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Homework Help: Electric Field of a Straight Wire (now with the attachment)

  1. Feb 5, 2012 #1
    1. The problem statement, all variables and given/known data
    The word document with the problem is attached below.


    2. Relevant equations
    dE=kdQ/r22
    Ex=Ecos∅

    3. The attempt at a solution
    dE=kdQ/r2
    E=kλ∫dy/(x2+y2) (integrating from y= -L/2 to L/2)
    Ex=2kλ∫xdy/(x2+y2)3/2 (change integration to y= 0 to L/2, multiplying expression by 2)

    Let y=xtan∅
    dy=x(sec∅)2 d∅

    =2kxλ∫x(sec∅)2/x3(sec∅)3 d∅
    =2kλ/x∫cos∅ d∅
    =2kλ/x(sin∅)
    =2kλ/x(sin(arctan(y/x)) (evaluated from y=0 to y=L/2)
    =2kλ/x(y/(x2+y2)1/2 (evaluated from 0->L/2)
    =2kλ/x(L/2)(x2+(L2)/4)1/2
    =((1.8X10^10)λL/(2x))*(1/x2+(L2)/4)1/2

    This isn't the correct answer, though I don't know what actually is. I would appreciate any help or guidance!
     

    Attached Files:

  2. jcsd
  3. Feb 5, 2012 #2
    Okay, I figured it out. I am using an online HW program and it just wanted the the answer in terms of epsilon, not a numerical value. Thanks anyway!
     
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