Which component stores energy in an electric field by accumulating charge?

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

Answer: (A)

Energy can be stored in an electric field when two conductors hold opposite charges across an insulating gap. This is exactly what a capacitor does. When a voltage source is connected, charges accumulate on the two plates, creating an electric field in the dielectric between them. The energy stored is given by the expression 1/2 C V^2, where C is the capacitance determined by plate area, separation, and the dielectric material.

The other components behave differently: an inductor stores energy in a magnetic field created by current through its windings; a resistor dissipates energy as heat rather than storing it; a diode mainly controls current flow and does not store significant energy in a field like a capacitor (aside from minor transient effects).