A choke is an inductor used to block higher-frequency alternating current (AC) in an electrical circuit, while allowing lower frequency or DC current to pass. A choke usually consists of a coil of insulated wire often wound on a magnetic core, although some consist of a donut-shaped "bead" of ferrite material strung on a wire. The choke's impedance increases with frequency. Its low electrical resistance allows both AC and DC to pass with little power loss, but it can limit the amount of AC passing through it due to its reactance.

A line filter (EMI) is the kind of electronic filter that is placed between an electronic equipment and a line external to it, to attenuate conducted radio frequencies between the line and the equipment. 

A ferrite core is a type of magnetic core made of ferrite on which the windings of electric transformers and other wound components such as inductors are formed. It is used for its properties of high magnetic permeability coupled with low electrical conductivity.