Which statement about capacitors is true?

• A. Converts heat to electricity
• B. Dissipates energy as light
• C. Emits photons when charged
• D. Stores energy in an electric field

Answer: (D)

Capacitors store energy in the electric field between two conductive plates separated by a dielectric. When a voltage is applied, charges accumulate on the plates and create a field in that space, which is where the energy is held. The amount of energy stored is 1/2 times the capacitance times the square of the voltage (E = 1/2 C V^2). This stored energy is how a capacitor can supply current when the circuit changes, such as helping start a motor or smoothing voltage in a circuit. The other statements describe processes that aren’t how capacitors function; they don’t convert heat to electricity, dissipate energy as light, or emit photons simply because they’re charged.