A is obviously zero.
For b the two points on either side of the midpoint cancel. Then you are going to need to do a little geometry and trig to find the component pushing it down (away from the center). The magnitude is just kq/r^2, and the angle will be tan-1 ((a/2)/a) or tan-1(1/2)
Four identical positive charges q are placed at the four vertices of a square of side a. Determine the electric field:
A) at the center of the square
B) at te midpoint of one of its sides
1 answer