Hi Seb,
In response to your posts,
A coil of wire is inductive. It doesn't have a choice. As soon as the magnetic field starts to form the induction starts. (notice i said as the field starts to form)
Now if the 2 inductors were wound in a bifilar pattern together and connected to produce opposing magnetic fields you would have a net of 0 inductance, net meaning overall, but you still have circuit inductance. If they were set up to bolster each other i believe that you have 2x inductance minus 1/3 resistance, note that you need resistance to increase the magnetic field strength.
Electromagnets increase power with amp movement. if your circuit removed the amps then the inductance would be 0 regardless of how it was wound.
Something you should know about the term restrict, this term is also used with inductors in transmission and RF engineering. Basically what it says is the inductor acts like an ampere smoother. As more amps are passed through the inductor it creates a stronger magnetic field. As the magnetic field is created, it in turn increases the resistance, in turn increasing amp pull. This also works in reverse, once the field is set up if the amp supply drops some of the field collapses maintaining the amp flow out for a period of time equal to stored energy.
If you wound an inductor on a set magnetic core, what would happen is you have the effect of canceling/bolstering the magnetic field in the inductor to a point where the amp flow ceases and then as the field collapses it forces the charge to return to the previous state of magnetic orientation.
On this, there are High frequency devices that actually use strong reverse bias inductors as short burst diodes. As there is no required forward voltage in order to allow the flow of electrons.