Riess spiral
Pair of spiral conductors with metal balls at their ends
From Wikipedia, the free encyclopedia
Riess spirals, or Knochenhauer spirals, are a pair of spirally wound conductors with metal balls at their ends. Placing one above the other forms an induction coil. Heinrich Hertz used them in his discovery of radio waves.[1] They are named for German physicists Peter Theophil Riess and K. W. Knochenhaue.