(a) Using the symmetry of the arrangement, show that the electric field at the center of the square in figure 18.46 is zero if the charges on the four comers are exactly equal.Show that this is also true for any combination of charge in which qa= qb = and qc = qd . (b) Calculate the magnitude of the electric field at the location of q, given that the square is 5.00 cm on a side.
