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Homework Help: Electric Field Question

  1. May 24, 2010 #1
    1. The problem statement, all variables and given/known data
    A point charge q = 2.7 x 10^-6 C is placed at each corner of an equilateral triangle with sides of .11 m in length. What is the magnitude of the electric field at the midpoint of any of the 3 sides of the triangle.

    2. Relevant equations
    F = kqq/r^2
    E = F/q

    3. The attempt at a solution
    F = k(2.7x10^-6)^2/.055^2
    F = 21.66 N

    Since there are two forces acting at this point
    2 x 21.66 = 43.22 N is the total force.

    E = F/q
    43.22 N/2.7x10^-6C
    = 16007407 N/C
  2. jcsd
  3. May 24, 2010 #2
    the intensity due to the 2 charges on the same side of the triangle ( where d point is taken) cancel out since the charges are of same nature ( forces act in opposite directions). so the net field is contributed only by the charge on opposite vertex.
  4. May 25, 2010 #3
    I always believe that when you have a problem such this, it is better to draw a simple figure to be sure that what you are doing is right ..

    so for your problem see the following figure:

    http://img28.imageshack.us/img28/1414/64786042.jpg [Broken]

    figure (1) represents your problem, you have identical charges at the croners of the triangle..

    lets consider the situation (figure (2) ) where we want to find the field at the midside (the one on the left) .. notice carefully the directions of the fields from each charge , what can you conclude?
    Last edited by a moderator: May 4, 2017
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