1)Two small equally charged spheres, each of mass m, are suspended from the same point by silk threads of length l.The distance between the spheres x<<l.Find the rate dq/dt with which the charge leaks off each sphere if their approach velocity varies as v=a/(x)^0.5, a is a constant. The problem can be done by expressing q^2 in equilibrium condition and then differentiating w.r.t. time.But I wonder why the charge leakage will occur?What principle makes it and how? 2)A thin wire ring of radius R has an electric charge q. What will be the increment of the force streatching the wire if a point charge qo is placed at the ring's centre? It appeared to me that the direct mathematical formulation of E field, inside and outside the ring is rather difficult.so i tried to calculate the potential due to the ring and point charge.But, the integration to find contribution of the ring turned hopelessly difficult.Please help. Kolahal Bhattacharya.