A device that stores electrical energy in a magnetic field is a what?

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

Answer: (A)

Storing energy in a magnetic field comes from a coil carrying current, which is exactly what an inductor does. When current flows through a coil, it creates a magnetic field around it, and energy is stored in that field according to E = 1/2 L I^2, where L is the inductance. This stored magnetic energy makes inductors resist changes in current, a key behavior that underpins their use in filters, tuners, and energy storage in power supplies.

Capacitors store energy in an electric field between plates, not a magnetic field. Resistors convert electrical energy into heat and don’t store energy. Transformers use magnetic fields to transfer energy between circuits and to change voltage levels, but their primary described role isn’t energy storage—the inductor is.