Capacitor: Electrodes, Dielectric and Capacitance

A capacitor is a passive electrical component that stores separated electric charge. Its basic structure has two conducting electrodes separated by an insulating material called a dielectric. Capacitance describes the charge stored per unit voltage; it is a property of the component, rather than another name for the component. ROHM capacitor structure · Murata capacitance explanation

Electrodes and dielectric

The electrodes provide the conducting surfaces. The dielectric separates them electrically. Applying a voltage produces a separation of charge, and changing the voltage changes the stored charge. The two-electrode explanation is a basic model; real constructions may use multiple layers or wound arrangements. ROHM basic structure and construction forms · Murata charging explanation

Capacitance and the farad

Capacitance is commonly represented by C and measured in farads (F). One farad corresponds to one coulomb of stored charge per volt. Electronic component values often use smaller units such as microfarads (µF), nanofarads (nF) and picofarads (pF). These describe capacitance, not a voltage rating. Murata capacitance definition · ROHM units

In the basic parallel-plate model, capacitance increases with electrode area and dielectric permittivity, and decreases as the spacing between the electrodes increases. This explains the role of geometry and material; it does not provide a universal calculation for every capacitor construction. ROHM capacitance relationship · Murata electrode-area explanation

Does a capacitor block DC?

Connecting a capacitor to a DC voltage can produce a charging current. In the ideal model, that current ceases after charging is complete and the voltage remains constant. A changing voltage can produce repeated charging and discharging. “Blocks DC” therefore describes the ideal steady condition, rather than an absence of current at every moment after connection. Murata charging and discharging

Real insulation is not perfect. Murata’s ceramic-capacitor explanation distinguishes the initial charging current from absorption current and the small leakage current that can remain. This is why the ideal steady-state description should not be taken as a guarantee of zero current in a real component. Murata insulation resistance and leakage

Capacitance, voltage rating and type

Capacitance and rated voltage describe different properties. Murata discusses how dielectric thickness affects both voltage capability and capacitance in aluminum electrolytic construction; one value cannot be substituted for the other. Murata aluminum electrolytic construction

Capacitor families include ceramic, film and electrolytic forms. Some constructions are polarized: aluminum electrolytic capacitors are one example. Polarity is not a universal requirement for every capacitor type. Murata capacitor families and aluminum electrolytic polarity · ROHM type distinctions

For resistance and heat dissipation, see resistor basics. The electronic components section connects related definitions. These distinctions explain the component; they do not establish a suitable capacitor, operating voltage or test method for a circuit.