Here is a display of electrical forces that is more whimsical than profound. It may not add very much to our knowledge of physics. But I am fond of it.
A revolving Wimshurst machine, connected to two horizontal metal plates, produces an ever-changing charge on the plates, and thus a changing electric field in the space between them.
Between the plates are placed two lightweight figures made of pith, a cork-like substance. These mannequins are tiny, but they are elegantly dressed in fine 19th-century style.
When the machine is cranked, the puppets respond to the changing electric field between the plates by dancing. They hop up and down, alternately attracted and repelled by the nearby plates.
Any other small, light insulating objects would have served to illustrate this effect. But I think it’s charming to watch characters dressed for a ball do the dancing.
Wimshurst machines have many uses, and have played a supporting role in several Cabinet videos we have previously featured. I imagine that typically, in a classroom lecture, this simple demonstration would be one of several electrostatic experiments the lecturer would show.
The Foundation for Science and Technics, or Fondazione Scienza e Tecnica, of Florence, Italy, has made available many videos exploring the Cabinet of Physics, a large collection of antique scientific demonstration instruments. The Foundation’s homepage may be found here, and its Youtube channel, florencefst, here.