Tesla coil

A Tesla coil is a high-voltage air-core self-regenerative resonant transformer generating very high voltages at high frequency, named after its inventor Nikola Tesla. The Tesla coil achieves a great gain in voltage in a different way from a conventional transformer.

The primary and secondary coils make up an air-core transformer. Tesla coils are composed of two coupled LC circuits - The tank circuit is series LC circuit composed of the capacitor, spark gap, and primary coil; The second LC circuit, which is a series resonant circuit, is the secondary coil and the toroid. The toroid is one terminal of a capacitor, the other terminal being the ground.

In operation high-voltage sparks strike out in all directions from the toroid into the air.

In modified form, this type of transformer provides the voltage needed to power the cathode ray tube that makes (non-LCD) televisions and monitors possible.