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In electrical engineering, impedance is the opposition to alternating current presented by the combined effect of resistance and reactance in a circuit. [1]Quantitatively, the impedance of a two-terminal circuit element is the ratio of the complex representation of the sinusoidal voltage between its terminals, to the complex representation of the current flowing through it. [2]
Electronic symbol. In electrical engineering, a capacitor is a device that stores electrical energy by accumulating electric charges on two closely spaced surfaces that are insulated from each other. The capacitor was originally known as the condenser, [1] a term still encountered in a few compound names, such as the condenser microphone.
An assortment of electrolytic capacitors. An electrolytic capacitor is a polarized capacitor whose anode or positive plate is made of a metal that forms an insulating oxide layer through anodization. This oxide layer acts as the dielectric of the capacitor. A solid, liquid, or gel electrolyte covers the surface of this oxide layer, serving as ...
Voltage divider. In electronics, a voltage divider (also known as a potential divider) is a passive linear circuit that produces an output voltage (Vout) that is a fraction of its input voltage (Vin). Voltage division is the result of distributing the input voltage among the components of the divider. A simple example of a voltage divider is ...
Equivalent impedance transforms. An equivalent impedance is an equivalent circuit of an electrical network of impedance elements [note 2] which presents the same impedance between all pairs of terminals [note 10] as did the given network. This article describes mathematical transformations between some passive, linear impedance networks ...
Pseudocapacitors were named for their ability to store electric energy electro-chemically with reversible faradaic charge-transfer. Hybrid capacitors combine double-layer and pseudocapacitors to increase power density. Silver mica, glass, silicon, air-gap and vacuum capacitors are named for their dielectric.
In general, capacitance is a function of frequency. At high frequencies, capacitance approaches a constant value, equal to "geometric" capacitance, determined by the terminals' geometry and dielectric content in the device. A paper by Steven Laux [27] presents a review of numerical techniques for capacitance calculation.
Ideally, the impedance of a capacitor falls with increasing frequency at 20 dB/decade. However, due partly to the inductive properties of the connections, and partly to non-ideal characteristics of the capacitor material, real capacitors also have inductive properties whose impedance rises with frequency at 20 dB/decade.