the circuit in fig. 32-31 consists of switch s, a 12.0 v ideal battery, a 20.0 m resistor, and an air-filled capacitor. the capacitor has parallel circular plates of radius 5.00 cm, separated by 3.00 mm. at time t 0, switch s is closed to begin charging the capacitor. the electric field between the plates is uniform. at t 250 ms, what is the magnitude of the magnetic field within the capacitor, at radial distance 3.00 cm?