A capacitor (originally known as a condenser) is passive two-terminal electrical component used to store energy electrostatically in an electric field. The forms of practical capacitors vary widely, but all contain at least two conductors (plates) separated by dielectric (i.e., insulator). can be thin films metal, aluminum foil or disks, etc. 'nonconducting' acts increase the capacitor's charge capacity. glass, ceramic, plastic film, air, paper, mica, Capacitors are widely parts circuits many common devices. Unlike resistor, does not dissipate energy. Instead, stores form electrostatic field between its plates. When there potential difference across (e.g., when attached battery), develops dielectric, causing positive (+Q) collect on one plate and negative (-Q) other plate. If battery has been for sufficient amount time, no current flow through capacitor. However, if accelerating alternating voltage applied leads capacitor, displacement flow. An ideal characterized single constant value capacitance. Capacitance expressed ratio (Q) each conductor (V) them. SI unit capacitance farad (F), which equal coulomb per volt (1 C/V). Typical values range from about 1 pF (10−12 F) mF (10−3 F). greater narrower separation have larger surface area. In practice, plates passes small leakage also strength limit, breakdown voltage. introduce undesired inductance resistance. electronic blocking direct while allowing pass. analog filter networks, they smooth output power supplies. resonant tune radios particular frequencies. transmission systems stabilize