Which component stores energy in a magnetic field?

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

Answer: (B)

Storing energy in a magnetic field is a property of the inductor. When current passes through the coil, a magnetic field builds around the winding and energy is stored in that magnetic field. The amount stored is proportional to the inductance and the square of the current, U = 1/2 L I^2, and this energy can be released back into the circuit as current changes, which is why inductors resist changes in current. Resistors mainly dissipate energy as heat and don’t store energy in a field. Capacitors store energy in an electric field between plates, not a magnetic field. Diodes don’t store energy in a magnetic field; they control current flow. So the component that stores energy in a magnetic field is the inductor.