AC Capacitance

The following figure shows a capacitor in an AC circuit. In this, voltage exists across the plates of the capacitor only after the flow of current charges the plates.

FIGURE

        The following is the waveform diagram and the phasor diagram that represents the capacitance in an AC circuit. In a pure capacitance circuit, the current leads the voltage by 90^o.

FIGURE

FIGURE

        The opposition of a capacitor to any changes in the value of the voltage applied to it is known as capacitive reactance, which is calculated using the formula below.

X_C = capacitive reactance (ohms)

f = frequency (Hertz)

C = capacitance (Farads)

        The power in a capacitive circuit is shown in the figure below. It is understood that there are two positive peaks and two negative peaks of power over one complete cycle, thus the net power is zero.

FIGURE