A large model of a parallel plate capacitor connected to an electroscope shows changes in voltage as the plate spacing is varied. By moving the plates closer together or farther apart, the capacitance changes, which is reflected in the deflection of the electroscope needle. This demonstration illustrates the inverse relationship between capacitance and plate separation, as well as the concept that capacitance is directly proportional to the plate area and inversely proportional to the distance between the plates. A dielectric material can also be slid in between the capacitor plates to show a decrease in voltage from the increase in capacitance, due to the constant charge stored in the capacitor.