A point particle of mass M is attached to one end of a massless rigid non-conducting rod of length L. Another point particle of the same mass is attached to the other end of the rod. The two particle carry charges + q and – q respectively. This arrangement is held in a region of a uniform electric field E such that the rod makes a small angle θ (say of about 5°) with the field direction (see figure). The expression for the minimum time needed for the rod to become parallel to the field after it is set free.