An inductor is defined as what?

• A. A coil of wire that stores energy in a magnetic field
• B. A device that dissipates energy as heat
• C. A capacitor that stores energy electrostatically
• D. A resistor that limits current

Answer: (A)

An inductor is a coil of wire that stores energy in a magnetic field created by current flowing through it. The energy stored grows with the inductance and the current, described by W = 1/2 L I^2. This magnetic energy storage is what gives an inductor its behavior of opposing changes in current, since a changing current induces an emf that tries to keep the current steady (V = L di/dt). It doesn’t dissipate energy as heat like a resistor, and it isn’t a capacitor, which stores energy in an electric field.