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Homework Help: Graphing the flux density between two line charges in matlab

  1. Feb 19, 2015 #1
    1. The problem statement, all variables and given/known data
    I am trying to graph the flux density field between two infinite line charges located at y = 1 and y = -1

    2. Relevant equations
    I am trying to do it using the equation for a line charge that I got from lecture notes.

    The above equation is derived from this:
    Here is the proof http://puu.sh/g4E0V/68d2790871.png [Broken]
    My friend successfully graphed the field using this equation and using a nested loop to sum the pieces of the line up at each point, but I chose another way and am having trouble.

    3. The attempt at a solution
    I tried doing it by solving using the line charge field equation at every point rather than using a loop, but ended up with a different wrong result. This is my code.

    In my code what I call x and y are respectively z and p in that yellow diagram above.

    min = -5;
    max = 5;
    num = 50;
    step = (max - min) / (num-1);
    [X,Y]=meshgrid(-5:step:5,-5:step:5);%build arrays of plot space

    Fx=zeros(num,num);%x component of flux density
    Fy=zeros(num,num);%y component of flux density

    pL1=1e-6;%top line charge density
    pL2=-1e-6;%bottom line charge density

    for i=1:num
    for j=1:num
    %cos = x / h
    %sin = y / h
    x = X(i,j);
    y = Y(i,j);

    Fy(i,j) = (pL1 / (2*pi*(y-1))) * 1;
    Fx(i,j) = (pL1 / (2*pi*(y-1))) * 0;
    Fy(i,j) = Fy(i,j) + (pL2 / (2*pi*(y+1))) * 1;
    Fx(i,j) = Fx(i,j) + (pL2 / (2*pi*(y+1))) * 0;



    Help is much appreciated.
    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Feb 25, 2015 #2
    Thanks for the post! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
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