1. Electric charges Q 20 and Q2 -3Q are placed at r =(1,0,0)a and r = (0,1,0)a. Find the electric field E at r = (0,0,1)a. 2. Four charged particles are placed at the corners of a square of side a. The charges are the following: -3Q (left top), 20 (right top), 2Q (left bottom), -30 (right bottom), Q> 0. Calculate the forces acting on each charge. Indicate the direction of these forces on the graph. Evaluate the formulas for the forces for 0 =