A Tesla coil is an electrical resonant transformer circuit invented by Nikola Tesla around 1891. It is used to produce high-voltage, low-current, high frequency alternating-current electricity. Tesla coils produce higher current than the other source of high-voltage discharges, electrostatic machines. Tesla experimented with a number of different configurations and they consist of two, or sometimes three, coupled resonant electric circuits.
Mark Twain in Nikola Tesla's apartment, New York 1894 The high-voltage current is being passed through the human body to bring the lamp to incandescence. Tesla's friend, Mark Twain, is holding the loop above the resonating coil. Tesla is in the background. Originally published as part of an article by T.C. Martin called "Tesla's Oscillator and Other Inventions" that appeared in the Century Magazine (April 1895)
The "majestic luminous column" that illuminated the Electrical Building at the Chicago World's Fair, 1893. The structure included thousands of incandescent light bulbs. Westinghouse Corp. lit the Fair, using Nikola Tesla's invention of alternating current.