What is Capacitive Reactance?

Capacitive reactance (symbolized as Xc) is the opposition offered by a capacitor to the flow of alternating current (AC). Unlike a standard resistor, which provides a fixed resistance regardless of frequency, a capacitor's "resistance"—or reactance—changes depending on the frequency of the electrical signal passing through it.

Measured in Ohms (Ω), capacitive reactance is inversely proportional to both the frequency of the supply and the capacitance of the component. This means that as frequency increases, the reactance decreases, allowing more current to flow.

The Capacitive Reactance Formula

Where:

• Xc = Capacitive Reactance in Ohms (Ω)
• π (Pi) ≈ 3.14159
• f = Frequency in Hertz (Hz)
• C = Capacitance in Farads (F)

How to Use This Calculator

Using our capacitive reactance calculator with steps is simple. Follow these instructions for accurate results:

1. Enter Frequency: Input the frequency of your AC signal and select the appropriate unit (Hz, kHz, or MHz).
2. Enter Capacitance: Input the value of your capacitor. Most electronic capacitors are labeled in microfarads (µF), nanofarads (nF), or picofarads (pF). Ensure you select the correct unit from the dropdown.
3. Calculate: Click the calculate button to see the result and the full mathematical breakdown of the conversion and formula application.

Why Does Reactance Change with Frequency?

In a DC circuit, a capacitor eventually charges to the source voltage and then acts as an open circuit (infinite resistance). However, in an AC circuit, the voltage constantly reverses direction. The capacitor is constantly charging and discharging. At higher frequencies, there is less time for the capacitor to charge up and oppose the voltage, resulting in lower reactance. This unique property makes capacitors essential for filters, tuning circuits, and power factor correction in electrical engineering.

Frequently Asked Questions

What happens to Xc if frequency is doubled?

Because the relationship is inverse, if you double the frequency (f), the capacitive reactance (Xc) will be halved.

What is the reactance of a capacitor in a DC circuit?

In DC, the frequency is 0 Hz. According to the formula, dividing by zero results in infinity. Therefore, a capacitor has infinite reactance to DC once it is fully charged.