Tesla transformer

The Tesla coil is a resonant transformer for producing high voltage and high frequency alternating current, invented by Nikola Tesla in 1891. It consists of a primary and secondary coil, a capacitor, and a spark gap. When the capacitor in the primary circuit is charged and discharged through the coil, a high-frequency oscillation is created that induces a very high voltage in the secondary coil. Efficient energy transfer is achieved without an iron core, and spectacular sparks, light streaks, and luminescence in Geissler tubes can be seen at the output.