Which component stores energy in an electric field?

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

Answer: (C)

Energy storage in an electric field is what a capacitor does. A capacitor has two conducting plates with a dielectric in between; when a voltage is applied, charge builds up on the plates and creates an electric field across the gap. The energy sits in that electric field, and the amount of energy depends on the plates’ capacitance and the voltage (U = 1/2 C V^2). Resistors don’t store energy—they dissipate it as heat. Inductors and transformers store energy in magnetic fields around coils, not in electric fields. So the component that stores energy in an electric field is the capacitor.