Which device stores energy electrostatically in a circuit?

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

Answer: (C)

Capacitors store energy electrostatically in the electric field between their plates. When a capacitor is charged, positive and negative charges accumulate on opposite plates, creating a strong electric field in the dielectric between them. The energy stored in that field is given by the formula E = 1/2 C V^2, where C is the capacitance and V is the voltage across the plates. This storage is purely electric in nature, not magnetic.

In contrast, inductors store energy in a magnetic field around a conductor due to current flow, with energy = 1/2 L I^2. Resistors don’t store energy; they convert it to heat. Transformers rely on magnetic fields to transfer energy between windings, and while they involve energy storage in a magnetic field, that is not electrostatic storage.