A capacitor is a device for storing charge. In this simulation, you can investigate a relatively simple capacitor, known as a parallel-plate capacitor. It consists of two identical metal plates, placed parallel to one another. The capacitor can be charged by connecting one plate to the positive terminal of a battery and the other plate to the negative terminal. In this situation, the battery acts as a pump, pumping electrons from one capacitor plate to the other until the potential difference across the capacitor matches the battery voltage.