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Homework Help: Electric fields

  1. Jul 30, 2010 #1
    1. The problem statement, all variables and given/known data

    [PLAIN]http://img197.imageshack.us/img197/5497/phys.jpg [Broken]

    2. Relevant equations


    3. The attempt at a solution

    I just want to confirm some of my answers and clarify some things.

    For (a): Ex=1.10MN/C and σ/2ε = 1.19MN/C and σ/2ε is 8.08% greater than Ex.

    For (b): Ex=0.0865MN/C and E(pt charge)=0.437MN/C and E(pt charge) is 506% greater than Ex...

    I'm not too sure about the percentage increases though so it'd be greater if someone could clarify that.

    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Jul 31, 2010 #2
    You can manipulate the expression given so that it becomes σ/2ε[1-r2/r2+x2].
    You can see as x increases the actual field decreases hence the approximated field becomes larger.
  4. Aug 1, 2010 #3
    Yeah... I'm not too confident about the % comparisions... could someone check those please?

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