The Mighty 477 Blog

The Telsa coil needs a capacitor to store a charge and to form a resonant circuit with the primary coil in order to boost the frequency up (50,000 Hertz). After a failed attempt at using glass plates and aluminum foil, I discovered another "coiler" was using a salt water capacitor. The salt water, since it is conductive, acts like a plate in a capacitor, and the glass is the dielectric insulator between the two plates. One plate is in the bottle, and the other is the pool of saltwater outside the bottle. We used a copper pipe to bring the current to the capacitor. In later designs we used multiple smaller glass bottles because it increased the surface area of the capacitor thus making it larger. There are of course much more efficient designs, but we had limited time and money and it did serve it's purpose.