A capacitor is a component designed to store electric charge and electrical energy (potential energy). A system consisting of one conductor enclosed by another-or, more generally, a system in which all electric field lines originating from one conductor terminate upon another-is referred to as a capacitor.
In this context, UA-UB represents the potential difference between the two parallel plates; εr denotes the relative permittivity; k is the electrostatic constant; S represents the surface area of the plates facing each other; and d is the distance between the plates. Note: The electric field within a parallel-plate capacitor is a uniform electric field.
Capacitance is distinct from a capacitor. Capacitance is a fundamental physical quantity, designated by the symbol C, and measured in units of F (farads).
The general formula is C = Q/U; for parallel-plate capacitors specifically, the electric field strength between the plates is given by E = U/d.