Which electrical component stores energy in an electric field?

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

Answer: (A)

Electric energy storage in a component comes from an electric field created by separated charges. A capacitor does this by two conductive plates with a dielectric between them; applying a voltage causes charges to accumulate on the plates, generating an electric field in the space between. The stored energy is W = 1/2 C V^2, with C depending on plate area, separation, and the dielectric. In contrast, an inductor stores energy in a magnetic field from current through a coil, a resistor simply dissipates energy as heat, and a transistor controls current rather than storing it in a field. So the capacitor is the element that stores energy in an electric field.