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Homework Help: Electric Feld Intensity Question

  1. Sep 10, 2011 #1
    1. The problem statement, all variables and given/known data
    An electric charge is distributed along an infinite line (2x+3y=7) in xy-plane with density pl = 3uC/m. Find the Efield intensity vector at point P (5,6).

    2. Relevant equations
    E = Integral of pl/ (4*pi*E) * (R - R')/ (R-R')^3

    3. The attempt at a solution
    I just wanted to double check if all i need to do is find the distance of point P from the y-int and x-int and then just use them as R and R' in the above equation
  2. jcsd
  3. Sep 11, 2011 #2

    rude man

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    Homework Helper
    Gold Member

    ?? Did you mean x-intercept & y-intercept? If so, i think the answer is no.

    Anyway - connect P(5,6) to the line at the point where they meet orthogonally. Call this distance r0.

    By symmetry, the direction of E is obviously in the direction of this normal in the +x, +y direction.

    The magnitude you can get by integrating k*dq/r^2 where r = r0sec(theta), k = 9e9 in SI units and theta is the angle between r0 and an element of charge along the line dq = pl*r*d(theta). Integrate from 0 to pi/2 & double the result.
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