Editing Magnetic core (section)

==== Soft iron ====

"Soft" ([[annealing (metallurgy)|annealed]]) [[iron]] is used in magnetic assemblies, [[direct current]] (DC) electromagnets and in some electric motors; and it can create a concentrated field that is as much as 50,000 times more intense than an air core.<ref>{{cite web|url=http://www.physicsforums.com/archive/index.php/t-164613.html|title=Soft iron core}}</ref>

Iron is desirable to make magnetic cores, as it can withstand high levels of [[magnetic field]] without [[Saturation (magnetic)|saturating]] (up to 2.16 [[Tesla (unit)|tesla]]s at ambient temperature.<ref>Daniel Sadarnac, ''Les composants magnétiques de l'électronique de puissance'', cours de Supélec, mars 2001 [in french]</ref><ref>{{Cite journal|last1=Danan|first1=H.|last2=Herr|first2=A.|last3=Meyer|first3=A.J.P.|date=1968-02-01|title=New Determinations of the Saturation Magnetization of Nickel and Iron|journal=Journal of Applied Physics|volume=39|issue=2|pages=669–70|doi=10.1063/1.2163571|issn=0021-8979|bibcode=1968JAP....39..669D|doi-access=free}}</ref>)  Annealed iron is used because, unlike "hard" iron, it has low [[coercivity]] and so does not remain magnetised when the field is removed, which is often important in applications where the magnetic field is required to be repeatedly switched.

Due to the electrical conductivity of the metal, when a solid one-piece metal core is used in [[alternating current]] (AC) applications such as transformers and inductors, the changing magnetic field induces large [[eddy current]]s circulating within it, closed loops of electric current in planes perpendicular to the field.  The current flowing through the resistance of the metal heats it by [[Joule heating]], causing significant power losses.  Therefore, solid iron cores are not used in transformers or inductors, they are replaced by [[lamination|laminated]] or powdered iron cores, or nonconductive cores like [[ferrite (magnet)|ferrite]].