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Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction. [1]
Electromagnetic compatibility (EMC) is the ability of electrical equipment and systems to function acceptably in their electromagnetic environment, by limiting the unintentional generation, propagation and reception of electromagnetic energy which may cause unwanted effects such as electromagnetic interference (EMI) or even physical damage to ...
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.
Electromagnetic shielding cages inside a disassembled mobile phone.. In electrical engineering, electromagnetic shielding is the practice of reducing or redirecting the electromagnetic field (EMF) in a space with barriers made of conductive or magnetic materials.
If circuit 2 is an audio system and circuit 1 has large AC currents flowing in it, the interference may be heard as a 50 or 60 Hz hum in the speakers. Also, both circuits have voltage on their grounded parts that may be exposed to contact, possibly presenting a shock hazard. This is true even if circuit 2 is turned off.
Different types of noise are generated by different devices and different processes. Thermal noise is unavoidable at non-zero temperature (see fluctuation-dissipation theorem), while other types depend mostly on device type (such as shot noise, [1] [3] which needs a steep potential barrier) or manufacturing quality and semiconductor defects, such as conductance fluctuations, including 1/f noise.
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.
In electrical circuits sharing a common signal return path, electrical impedance in the return path creates common impedance coupling between the signals, resulting in crosstalk. [1] [2] Crosstalk is a significant issue in structured cabling, audio electronics, integrated circuit design, wireless communication and other communications systems.