using the right formula?
  2. jcsd
  3. Jan 26, 2010 #2
    Do you know Gauss's Law?
  4. Jan 26, 2010 #3
    ya is that what i needed to use?
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