How does a Tesla coil work? I have always been curious but never took the time to learn how to build one.
It's just a high frequency step up transformer. The spark gap, capacitor and primary form a resonant circuit. The large secondary provides the step up. It is common to excite the resonant primary with something like a neon transformer.
References concerning building Tesla coils
http://205.243.100.155/frames/build1.html