The impedance of an alternating current (AC) circuit increases with frequency as a result of the contributions from capacitance and inductance.

As the frequency of an AC circuit rises, the reactance of both the capacitors and inductors within the circuit also increases. This leads to an overall increase in the circuit’s impedance.

For capacitors, the impedance is lower at lower frequencies. However, as the frequency increases, the capacitive reactance, denoted as $X_C$, is given by the formula:

where $f$ is the frequency and $C$ is the capacitance. Consequently, as frequency increases, the capacitive reactance decreases, meaning the capacitor becomes less effective at allowing current to pass through, thereby increasing its overall impedance.

Conversely, inductors exhibit higher impedance at lower frequencies. As the frequency increases, the inductive reactance, denoted as $X_L$, is defined by the formula:

where $L$ is the inductance. This means that as frequency increases, the inductive reactance also increases, making the inductor more resistive and contributing to an increase in its impedance.

The cumulative effect of these changes in impedance results in a circuit that becomes progressively more challenging for current to flow through as the frequency escalates. This phenomenon has significant implications for practical applications, particularly in the design of filters for electronic circuits.

In conclusion, the impedance of an AC circuit rises with frequency due to the effects of capacitance and inductance. This characteristic is essential to consider in electronic circuit design, as it influences the behavior and performance of various components.