Question

Four point charges have the same magnitude of 2.62 10-12 C and are fixed to the corners of a square that is 3.80 cm on a side. Three of the charges are positive and one is negative. Determine the magnitude of the net electric field that exists at the center of the square.

Answer 1

Symettry. Two opposite charges must be +, so they cancel E since opposite directions. tHe other two add, so E=k2q/distance^2

where distance is 0ne half of the diagonal.