Which term refers to a device used to store energy electrostatically, formed by two plates?

• A. Commuter
• B. Conductor
• C. Capacitor
• D. Circular Mil

Answer: (C)

A capacitor stores energy in the electric field created between two conductive plates separated by an insulating material (dielectric). When you apply a voltage, charges accumulate on the plates—positive on one plate and negative on the other—producing an electric field that fills the space between them. The energy is stored in that field, not in the material itself or in the motion of electrons. The amount of energy stored depends on the capacitance C and the voltage V, with the stored energy given by W = 1/2 C V^2. Capacitance for a simple parallel-plate arrangement is C = ε A / d, where A is the plate area, d is the separation, and ε is the dielectric permittivity (ε = ε_r ε_0). This contrasts with a conductor, which is a material that readily allows charge to move, and with Circular Mil, a unit of wire cross-section; neither of these describe a device that stores energy electrostatically between two plates.