How is the reactance of a capacitor at a given frequency calculated?

• A. Using R = V/I formula
• B. Using Xc = 1 / (2πfC) formula
• C. Using P = VI formula
• D. Using L = μ/ (2πf) formula

Answer: (B)

The reactance of a capacitor, denoted as Xc, is calculated using the formula Xc = 1 / (2πfC). This formula illustrates the relationship between the reactance of the capacitor, the frequency of the AC signal (f), and the capacitance (C).

Reactance is a measure of how a capacitor impedes the flow of alternating current (AC) due to its ability to store and release energy in an electric field. As frequency increases, the reactance decreases, showing that capacitors allow more AC to pass through at higher frequencies. Conversely, a higher capacitance value results in lower reactance, further facilitating current flow.

The other choices pertain to different electrical concepts that do not apply to calculating capacitor reactance. The formula involving R = V/I relates to resistance in ohmic materials, while P = VI computes power in an electrical circuit. The L = μ / (2πf) formula is related to inductive reactance and not relevant to capacitive calculations. This understanding of the correct formula connects directly to capacitor behavior in AC circuits, which is essential for analyzing and designing electrical systems.