A ferrite core is a kind of magnetic core made of ferrite and on which the windings of electric transformers and other wound components including inductors are formed. It is used to prevent eddy currents because of its properties of high magnetic permeability and low electrical conductivity. Ferrite cores are ceramic magnetic bodies that consist of soft ferrites formed into various shapes.
Examples of common soft ferrites include manganese-zinc ferrite and nickel-zinc ferrite depending on the composition. Mn-Zn ferrite is highly conductive and has to be insulated, whereas Ni-Zn ferrite has higher frequency, making it appropriate for use in noise countermeasures. Application of ferrite cores is based on their sizes. The signal transformers are small in size with relatively high frequencies. On the other hand, power transformers are larger in size with lower frequencies. Based on their shapes, ferrite cores can be classified as toroidal cores, cylindrical cores and shell cores.
Ferrite rod aerials, which are a type of Small Magnetic Loop (SML) antennae, are popular in broadcast band transistor radios. They are also common in VFL receivers and can work well over most of the shortwave frequencies when used with an appropriate ferrite. The ferrite used for signals serve a range of applications ranging from 1 kHz to several MHz.