1. Two point charges each of mass m and charge q are suspended by strings of length l from a common point. Find the value of q for which the angle made by the strings at the common point is 90°.
2. Point charges Q and are situated at (0, 0, 1) and (0, 0, ), respectively. Find the approximate electric field intensity at (a) (0, 0, l00), and (b) (100, 0, 0).