What happens if you pull the plates of an isolated charged capacitor apart?

If you pull the plates of an isolated charged capacitor apart, the capacitance decreases because capacitance is inversely proportional to the distance between the plates. As the distance increases, the electric field between the plates weakens, leading to a rise in voltage across the capacitor. Consequently, the stored energy increases, as energy is given by the formula ( U = \frac{1}{2} C V^2 ). Therefore, the capacitor's voltage increases while the total charge remains constant.