Answer
a) greater than
b) I
Work Step by Step
(a) We know that the charged capacitor has more mass because it is storing energy within it, just like a compressed spring. Thus, the mass of the charged capacitor is greater than the mass of the uncharged capacitor.
(b) We know that the best explanation is option (I) -- that is, the charged capacitor has more mass because it is storing energy within it, just like a compressed spring.
