Reactance has some similarities with resistance and can be thought of in basic terms as resistance to alternating currents. This includes currents at radio frequencies.

### Capacitive Reactance

The impedance of a capacitor is given by the formula

- <math>Z = {1 \over j\omega C}</math>

Where <math>C</math> is the capacitance, <math>\omega</math> is <math>2 \pi f</math>, and <math>f</math> is the frequency. <math>j</math> is “operator j” from phasor analysis.

In prasctical terms this leads to:

<math> X_c = \frac {1} {2\pi F C} </math> where

- <math> X_c </math> is capacitive reactacnce
- F is the frequency of operation in Hertz
- C id the capacitance in Farads

### Inductive Reactance

The impedance of an inductor is given by the formula

- <math>Z = j \omega L \,</math>

where <math>Z\,</math> is the impedance, <math>\omega\,</math> is <math>2 \pi f\,</math>, and <math>f\,</math> is the frequency. <math>j\,</math> is “operator j” from phasor analysis.

In pracical terms this leads to:

<math> X_c = 2 \pi F L </math> where:

- <math> X_c </math> is capacitive reactance
- F is the frequency of operation in Hertz
- L is the inductance in Henries

## External links

- Reactance calculator from Electronics 2000