Tesla's Egg of Columbus
Nikola Tesla, at the 1893 World's Columbian Exposition, demonstrated a device he constructed known as the "Egg of Columbus." It was used to demonstrate and explain the principles of the rotating magnetic field model and the induction motor. Tesla's Egg of Columbus performed the feat of Columbus with a copper egg in a rotating magnetic field. The egg spins on its major axis, standing on end due to gyroscopic action.
Tesla's device used a toroidal iron core stator on which four coils were wound. The device was powered by a two-phase alternating current source (such as a variable speed alternator) to create the rotating magnetic field. The device operated on 25 to 300 hertz frequency. The ideal operating frequency was described as being between 35 and 40 hertz. Reproductions of the device are displayed at the Nikola Tesla Museum in Belgrade, the Memorial Centre "Nikola Tesla" in Smiljan, the Technical Museum in Zagreb, the Croatian History Museum in Zagreb and in the Ann Arbor Hands-On Museum.
- "Nikola Tesla's Egg of Columbus," including a photograph of the device in action. 21st Century Books.
- What Did Nikola Tesla Invent? - Tesla's Egg of Columbus Experiment