Nikola Tesla Books
CHAPTER THREE The Tesla coil is a device which is so commonplace to the scientist that I had always taken it for granted. As I looked through the advanced textbooks on electricity and magnetism I was unable to find a circuit diagram for the coil but when I turned to a more elementary compendium of physics I found what I had been looking for. As I sat at my desk, looking at the circuit diagram, I had the insight that the key to the Tesla coil is resonance. The importance of resonance had again cropped up in the papers I had looked at the previous evening. This idea of resonance, I was to discover, lies at the heart of many of Tesla's inventions and is the key to his experiments on broadcast power. Resonance is not so much a law of nature as a manner in which nature works. In a sense resonance is one of nature's habits, for it extends right across science from electricity to steam engines, from molecular dynamics to the tone of a musical instrument and from the rattle of a railway carriage to the tuning of a radio. All systems in nature have their own particular way of vibrating: for example, the swing of the pendulum in a grandfather clock, the notes on a violin, waves on a lake, vibrations of a tuning fork, oscillations of an electric circuit, signals from a pulsar. Resonance describes the way in which large quantities of energy can be exchanged between such systems when their vibrations coincide. As a simple example, think of a little boy on a swing who has not yet learned to âpump' his legs. His father sends him kicking and screaming high into the air with one hefty push. The child swings back and forth, then shouts for more as his father pushes him again. Now, suppose that father gets bored and wanders off to look at the ducks. The pushing is left to his young daughter who just doesn't have the same amount of muscle power. What can she do? 30
