Editing Magnetic core (section)

===== Silicon alloying =====
A small addition of [[silicon]] to iron (around 3%) results in a dramatic increase of the [[resistivity]] of the metal, up to four times higher.{{citation needed|date=August 2011}}  The higher resistivity reduces the eddy currents, so [[silicon steel]] is used in transformer cores. Further increase in silicon concentration impairs the steel's mechanical properties, causing difficulties for rolling due to brittleness.

Among the two types of [[silicon steel]], grain-oriented (GO) and grain non-oriented (GNO), GO is most desirable for magnetic cores. It is [[anisotropic]], offering better magnetic properties than GNO in one direction. As the magnetic field in inductor and transformer cores is always along the same direction, it is an advantage to use grain oriented steel in the preferred orientation. Rotating machines, where the direction of the magnetic field can change, gain no benefit from grain-oriented steel.