A capacitor is an electrical component that can temporarily store a small electric charge. If two metal plates are positioned close together, but not touching, they form a capacitor. Fixing one end of a battery to each plate will charge the capacitor, i.e. cause a positive charge to flow into one plate and a corresponding negative charge into the other. If a wire ever connects the two plates, a brief surge of current will flow as the charges equalize. Capacitors are shown in Fig. 5.6.1: