# LC reactance(calculation of LC reactance by each frequency)

It is troublesome to calculate the reactance ( impedance ) separately by each frequency when the capacitor and the coil are used. If an other value is understood, it is likely to be able to design easily. Next, I want to calculate these values beforehand.

## What is reactance?

The coil (inductance L) and the capacitor (capacitance C) show resistance different from direct current in the exchange. The value that corresponds to this resistance is called reactance (The unit is Ω) in the exchange. This reactance reaches a value different depending on frequency (f) of the exchange.

## Operation of CR series circuit(cutoff frequency of CR filter)

There is a thing that the circuit like the following comes out frequently with the capacitor and the coupling capacitor etc. of the CR filter in the electrical circuit. There is hesitating in good when the value of the capacitor is made which place at this time.

Generally, it is time when becoming a cutoff frequency is equal the impedance value of the capacitor and resistance. In this case, the output voltage decreases by 3dB.

I think that the value of the capacitor can often select this cutoff frequency to the standard, and the reactance table of the following capacitor becomes reference very much when the circuit is designed.

However, it is noted not to become it like this for the bypass capacitor of the emitter of a general amplifier.

## Reactance calculation value of capacitor  [Ω]

The reactance of capacitor C(impedance) in each frequency Zc is calculated by the following expression.

Zc = 1/(2πf C)

50Hz 60Hz 100Hz 300Hz 1kHz 3kHz 10kHz 100kHz 1MHz 10MHz 100MHz
10pF 318M 265M 159M 53.1M 15.9M 5.31M 1.59M 159k 15.9k 1.59k 159
100pF 31.8M 26.5M 15.9M 5.31M 1.59M 531k 159k 15.9k 1.59k 159 15.9
1000pF 3.18M 2.65M 1.59M 531k 159k 53.1k 15.9k 1.59k 159 15.9 1.59
0.01μF 318k 265k 159k 53.1k 15.9k 5.31k 1.59k 159 15.9 1.59 159m
0.1μF 31.8k 26.5k 15.9k 5.31k 1.59k 531 159 15.9 1.59 159m 15.9m
1μF 3.18k 2.65k 1.59k 531 159 53.1 15.9 1.59 159m 15.9m 1.59m
10μF 318 265 159 53.1 15.9 5.31 1.59 159m 15.9m 1.59m 159μ
100μF 31.8 26.5 15.9 5.31 1.59 531m 159m 15.9m 1.59m 159μ 15.9μ

It guarantees whether these values are neither calculation values to the last nor to actually become this value.

## Reactance calculation value of coil  [Ω]

The reactance of coil L(impedance) in each frequency ZL is calculated by the following expression.

ZL = 2πf L

50Hz 60Hz 100Hz 300Hz 1kHz 3kHz 10kHz 100kHz 1MHz 10MHz 100MHz
1μH 314μ 377μ 628μ 1.88m 6.28m 18.8m 62.8m 628m 6.28 62.8 628
10μH 3.14m 3.77m 6.28m 18.8m 62.8m 188m 628m 6.28 62.8 628 6.28k
100μH 31.4m 37.7m 62.8m 188m 628m 1.88 6.28 62.8 628 6.28k 62.8k
1mH 314m 377m 628m 1.88 6.28 18.8 62.8 628 6.28k 62.8k 628k
10mH 3.14 3.77 6.28 18.8 62.8 188 628 6.28k 62.8k 628k 6.28M
100mH 31.4 37.7 62.8 188 628 1.88k 6.28k 62.8k 628k 6.28M 62.8M
1H 314 377 628 1.88k 6.28k 18.8k 62.8k 628k 6.28M 62.8M 628M

It guarantees whether these values are neither calculation values to the last nor to actually become this value.