Van de Graaff accelerators are another form of electrostatic separation of charge. In one accelerator, the potential difference to ground is 5 MV, and charges of 20 C are accumulated on the sphere. How much energy is stored in such a device? Air breaks down (ionizes) at 3x10^6 N/C. If the accelerator were in air, give an estimate for the minimum separation between the conducting sphere and the ground? Assume the sphere radius is very large so that it looks like a parallel-plate capacitor near the bottom of the sphere