Ham Amateur Radio Technician Practice Exam 2026 – The Complete All-in-One Guide to Exam Success

A capacitor's behavior in an alternating current (AC) circuit is determined by its reactance, which is the opposition it offers to the flow of AC. Reactance is influenced by the frequency of the AC signal and the capacitance value of the capacitor itself.

As the frequency of the AC signal increases, the capacitive reactance decreases according to the formula:

\[ X_C = \frac{1}{2\pi f C} \]

where \( X_C \) is the reactance in ohms, \( f \) is the frequency in hertz, and \( C \) is the capacitance in farads. From this relationship, it's clear that when the frequency \( f \) rises, \( X_C \) becomes smaller, indicating decreased reactance.

This property of capacitors allows them to easily pass higher frequency AC signals while impeding lower frequency signals. Thus, in AC circuits, capacitors can effectively act as frequency filters, allowing higher frequencies to pass through while blocking lower frequencies. This characteristic is particularly utilized in various applications, including tuning circuits and signal processing.

The other choices do not align with the fundamental behavior of capacitors in AC circuits and omit this critical inverse relationship between frequency and reactance.