Big cap. The unit of capacitance is the farad. A capacitor with C = 1 F is a large one; although such capacitors do exist, most applications use capacitors with capacitances in the range of mF, µF, nF, or even pF (picofarads, known affectionately as “puffs”). 

(a) To get a sense of how big a unit the farad is, find the area of a hypothetical 1.0-F parallel-plate air capacitor, where the plates are separated by d = 2.0 mm. 

(b) Find the plate area if we fill the capacitor gap with the excellent dielectric strontium titanate. Give your answers to both parts (a) and (b) in units of square meters, square kilometers, and square miles.