text: Ferrite beads are one of the simplest and least expensive interference filters to install on preexisting electronic cabling. For a simple ferrite ring, the wire is wrapped around the core through the center, typically five or seven times. Clamp-on cores are also available, which attach without wrapping the wire: this type of ferrite core is usually designed so that the wire passes only once through it. If the fit is not snug enough, the core can be secured with cable ties, or if the center is large enough, the cabling can loop through one or more times. (However, although each loop increases the impedance to high frequencies, it also shifts the frequency of the highest impedance to a lower frequency.) Small ferrite beads can be slipped over component leads to suppress parasitic oscillation.
  Surface-mount ferrite beads are available. Like any other surface-mount inductor, these are soldered into a gap in the printed circuit board trace. Inside the bead component, a coil of wire runs between layers of ferrite to form a multi-turn inductor around the high-permeability core.
  Theory of operation
  Ferrite beads are used as a passive low-pass filter by dissipating radio frequency (RF) energy as heat by design.
  Ideal inductors, on the other hand, have no resistance and hence do not dissipate energy as heat. Ideal inductors only have inductive reactance, which reduces the flow of high-frequency signals by returning some of their energy back towards the signal source (possibly reducing the amount of power drawn) rather than dissipating that energy as heat (as done by the resistance in ferrite beads). While an inductor's reactance may commonly be referred to simply as impedance, impedance generally can be any combination of resistance and reactance.