5 Things to Know About Tesla Coils

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Tesla coils are resonant transformers invented by Nikola Tesla to conduct experiments using high alternating voltage. Some of these were in the fields of electrical lighting, wireless transmission of electric energy, X-ray generation etc.

What is Tesla Coil

Tesla coil is an induction coil for producing high-frequency alternating currents. Induction coil is a coil used to produce sporadic high voltage from a direct current. Tesla coil has loosely wound electrical wire around an iron or air core. The complete setup has two coil circuits, primary and secondary, placed some distance apart. The primary circuit uses DC input to generate high voltage current in the primary coil. Tesla coils produce a short spark gap to induce electric current to flow to the coil of the secondary circuit through air. This circuit in turn produces high frequency AC output.

Tesla Coil

Tesla Coil

Image Courtesy: http://www.teslacoildesign.com

History of Tesla Coils

Tesla coil was patented by Nikola Tesla in 1891. The visual effect of spark gaps made the coils popular. Tesla coils are often made and used by enthusiasts to produce long sparks for demonstration purposes. Nikola Tesla modified his own design in 1902 to prevent generation of sparks and used it for his advanced magnifying transmitters. He also introduced the concept of air-core coils instead of iron-core.

Modern Tesla Coils

Modern day Tesla coils use transistors or vacuum tubes instead of spark gap to generate power for the primary circuit. They come in two varieties: Solid-state Tesla coils and Dual Resonant Solid-state Tesla coils. Solid-state Tesla coils use transistors, MOSFETs or IGBTs for switching power between the two circuits. Dual Resonant solid-state Tesla coils use a combination of solid-state Tesla coils with spark gap Tesla coils.


Tesla coils were used for wireless telegraphy, radio transmitters and early models of televisions. However, they have been replaced by modern systems now. Sparks produced by Tesla coils continue to be used as spark plugs in vehicles to initiate fuel combustion. They are also used in electrical equipment to prevent generation of dangerous voltage spikes.

Safety Measures

The electric field generated by the Tesla coils can interfere with the functioning of electronic devices around them. Also, the heat produced by the Tesla coils expands air around them, ionized them and can even generate dangerous gases like Ozone and NO2. However, all these can be taken care of by operating Tesla Coils in open air or a sufficiently big and airy room.

Related Posts:

Nikola Tesla: Great Genius of Our Time

Alternating Voltage

Understanding Inductance


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