<Tr> <Th> Inventor </Th> <Td> Nikola Tesla </Td> </Tr> <Tr> <Th> Related items </Th> <Td> Transformer, electromagnetic field, resonance </Td> </Tr> <P> The Tesla coil is an electrical resonant transformer circuit designed by inventor Nikola Tesla in 1891 . It is used to produce high - voltage, low - current, high frequency alternating - current electricity . Tesla experimented with a number of different configurations consisting of two, or sometimes three, coupled resonant electric circuits . </P> <P> Tesla used these circuits to conduct innovative experiments in electrical lighting, phosphorescence, X-ray generation, high frequency alternating current phenomena, electrotherapy, and the transmission of electrical energy without wires . Tesla coil circuits were used commercially in sparkgap radio transmitters for wireless telegraphy until the 1920s, and in medical equipment such as electrotherapy and violet ray devices . Today their main use is for entertainment and educational displays, although small coils are still used today as leak detectors for high vacuum systems . </P>

What is the purpose of a tesla coil