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A ferrite bead – also called a ferrite block, ferrite core, ferrite ring, EMI filter, or ferrite choke [1] [2] – is a type of choke that suppresses high-frequency electronic noise in electronic circuits. Ferrite beads employ high-frequency current dissipation in a ferrite ceramic to build high-frequency noise suppression devices.
resistors: the braking resistors of electric trains, used to dissipate electrical power when the catenary is not receptive during braking, can make electromagnetically induced acoustic noise; coils: in magnetic resonance imaging, "coil noise" is that part of total system noise attributed to the receiving coil, due to its non-zero temperature.
The short terms "ferrite rod" or "loop-stick" sometimes refer to the coil-plus-ferrite combination that takes the place of both an external antenna and the radio's first tuned circuit or just the ferrite core itself (the cylindrical rod or flat ferrite slab). These broadcast ferrite rod aerials nearly always have a permeability of 125. [8]
A choke usually consists of a coil of insulated wire often wound on a magnetic core, although some consist of a doughnut-shaped ferrite bead strung on a wire. The choke's impedance increases with frequency. Its low electrical resistance passes both AC and DC with little power loss, but its reactance limits the amount of AC passed.
An electromagnetic coil is an electrical conductor such as a wire in the shape of a coil (spiral or helix). [ 1 ] [ 2 ] Electromagnetic coils are used in electrical engineering , in applications where electric currents interact with magnetic fields , in devices such as electric motors , generators , inductors , electromagnets , transformers ...
An electric current through a wire wound into a coil creates a magnetic field through the center of the coil, due to Ampere's circuital law. Coils are widely used in electronic components such as electromagnets, inductors, transformers, electric motors and generators. A coil without a magnetic core is called an "air core" coil.
A typical diameter of receiving loops with "air centers" is between 30 and 100 cm (1 and 3.5 feet). To increase the magnetic field in the loop and thus its efficiency, while greatly reducing size, the coil of wire is often wound around a ferrite rod magnetic core; this is called a ferrite loop antenna.
Electrical resonance occurs in an electric circuit at a particular resonant frequency when the impedances or admittances of circuit elements cancel each other. In some circuits, this happens when the impedance between the input and output of the circuit is almost zero and the transfer function is close to one.