If we rotate a spiral shaped tube the liquid is either pushed to the outside or the inside. Lets assume we do both and connect the input to the output of the 2 spirals.
The inwards spiraling force can not overpower the outwards spiral and the outwards spiral can not overpower the inwards one.
We now cheat this balance by using gravity to assist one of the spirals. There is extra pressure on the fluid on the downwards loop AND there is a vacuum in the center at the top.
This image represents a cone spiraled in and downwards on the outside, upwards in the inner tube and outwards on the top (not drawn).
So, after the liquid is pushed outwards increasing the spin1 the liquid spins downwards increasing the spin2.
Then the liquid is sucked up the tube from the vacuum at the top.
The liquid continues to spin and continues to increase the spin3.
It it sucked to the outside centrifugally and ..... I think you can guess the rest of this story.
Now we put ferrofluid in the core put our copper windings around it and use a magnet in stead of gravity.