In electronics 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.
The name comes from blocking—“choking”—high frequencies while passing low frequencies. It is a functional name; the name “choke” is used if an inductor is used for blocking or decoupling higher frequencies, but is just called an “inductor” if used in electronic filters or tuned circuits. Inductors designed for use as chokes are usually distinguished by not having the low loss construction (high Q factor) required in inductors used in tuned circuits and filtering applications.