# Electric fields of triangle

1. Jan 29, 2007

### map7s

1. The problem statement, all variables and given/known data
A point charge q = +2.6 µC is placed at each corner of an equilateral triangle with sides 0.13 m in length.
What is the magnitude of the electric field at the midpoint of any of the three sides of the triangle?

2. Relevant equations
E=(kq)/r^2
Fx=(F1+F2)cos
Fy=(F1+F2)sin
F=Fx+Fy

3. The attempt at a solution
I first tried using the first equation, but I was pretty sure that I had to also use the other three equations, but I did not know how to properly solve for each of the F values. Am I supposed to use F=(kq1 q2)/r^2 ?

2. Jan 30, 2007

### antonantal

Do this formulas seem right to you? Where are the arguments of cos and sin?

In general, when dealing with problems of physics, you should try to visualize them, not treat them just like a system of equations. It's much easier if you make a drawing and see what forces act on that point and what are the angles between them.

So you should begin by drawing the three point charges in the corners of an equilateral triangle, and draw the vectors representing the electric fields produced by each point charge, at the midpoint of a side of your choice.

You will only need one formula which you mentioned $$E={k}\cdot\frac{q}{r^2}$$ and the rules of vector addition.

Also you should think why it doesn't matter which side's midpoint you take.