One of the main applications of a Capacitance is to

A capacitor passes AC signals and blocks DC signals.

This can be understood with the help of the reactance formula.

The capacitive reactance is given by:

\(X_C=\frac{1}{\omega C}=\frac{1}{2\pi fC}\)

f = frequency of the voltage/current applied across the capacitor.

C = Capacitance value

For DC:

A DC signal is a zero frequency signal, i.e. f = 0 Hz

X_C for f = 0 will be:

\(X_C=\frac{1}{2\pi (0)C}= \infty \)

For AC:

AC signal is a signal having a particular frequency 'f',

X_C for any frequency f is given by:

\(X_C=\frac{1}{2\pi fC}= Finite\)

Observation:

• For DC we conclude that a capacitor provides infinite resistance to the flow of current. Hence no current will flow as current in a capacitive circuit is given by:

          \(I=\frac{V}{X_C}\)

• For AC we observe that the resistance offered by the capacitor is finite. Hence a finite flow of current is possible in a capacitive circuit with AC input.