A parallel plate capacitor is charged and then disconnected from the charging battery. If the plates are now…
A parallel plate capacitor is charged and then disconnected from the charging battery. If the plates are now moved further apart by pulling them by means of insulting handles, then
the capacitance of the capacitor increases
the voltage across the capacitor increases
the energy stored in the capacitor decreases
the charge on the capacitor decreases
Solution
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 $\frac{A \varepsilon_0}{d}$. When the plate is separated, the distance between the plate $d$ increases and hence the capacitance decreases.
Hence, according to the $Q=C V$ relation, the voltage across the capacitor increases in order to keep the charge constant.