Ham Radio General Class Practice Test

What effect does increasing the frequency of AC have on a capacitor's reactance?

1. The reactance decreases

2. The reactance increases

3. The amplitude increases

4. The amplitude decreases

The correct answer is: The reactance decreases

Increasing the frequency of alternating current (AC) has a specific effect on a capacitor's reactance, which is the measure of how much the capacitor resists the flow of AC. The formula for capacitive reactance (Xc) is given by: \[ Xc = \frac{1}{2\pi f C} \] where \( f \) is the frequency and \( C \) is the capacitance. According to this formula, as the frequency \( f \) increases, the denominator increases, resulting in a decrease in capacitive reactance. This relationship highlights that higher frequencies make it easier for AC to pass through the capacitor. Therefore, increasing the frequency reduces the reactance, allowing more current to flow. This fundamental concept is critical in understanding how capacitors operate in AC circuits, and it is particularly important for radio and other high-frequency applications in ham radio operations.