# Charges at the corners of a square.

#### msemsey

1. The problem statement, all variables and given/known data
Four positive charges are located on the corners of a square of side-length a.
The charges are A=4, B=2, C=8
4q----a----q
|------------|
a-----------a
|------------|
2q----a----8q

Determine the magnitude and direction of the electric field experienced by charge q in terms of q, a, and ke.

2. Relevant equations
Ex = [q1*q2/(4*∏*εo*a^2)]cosθ
Ey = [q1*q2/(4*∏*εo*a^2)]sinθ

3. The attempt at a solution

Ex = 4keq2/a^2 + 2keq2/[(2a2)^.5]cos45
Ey = [2keq2/(a*21/2)]sin45 + 8keq2/a2

I know I have to sum up the x components from A->q and B->q for the x component of the vector, and then sum up the y components from B ->q and C->q for the y component and then use the pythagorean theorum to find the magnitude. For the direction I have to take the tangent of the y-component/x-component. I am just confused because there aren't any values given. Would the above be correct?

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#### TSny

Homework Helper
Gold Member
Ex = 4keq2/a^2 + 2keq2/[(2a2)^.5]cos45
Ey = [2keq2/(a*21/2)]sin45 + 8keq2/a2
Check the expressions for the denominators.

#### msemsey

Check the expressions for the denominators.
I just went on fearofphysics.com (lifesaver) and have realized my error. I had the distance squared for one fraction, but not the other one. Thank you very much.

Edit: It WOULD be one of those errors.

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