I know that an iron coil channels and concentrates the magnetic flux of a coil inductor, but does an iron core increase the total energy capacity of the coil at peak current? The iron increases the inductance which should increase the energy capacity right? The energy takes longer to induce into the coil, but at the same peak current the inductor has now stored more energy right?


Yes, an iron core increases the inductance of a coil, and at any given exciting current, that also increases the stored energy.

Ferromagnetic materials (iron being the most familiar) do not merely channel the field, but take on polarization (which is effectively extra circulating current that does not go through the external electric circuit). That effect is not unlimited, because only a few electrons are free to take new spin and orbit alignment. Once you get to 100% alignment, the magnetic polarization response to additional current is zero.

This effect, 'saturation', sets a maximum current, above which a coil's inductance is no longer enhanced by the core. That complicates the claim that "at the same peak current the inductor has now stored more energy". Peaks of current might be excursions into saturation.

  • $\begingroup$ Thanks, @Whit3rd or anyone, Do you have an idea at steady state DC and not in AC operation, for reasonable dimensions, that you might find most commonly in ordinary electronic components, doorbells etc., what percent difference in stored energy would be reasonable to expect (high % and low %) between an air core and an iron core solonoid same dimensions and turns. $\endgroup$
    – DMac
    Nov 26 '17 at 1:30
  • $\begingroup$ Ratio of energy storage is the '(relative) magnetic susceptibility'. Magnetic susceptibility of iron (depending on strains and impurities and crystallization details) is in the thousands range: 200,000 is achievable but not practical, 4000 is a cheap transformer steel value. The designer will usually allow for smaller values than measured, to allow for saturation effects. $\endgroup$
    – Whit3rd
    Nov 26 '17 at 2:48

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