Calculating Electric Field at Origin for Rotated Square of Positive Charges

AI Thread Summary
The problem involves calculating the electric field at the origin due to three positive charges located at the corners of a square rotated 45 degrees with respect to the x-axis. The charges are positioned at (-a, 0), (a, 0), and (0, -a). It is noted that the contributions from the charges at (-a, 0) and (a, 0) will cancel each other out, leaving only the charge at (0, -a) to influence the electric field at the origin. The discussion also touches on the relationship between electric potential and electric field, with a formula provided for calculating the electric field. The overall consensus is that the problem may be simpler than initially perceived, focusing primarily on the effect of the single charge at (0, -a).
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1. Three posative charges +Q lie on the corners of a square which is rotated 45 degrees with respect to the x-axis. Calculate the electric field at the origin, in terms of the variables Q and a.

I think this question is much easier than I think it is but I'm stuck on it. There is a picture along with this problem but it isn't very complex so i'll describe it here. As stated in the problem the square is rotated 45 degrees with respect to the x axis. Then the 3 charges +Q are located at 3 corners located at: (-a, 0), (a, 0) and (0, -a). I'm assuming this is an Electric Potential Energy problem because it comes in that section of the homework (however, this may not be the case).

So far I've got out of my notes that V = -Edcos(ø). Solving for E gives: E = -(V/dcos(ø))

I've also noticed that the charges at (-a, 0) and (a, 0) will cancel each other out leaving only (0, -a) affecting the force on the origin. I know that I could also substitute EPE/q for V, but I don't think this is the route to go.
 
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