If you take a coil and make a current flow through it, the coil creates a magnetic field. This field induces a voltage into the coil that produces a counter current that weakens the primary current and voltage. If you then measure the voltage and current you can calculate the impedance of the coil.
My question now is, is the impedance higher before the self-inductance or lower ? In other words, how does a magnetic field influence the impedance of a coil ? The complex impedance Z equals u/i ( complex ) but does u and i decrease proportionally or does u or i get smaller faster and make the impedance increase/decrease ?