As is known, {HEAD ~ a toroid magnet} is generally {TAIL ~ doughnut} shaped with a hole in the middle; one side is north, the other south 
As is known , { HEAD ~ a toroid magnet } is generally { TAIL ~ doughnut } shaped with a hole in the middle ; one side is north , the other south
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH