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Why specifically do we use ferrites as the core for inductors? For example a NiZn toroid as a core for an inductor.

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  • \$\begingroup\$ Because they have a higher resistivity than metals and are cheaper than powder cores. \$\endgroup\$
    – Hearth
    Commented Apr 7, 2019 at 19:52
  • \$\begingroup\$ It wasn't obvious to me until I made some research, but I believe OP is talking about "Nickel-zinc ferrite", \$\text{Ni$_a$Zn$_{(1-a)}$Fe$_2$O$_4$}\$, (found here) and not Nickel-Zinc batteries. \$\endgroup\$ Commented Apr 7, 2019 at 19:56
  • \$\begingroup\$ What have you read so far? en.wikipedia.org/wiki/Ferrite_core and product.tdk.com/info/en/catalog/datasheets/… There are two material types and MANY variations of both. \$\endgroup\$ Commented Apr 7, 2019 at 20:02
  • \$\begingroup\$ Which other magnetic materials (and their electromagnetic properties) did you research before asking this question? \$\endgroup\$ Commented Apr 7, 2019 at 21:12
  • \$\begingroup\$ Hint: as mentioned by others, eddy effects are the main reason. Note how low-frequency AC inductors use laminated Si-steel cores, and then consider what happens as frequency increases. Ferrites are made of very small particles.sintered together. \$\endgroup\$ Commented Apr 8, 2019 at 2:26

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Permeability and saturation affect maximum field strength, operating current, and energy per pulse. Higher resistance/separation/layering of materials are used to reduce eddy current losses. The higher the frequency, the less inductance is necessary, so air core or PCB trace inductors see use in some applications. The promising sounding but potentially difficult to control resonant cuk converter may be able to operate at significant power levels with PCB trace inductors, even at low frequencies. If the factors of scale being talked about pan out, physical size of power converters could decrease by an order of magnitude. There are reasons to use ferrite(apparently high resistivity/permeability and low cost to manufacture), but it is far from the only material used. Each core material has a viable frequency range and energy density and when the goal is known, as it often is in engineering applications, it becomes as much a question of which type is necessary as of which type is best.

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