Physics - Capacitor Question with Solution | TestHub

When the capacitor is charged and then disconnected, the charge across the plates remains a constant, even when the plates are separated. The capacitance is related to the structure of parallel plate capacitor as $\frac{A{\epsilon }_0}{d}$. When the plate is separated, the distance between the plate $d$ increases and hence the capacitance decreases. Hence, according to the $Q=CV$ relation, the voltage across the capacitor increases in order to keep the charge constant.