Nikola Tesla

Nikola Tesla

Nikola Tesla was a Serbian-American inventor, mechanical engineer, and electrical engineer...

, at the 1893 World's Columbian Exposition

World's Columbian Exposition

The World's Columbian Exposition was a World's Fair held in Chicago in 1893 to celebrate the 400th anniversary of Christopher Columbus's arrival in the New World in 1492. Chicago bested New York City; Washington, D.C.; and St...

, demonstrated a device he constructed known as the "Egg of Columbus

Egg of Columbus

An egg of Columbus or Columbus's egg refers to a brilliant idea or discovery that seems simple or easy after the fact. The expression refers to a popular story of how Christopher Columbus, having been told that discovering the Americas was no great accomplishment, challenged his critics to make an...

." It was used to demonstrate and explain the principles of the rotating magnetic field

Rotating magnetic field

A rotating magnetic field is a magnetic field which changes direction at a constant angular rate. This is a key principle in the operation of the alternating-current motor. Nikola Tesla claimed in his autobiography that he identified the concept of the rotating magnetic field in 1882. In 1885,...

 model and the induction motor

Induction motor

An induction or asynchronous motor is a type of AC motor where power is supplied to the rotor by means of electromagnetic induction. These motors are widely used in industrial drives, particularly polyphase induction motors, because they are robust and have no brushes...

. Tesla's Egg of Columbus performed the feat of Columbus

Egg of Columbus

An egg of Columbus or Columbus's egg refers to a brilliant idea or discovery that seems simple or easy after the fact. The expression refers to a popular story of how Christopher Columbus, having been told that discovering the Americas was no great accomplishment, challenged his critics to make an...

 with a copper

Copper

Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

 egg in a rotating magnetic field

Magnetic field

A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...

. The egg spins on its major axis, standing on end due to gyroscopic action.

Tesla's device used a toroid

Toroid

Toroid may refer to*Toroid , a doughnut-like solid whose surface is a torus.*Toroidal inductors and transformers which have wire windings on circular ring shaped magnetic cores.*Vortex ring, a toroidal flow in fluid mechanics....

al iron

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 core stator

Stator

The stator is the stationary part of a rotor system, found in an electric generator, electric motor and biological rotors.Depending on the configuration of a spinning electromotive device the stator may act as the field magnet, interacting with the armature to create motion, or it may act as the...

 on which four coil

Coil

A coil is a series of loops. A coiled coil is a structure in which the coil itself is in turn also looping.-Electromagnetic coils:An electromagnetic coil is formed when a conductor is wound around a core or form to create an inductor or electromagnet...

s were wound. The device was powered by a two-phase alternating current

Alternating current

In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....

 source (such as a variable speed alternator

Alternator

An alternator is an electromechanical device that converts mechanical energy to electrical energy in the form of alternating current.Most alternators use a rotating magnetic field but linear alternators are occasionally used...

) to create the rotating magnetic field. The device operated on 25 to 300 hertz

Hertz

The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....

 frequency. The ideal operating frequency was described as being between 35 to 40 hertz. Reproductions of the device are displayed at the Nikola Tesla Museum

Nikola Tesla Museum

The Nikola Tesla Museum is located in the central area of Belgrade. It holds more than 160,000 original documents, over 2,000 books and journals, over 1,200 historical technical exhibits, over 1,500 photographs and photo plates of original, technical objects, instruments and apparatus, and over...

 in Belgrade, the Technical Museum

Technical Museum, Zagreb

Technical Museum is located at 18 Savska Street in Zagreb and it exhibits numerous historic aircraft, cars, machinery and equipment.-The Museum features:...

 in Zagreb

Zagreb

Zagreb is the capital and the largest city of the Republic of Croatia. It is in the northwest of the country, along the Sava river, at the southern slopes of the Medvednica mountain. Zagreb lies at an elevation of approximately above sea level. According to the last official census, Zagreb's city...

 and in the Ann Arbor Hands-On Museum

Ann Arbor Hands-On Museum

Ann Arbor Hands-On Museum located in Ann Arbor, Michigan, USA, specializes in interactive exhibits.The Ann Arbor Hands-On Museum was founded in 1978, with approval from the city of Ann Arbor, as a touring collection of exhibits built by local specialists and volunteers...

.

External links

• What Did Nikola Tesla Invent? - Tesla's Egg of Columbus Experiment