1. Electric charges Q, = 20 and Q2 - -30 are placed at r, = (1,0,0)a and r2 = (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: -30 (left top), 20 (right top), 20 (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 =