Capacitive Reactance

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Related to Capacitive Reactance: Inductive reactance

capacitive reactance

[kə¦pas·əd·iv rē′ak·təns]
Reactance due to the capacitance of a capacitor or circuit, equal to the inverse of the product of the capacitance and the angular frequency.

Reactance, Capacitive


a quantity characterizing the opposition presented to an alternating current by the capacitance of a circuit or of part of a circuit. Capacitive reactance is measured in ohms.

In the case of a sinusoidal current, the capacitive reactance xcc can be expressed as the ratio 1/ωC, where ω is the angular frequency of the current and C is the capacitance of the circuit. Capacitive reactance is equal to the ratio of the amplitude of the voltage applied to the terminals of a circuit and the amplitude of the current through the circuit if the circuit has a capacitive character (that is, has little inductance and resistance); such a circuit can be regarded as equivalent to a capacitor. If ω 4 0, the variation in the voltage across the capacitor causes a variation in the charge on its plates. As a result, a charging (discharge) current flows continuously in the circuit of the capacitor. During the charging and discharging of the capacitor, electrical energy is periodically transferred from the current source to the electric field of the capacitor and then back to the current source; the average power during a period is equal to zero.

References in periodicals archive ?
Coplanar capacitive feed strip has been modified to tune out the capacitive reactance and match the input impedance.
The choices between a capacitive and an inductive reactance at the lower and higher band edge impedances, for the input impedance and an inductive and a capacitive reactance at the lower and higher hand edge impedances, respectively, for the input impedance after the first step in the design process are determined mainly by the location of the original dispersive impedance on the Smith chart coupled with the desire to use a transmission line length that is as short as possible in step 1.
However, as shown in Figure 1, the input capacitive reactance eventually will follow the same -20-dB/decade slope for both active and passive probes.
The denominator's dominant term is the capacitive reactance for [Theta] near 90 [degrees].