capacitor
19.5 Capacitors and Dielectrics A capacitor is a device used to store electric charge. Capacitors have applications ranging from filtering static out of radio reception to energy storage in heart defibrillators. Typically, commercial capacitors have two conducting parts close to one another, but not touching, such as those in Figure 19.13. Most of the time an insulator is used between the two plates to provide separationsee the discussion on dielectrics below. When battery terminals are connected to an initially uncharged capacitor, equal amounts of positive and negative charge, +Q and Q , are separated into its two plates. The capacitor remains neutral overall, but we refer to it as storing a charge.