Post History

Inductance is defined by the shape of the coil, the area of the coil, the number of turns in the coil, the distance between turns, the ferromagnetic permeability of material within (and surrounding) the coil and induction to other not-so-obvious conducting parts.

Frequency lowering (with a fixed AC voltage) will produce more current and this can saturate magnetic permeable materials and this can lower inductance (sometimes quite considerably). Raising frequency beyond a point will cause some ferromagnetic materials to reduce their permeability and this will effectively lower inductance.