kapacitans

Kapacitans, or capacitance, is the ability of a system to store electric charge in an electric field. It is defined as the ratio of the stored charge Q to the potential difference V between two conductors: C = Q/V. The capacitance is a property of a component or circuit, and for linear devices it does not depend on Q or V, within the device's operating range. The unit is the farad (F).

For simple geometries, capacitance depends on geometry and the material between conductors. For a parallel-plate capacitor: C = ε A / d, where A is plate area, d separation, and ε is the permittivity of the dielectric between the plates; ε = ε0 εr, with ε0 ≈ 8.854×10^-12 F/m and εr the relative permittivity of the dielectric. A higher εr or larger area and smaller separation increase C. Dielectric properties also determine breakdown voltage and temperature stability.

Capacitors are common components: ceramic, electrolytic, film, mica, and others. They may be fixed or variable. When several capacitors are connected in a circuit, the total capacitance is C_eq determined by series and parallel rules: for series, 1/C_eq = Σ 1/C_i; for parallel, C_eq = Σ C_i.

Capacitance plays a central role in timing, filtering, energy storage, and decoupling in electrical and electronic systems. The energy stored in a charged capacitor is U = 1/2 C V^2. In alternating current circuits, the capacitor presents an impedance Z = 1/(j ω C) and a reactance Xc = 1/(2π f C).