Capacitive Voltage Divider


Capacitive reactance


Capacitive reactance in a purely capacitive circuit is the counterforce to current flow only in AC circuits. Like the resistance, the reactance is measured in ohms, but receives the symbol X to distinguish it from a purely ohmic value. Since reactance is a quantity that has both inductors and capacitors, it is referred to as capacitive reactance in connection with capacitors. For capacitors in AC circuits, the capacitive reactance is indicated by the symbol XC. Then we can actually say that the capacitive reactance is a resistance that varies with frequency. The capacitive reactance also depends on the capacitance of the capacitor in Farads and the frequency of the AC waveform and the formula for defining the capacitive reactance:

Cx = 1 / 2 * pi * frequency * capacity


The capacitive reactance of the capacitor decreases with increasing frequency, therefore, the capacitive reactance is inversely proportional to the frequency.

Counteracting the current flow, the electrostatic charge on the plates (their AC capacitance value) remains constant, as it becomes easier for the capacitor to completely absorb the charge change on its plates during each half cycle.

Also, as the frequency increases, the current flowing through the capacitor increases as the rate of voltage change across its plates increases.

So we see that at dc, a capacitor has an infinite reactance (open circuit), at very high frequencies a capacitor has no reactance (short circuit).



Calculator


Input Voltage:   Volt
C1:   uF  nF 
C2:   uF  nF 
Frequency:   Hz


Start Frequency: 10 Hz
Stop Frequency: 25000 Hz
 





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