Question

Explain in less than 4 brief sentences how a Tesla coil works. Add a sketch.

Answer 1

A Tesla coil consists of two parts: a primary coil and secondary coil, each with its own capacitor. (Capacitors store electrical energy just like batteries.) The two coils and capacitors are connected by a spark gap — a gap of air between two electrodes that generates the spark of electricity. An outside source hooked up to a transformer powers the whole system. Essentially, the Tesla coil is two open electric circuits connected to a spark gap. The power source is hooked up to the primary coil. The primary coil's capacitor acts like a sponge and soaks up the charge. The primary coil itself must be able to withstand the massive charge and huge surges of current, so the coil is usually made out of copper, a good conductor of electricity. Eventually, the capacitor builds up so much charge that it breaks down the air resistance in the spark gap. Then, similar to squeezing out a soaked sponge, the current flows out of the capacitor down the primary coil and creates a magnetic field. The massive amount of energy makes the magnetic field collapse quickly, and generates an electric current in the secondary coil. The voltage zipping through the air between the two coils creates sparks in the spark gap. The energy sloshes back and forth between the two coils several hundred times per second, and builds up in the secondary coil and capacitor. Eventually, the charge in the secondary capacitor gets so high that it breaks free in a spectacular burst of electric current. The resulting high-frequency voltage can illuminate fluorescent bulbs several feet away with no electrical wire connection. In a perfectly designed Tesla coil, when the secondary coil reaches its maximum charge, the whole process should start over again and the device should become self-sustaining. In practice, however, this does not happen. The heated air in the spark gap pulls some of the electricity away from the secondary coil and back into the gap, so eventually the Tesla coil will run out of energy. This is why the coil must be hooked up to an outside power supply.
The principle behind the Tesla coil is to achieve a phenomenon called resonance. This happens when the primary coil shoots the current into the secondary coil at just the right time to maximize the energy transferred into the secondary coil. Think of it as timing when to push someone on a swing in order to make it go as high as possible.