Inductors

What is an Inductor?

An inductor is basically a coil of conductive material (e. g. copper wire) wrapped around a core material.

Inductors store electrical energy in their magnetic field and release it when there is not enough energy to sustain that field.

Inductors block higher frequencies and will allow lower frequencies to pass, depending on their inductance.

They are typically used in power supplies as RF chokes/filters, loudspeaker crossovers as high frequency filters and in radio equipment(usually as parts of resonant circuits).

Coil Forms

Coil forms are simply objects to wind a coil around. Using a coil form allows you to wind air coils without trying to wind a coil onto air.

Core Materials

Ferrite - normally powdered iron to minimize circular currents
Wax - usually a sponge soaked in wax.
Air - least distortion, best for audio (too big for PSU filters, and generates stray inductance)
Resistor - Class B/AB amps usually have a 10-ohm resistor with a number of turns around it. Don't ask me, I don't know why (a hint for fellow editors).

Types

Solenoid - just a cylindrical coil of wire.
Toroid - wound on a ring-shaped core.