Question
How does a capacitor react to AC?
Answer Options
- A) As the frequency of the applied AC increases, the reactance decreases
- B) As the frequency of the applied AC increases, the reactance increases
- C) As the amplitude of the applied AC increases, the reactance increases
- D) As the amplitude of the applied AC increases, the reactance decreases
Correct Answer: A
Explanation
A capacitor’s opposition to AC current (capacitive reactance, X_C) is inversely proportional to the frequency of the applied current. The formula for capacitive reactance is X_C = 1 / (2\pi f C), where f is the frequency and C is the capacitance.
This formula clearly shows that as the frequency of the applied AC increases, the reactance decreases. At a very high frequency, a capacitor acts almost like a short circuit (very low impedance), a property that makes capacitors useful in RF bypass and coupling circuits.
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