An inductor is a passive two-terminal electrical component that stores energy in its magnetic field. It generates a magnetic flux linkage when current flows through the conductor, and this ratio defines the inductance.
Heinrich Daniel Ruhmkorff invented the induction coil he named inductorium in 1851. Modern standardization eventually adopted the simpler name inductor for the component based on his work with these early devices.
An inductor usually consists of a coil of conducting material wrapped around a core either of plastic or of a ferromagnetic material. Insulated copper wire is the typical choice for the winding itself while soft ferrites are widely used for cores above audio frequencies.
At 6 MHz the skin depth of copper wire is about 0.001 inches or 25 micrometers so most of the current stays within this depth of the surface. The resistance of a wire to high frequency current is higher than its resistance to direct current because of skin effect.
Large inductors in power supplies remove ripple which is a multiple of the mains frequency from the direct current output. Inductors are also employed in electrical transmission systems where they limit switching currents and fault currents and are more commonly referred to as reactors in that field.