Which component stores energy electrostatically in a circuit?

• A. Inductor
• B. Resistor
• C. Transformer
• D. Capacitor

Answer: (D)

A capacitor stores energy electrostatically in the electric field between its plates. When voltage is applied, charges accumulate on the plates, creating an electric field in the dielectric between them. The energy stored is proportional to the square of the voltage and the capacitance, described by the formula (1/2) C V^2. This stored energy can be released back into the circuit when the voltage changes, which is why capacitors are used for smoothing, filtering, and timing.

Resistors don’t store energy; they dissipate it as heat. Inductors and transformers store energy in magnetic fields created by current flowing through coils, not in electric fields. So the component that stores energy electrostatically is the capacitor.