Inductors, coils and chokes are passive devices that are designed to resist changes in current and store energy in the form of a magnetic field. In their simplest form, inductors consist of a wire loop or coil. The inductance is directly proportional to the number of turns in the coil. Inductance also depends on the radius of the coil and on the type of material around which the coil is wound. With inductors, coils and chokes, air cores result in the least inductance for a given coil radius and number of terms.
What to Consider When Choosing?
Important specifications to consider when searching for inductors, coils and chokes include mounting options, core materials, lead types, and inductance types. Mounting options include through-hole and surface-mount technologies. Coils can be wound on various core materials.
The most popular are iron (or iron alloys, laminations, or powder); and ferrite, a black, nonconductive, brittle magnetic material. The use of these materials is designed to multiply the inductance of a given coil by the "permeability" of the core material. Other core materials include air, ceramic, and phenolic.
Lead types can be axial, radial, flying, no leads (SMT), tab, gull wing, and J-leads. With inductors, coils and chokes, the inductance can be fixed or variable.