Three identical small balls , each of mass 0.1 gm ,are suspended at one point on silk thread having a length of L = 20 cm. What should charge imparted to the balls for each thread to form an angle of A= 30* with the vertical?

Three indistinguishable metallic plates are kept paralklel to each other at a seperation of an and b .The external plates are associated by a thin leading wire and charge Q is set on the focal plate then the charge on the internal period of plate C is Q/2.