A Tesla coil is an electrical resonant transformer device designed by inventor Nikola Tesla in 1891.

Originally, Tesla coils used fixed spark gaps or rotary spark gaps to provide intermittent excitation of the resonant circuit; more recently, electronic devices are used to provide the switching action required.

Operation

thumb|upright=1.3|Homemade Tesla coil in operation, showing [[brush discharges from the toroid. The high electric field causes the air around the high-voltage terminal to ionize and conduct electricity, allowing electricity to leak into the air in colorful corona discharges, brush discharges and streamer arcs. Tesla coils are used for entertainment at science museums and public events, and for special effects in movies and television.]]

thumb|Unipolar Tesla coil circuit. C2 is not an actual capacitor but represents the capacitance of the secondary windings L2, plus the capacitance to ground of the toroid electrode E.

A Tesla coil is a high-frequency, air-cored resonant transformer, which can be used to produce very high voltages. Elihu Thomson invented the Tesla coil circuit independently at the same time Tesla did.

Since they are simple enough for an amateur to make, Tesla coils are a popular student science fair project, and are homemade by a large worldwide community of hobbyists. Builders of Tesla coils as a hobby are called "coilers". They attend "coiling" conventions where they display their home-made Tesla coils and other high-voltage devices.

Tesla coils can also be used to generate sounds, including music, by modulating the system's effective "break rate" (i.e., the rate and duration of high power RF bursts) via MIDI data and a control unit. The actual MIDI data is interpreted by a microcontroller which converts the MIDI data into a PWM output which can be sent to the Tesla coil via a fiber optic interface. An extensive outdoor musical concert has demonstrated using Tesla coils during the Engineering Open House (EOH) at the University of Illinois Urbana-Champaign. The Icelandic artist Björk used a Tesla coil in her song "Thunderbolt" as the main instrument in the song. The musical group ArcAttack uses modulated Tesla coils and a man in a chain-link suit to play music.

Vacuum system leak detectors

Scientists working with high-vacuum systems test for the presence of tiny pin holes in the apparatus (especially a newly blown piece of glassware) using high-voltage discharges produced by a small handheld Tesla coil. When the system is evacuated the high-voltage electrode of the coil is played over the outside of the apparatus. At low pressures, air is more easily ionized and thus conducts electricity better than atmospheric-pressure air. Therefore, the discharge travels through any pin hole immediately below it, producing a corona discharge inside the evacuated space which illuminates the hole, indicating points that need to be annealed or reblown before they can be used in an experiment.

Teslaphoresis

In 2016, Rice University scientists used the field of a Tesla coil to remotely align tiny carbon nanotubes into a circuit, a process they dubbed "teslaphoresis".

Health issues<span class="anchor" id="RF_burn_anchor"></span>

thumb|Boy allowing an arc from a Tesla coil to strike his hand.

The high-voltage radio frequency (RF) discharges from the output terminal of a Tesla coil pose a unique hazard not found in other high-voltage equipment: when passed through the body, they often do not cause the painful sensation and muscle contraction of electric shock, as lower frequency currents do.

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Further reading

; Operation and other information

  • Armagnat, H., & Kenyon, O. A. (1908). The theory, design and construction of induction coils. New York: McGraw.
  • Haller, G. F., & Cunningham, E. T. (1910). The Tesla high frequency coil, its construction and uses. New York: D. Van Nostrand Co.
  • Iannini, R. E. (2003). Electronic gadgets for the evil genius: 21 build-it-yourself projects. TAB electronics. New York: McGraw-Hill. Pages 137–202.
  • Corum, Kenneth L. and James F. "Tesla Coils and the Failure of Lumped-Element Circuit Theory"
  • Nicholson, Paul, "Tesla Secondary Simulation Project" (Current state of the art in rigorously describing Tesla coil secondary behavior through theoretical analysis, simulation and testing of results in practice)
  • Vujovic, Ljubo, "Tesla Coil". Tesla Memorial Society of New York.
  • Hickman, Bert, "Tesla Coil Information Center"
  • Cooper, John. F., "Magnifying Transmitter early-type circuit diagram; Later-type circuit diagram". Tesla-Coil.com

; Electrical World

; Other publications

  • Corum, J. F., and K. L. Corum, "RF Coils, Helical Resonators and Voltage Magnification by Coherent Spatial Modes". IEEE, 2001.
  • de Queiroz, Antonio Carlos M., "Synthesis of Multiple Resonance Networks". Universidade Federal do Rio de Janeiro, Brazil. EE/COPE.
  • Haller, George Francis, and Elmer Tiling Cunningham, "The Tesla high frequency coil, its construction and uses". New York, D. Van Nostrand company, 1910.
  • Norrie, H. S., "Induction Coils: How to make, use, and repair them". Norman H. Schneider, 1907, New York. 4th edition.
  • Reed, J. L., "Tuning the triple resonance Tesla pulse transformer"
  • Curtis, Thomas Stanley, High Frequency Apparatus: Its Construction and Practical Application. Everyday Mechanics Co., 1916.
  • numerous academic IEEE publications [https://ieeexplore.ieee.org/search/searchresult.jsp?newsearch=true&queryText=tesla%20transformer]

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