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X and y componants of electric field

  1. May 9, 2015 #1
    1. The problem statement, all variables and given/known data

    2. Relevant equations

    3. The attempt at a solution

    I understand the magnitude part, and I'm probably being really stupid here but I cant see how he has got the x and y values for the componants (circled in red). If anyone could help it would really be appreciated.
  2. jcsd
  3. May 9, 2015 #2


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    You have [tex]\vec E = |E|(\cos \theta\,\vec x + \sin \theta\,\vec y)[/tex] for some [itex]\theta[/itex]. Given the horizontal dimensions of the sheet, what are [itex]\cos \theta[/itex] and [itex]\sin \theta[/itex]?

    To calculate [itex]|E|\cos \theta[/itex] and [itex]|E|\sin \theta[/itex] you should use the exact value of [itex]|E|[/itex], not the approximation 223.61 kV/m.
  4. May 9, 2015 #3
    Thats very helpful. Thankyou! Although for some reason I get 200 for [itex]|E|\cos \theta[/itex] and 100 for [itex]|E|\sin \theta[/itex]. But I'm happy just to understand the method he used. Thanks!!!
  5. May 9, 2015 #4


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    You may have interchanged [itex]\vec x[/itex] and [itex]\vec y[/itex]. Note that in the diagram the longer side of the sheet is parallel to the y-axis, which is horizontal across the page.
  6. May 9, 2015 #5
    Ahhhh, didnt notice the axis. Thank you!
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