Hi, I heard it was possible if you symmetrically wind a toroid that you can get near total internal confinement of the magnetic field in the axial plane inside the toroid. How is this possible? I imagine a section of a closed loop of wire on the face of the toroid core, yet I still imagine those imaginary B lines around the wire like a circle at some arbitary radius passing through core and air half-half. Which can't be the case. Is there one of those pill-box or closed paths around a section explanations for how there is theoretically no B field in the air surrounding the toroid? Cheers!