structural:reformatting, information:classification
Magnetic core

The larger the current passed through the wire coil, the more the domains align, and the stronger the magnetic field is. Once all the domains are aligned, any additional current only causes a slight increase in the strength of the magnetic field. Eventually, the field strength levels off and becomes nearly constant, regardless of how much current is sent through the windings. This phenomenon is called saturation, and is the main nonlinear feature of ferromagnetic materials. For most high-permeability core steels, the maximum possible strength of the magnetic field is around 1.6 to 2 teslas (T). This is why the very strongest electromagnets, such as superconducting and very high current electromagnets, cannot use cores.