if you have a permanent magnet slotted into a laminated yoke like a transformer has. But this yoke has a telescopic piece which is made in the from of a bunch of wires running in line with the magnetic field . if this piece is pulled shut and open to increase and decrease the magnetic path resistance and there is a coil on the yoke and the increasing and decreasing magnetic flux creates electricity where does the energy for the electricity come from. I guess it comes from the phsyical force of moving the telespcopic piece but since this hopefully has little current in it is laminated to reduce eddy currents where does it get its' magnetic field from to resist movement. Can someone please explain this so I can stop thinking about it and get on with fixing my house.