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Homework Help: Constant Electric Field and Potential

  1. Jan 31, 2009 #1
    1. The problem statement, all variables and given/known data

    The figure below shows two points in an electric field. Point 1 is at (X1,Y1) = (3,4), and point 2 is at (X2,Y2) = (12,9). (The coordinates are given in meters.) The electric field is constant with a magnitude of 59.3 V/m, and is directed parallel to the +X-axis. The potential at point 1 is 1200.0 V.

    prob02a_UEcoord34129.gif



    2. Relevant equations

    Vf-Vi = -Integral from i to f (E*ds)



    3. The attempt at a solution

    I set Vi=1200V
    E = 59.3 N/C
    and tried to solve for Vf

    I found the distance by making a triangle connecting the two points to be the sqrt(106) and the angle formed to be 29deg. I took the cos(29) and brought that out of the integral(Im not sure if thats right, but I saw my book take the cosine of the angle so I did too).

    Vf-1200 = -59.3*cos(29)*integral(from i to f) of (ds)

    I solved for Vf and got 1148 V, but thats wrong. Any suggestions
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Jan 31, 2009 #2

    gabbagabbahey

    User Avatar
    Homework Helper
    Gold Member

    Looks like you just plugged the numbers in wrong. I assume that you recognized [tex]\int_i^fds=\sqrt{106}[/tex]?
     
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