Tesla coil

electrical resonant transformer circuit invented by Nikola Tesla

A Tesla coil is an electrical machine invented by Nikola Tesla in 1891. It is a radio-frequency oscillator and resonant transformer that generates high voltage electricity at low currents. One use is to make lightning bolts. Most are used nowadays to entertain. "Singing Tesla coils" have also been made that can create music.

Giant Tesla coil indicating millions of volts of electricity

It works on the principle of electromagnetic induction