## Why does the resistance of an inductor increase when an iron core is introduced?

 Quote by yungman But R is the DC value only!!! Or are you implying the skin effect cause the R to go up and this has nothing to do with the inductance. It is pure resistance that increase with frequency!!! That actually makes sense!!! I think I answer my own question!!!
The theory of eddy current losses in transformer laminations is given in http://www.elect.mrt.ac.lk/EE201_em_theory.pdf
Page 7 shows that it increases as the square of frequency.

 Quote by jim hardy Yungman - check my thinking Iron losses in the core come out as heat so must cause an in-phase component of current. Else there'd be no net electrical energy transfer into core. P=VICos(Theta) and theta cant be 90 degrees if there's any watts heating the core. So they will appear to be another resistance in parallel which will show up as series in theveniin equivalent and the DC ohms will differ from the ohms in real component of complex Z. am i on track? old jim
I have no idea, till yesterday, the DC resistance was the only thing I consider. I am learning.
 Recognitions: Gold Member Science Advisor @ Bob S - what a great link that is. Interesting - hysteresis is to 1.6 power, same as Steinmetz measured ca 1890. My old 1901 Sylvanus Thompson book speaks of him in present tense. http://ieeexplore.ieee.org/Xplore/lo...hDecision=-203 Thanks !
 To say very simply and plainly... The Iron has drift current (because of earth's temperature) more than air. So, naturally more magnetic flux into it causes more aligned electrons with respect to the magnetic field applied. Magnetic flux is induced into it because inductor has twisted loops (Remember Biot-Sarvat Law which explains about the motion of electrons in a circular loop). Oriented electrons, formed in this manner, are always in a way that they oppose the flow of current through it - This is the basic principle of the inductor. Now as the no of electrons increase the total opposing flux through it increases (Self- induction) and so more opposition force followed by more impedance. Remarkably when you place a similar coil near the same inductive coil, the same voltage is generated in it, which we call as a transformer. A transformer doesn't work in very low voltages just like an inductor, because the thermally drifted electrons are absent. This is as simple as that. Make it more generalized than specialized. Hope you get it... :)

 Quote by jim hardy Yungman - check my thinking Iron losses in the core come out as heat so must cause an in-phase component of current. Else there'd be no net electrical energy transfer into core. P=VICos(Theta) and theta cant be 90 degrees if there's any watts heating the core. So they will appear to be another resistance in parallel which will show up as series in theveniin equivalent and the DC ohms will differ from the ohms in real component of complex Z. am i on track? old jim
I would agree that in order for heat to be generated the current would have to be in phase with the voltage. Would we look at this as a parallel resistance or a series one?