Electromagnetic interference (or EMI ) is a disruption that affects an electrical circuit because of either electromagnetic induction or externally emitted electromagnetic radiation. By understanding the source, the coupling methods and the susceptibility of the victim, the level of interference can be reduced to a level where the EMI causes no undue degradation in performance.
It’s caused when the changing electromagnetic fields generated by one cable induce extraneous currents or interference in adjacent or nearby cables. EMI is only a problem with copper cabling.
This is commonly observed in radios when switching between frequencies and static is hear as well as on over-the-air TV when the picture becomes distorted because the signal has been. These fields can cause problems in any electric device with a circuit board.




