unable 2 solve...............plz help me..........

!)A thin conducting wire of radius R has a charge +Q.show that the increase in the tension of the wire when a pt. charge +q is placed at the centre of the ring is given by T=qQ/ 8(pi)²(episilon)R²

2)A simple pendulum consists of a small sphere of mass suspended by a thread of length l .the sphere carries a +ve charge Q.The pendulum is placed in a uniform field of strength E directed vertically upwards.With what period will the pendulum oscillate if the the electrostatic force acting on the sphere i s less than the gravitational force(Assume the oscillations 2 b small) Ans:-2pi√[{1/(g-qE/m)}