In an experiment a ring jumped up due to induced eddy currents, but the ring did not jump when there was a gap in the ring. If we could make the electric field large enough, a spark could occur in the gap closing the current loop and allowing the ring could jump. We want to figure out under what conditions that could happen. Consider the solenoid to be an ideal cylindrical solenoid of radius R. The ring slips closely over the solenoid so it also has radius R. The magnetic field within the solenoid varies sinusoidally as B = B₀cos(?t). Assume ? is fixed (maybe it's just the standard f = 60 Hz), but we can change B₀. The breakdown electric field of air is E₀. How large must B₀ be in order to make a spark across the gap?