1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook