Reactance And Frequency:

The Capacitive reactance behaves in many ways such as a mirror image of inductive reactance. In other logic, though, X_C is an extension of X_L into negative values-below zero-with its own unusual set of characteristics.

When the frequency of an ac source is provided in hertz as f and the capacitance of a capacitor in farads is provided as C, then the capacitive reactance is as follows:

X_C = -1/(2ΠfC) = -(2ΠfC)^-1

      ≈ -(6.2832fC)^-1

This similar formula exerts if the frequency is in megahertz (MHz) and the capacitance is in microfarads (μF). Recall that when the frequency is in millions, the capacitance should be in millionths. This formula also would exert for frequencies in kilohertz (kHz) and millifarads (mF), though for some reason, you will almost never see millifarads used in practice. Even millifarads are very large units for capacitance; components of more than 1,000μF (that would be 1 mF) are seldom found in real-world electrical systems.

The Capacitive reactance differs inversely with the frequency. It means that the function X_C versus f emerges as a curve whenever graphed, and this curve "blows up negatively" as the frequency nears zero. The Capacitive reactance also differs inversely with the real value of capacitance given a fixed frequency. The function of X_C versus C also emerges as a curve which "blows up negatively" as the capacitance approaches to zero. The negative of X_C is inversely proportional to frequency, and also to capacitance. Relative graphs of such functions are shown in figure shown below.

Figure: Capacitive reactance is inversely proportional to the negative of the capacitance, and also to the negative of the frequency.