2. Two concentric conducting spheres are charged such that the inner one has a charge of 2q and the outer has a charge of - q. The inner sphere has a radius a, the outer sphere has an inner radius b, as shown below. (a) Explain why the electric field is zero inside the inner conducting sphere. [3] (b) Show that the potential difference between the inner sphere and inner radius of the outer sphere is given by 9 V - V = -(b-a) 2 ab 2q -9 [6]