Four tiny spheres are charged to some charge value of "q". They are assembled to form a square with each side a length of "d". Half of the spheres are positively charged while the other half is negatively charged. Find the magnitude (in terms of q and d) and the direction of the electric field created by the four spheres at the center of the square. Assume that these tiny balls behave like point charges.

• A. $\frac{4\sqrt2kq}{d^2}$ , in the negative y-direction
• B. $\frac{2\sqrt2kq}{d^2}$ , in the negative y-direction
• C. $\frac{4\sqrt2kq}{d^2}$ , in the positive y-direction
• D. $\frac{2\sqrt2kq}{d^2}$ , in the positive y-direction

Answer: (A)