Nikola Tesla Books
IN SEARCH OF NIKOLA TESLA Being a smart child, the daughter uses the idea of resonance to send her little brother high into the air. By giving a series of small pushes, timed to coincide exactly with the natural oscillation of the swing, she is able to transfer energy from her arms into the swing. If the timing is not right, then the swing behaves in an erratic way, but if the pushes are 'in resonance', then each impulse adds progressively. The child goes higher and higher through the cumulative effects of a series of small pushes; in this way a large amount of energy can be transferred from the arms to the swing. In the same way, an opera singer will pitch her voice exactly to the natural vibrational frequency of a glass. By holding the note âin resonance' with the glass, energy is transferred. This transferred energy builds up to a point where the molecular structure of the glass is under such a stress that it disrupts and the glass shatters. Other examples of resonance are not hard to find: the sudden increase in clarity of a radio station as it is 'tuned in' or, in scientific terms, as the resonant frequency of the circuit in the receiver is brought into resonance with the broadcast signal. Soldiers who march across a suspension bridge, in step, are in danger of exciting one of the modes of vibration of the bridge if their rate of marching is in resonance with the swing of the bridge, so that the bridge begins to swing from side to side with increasing violence. Nikola Tesla had used this same 'habit of nature' in his invention of the coil which has been named after him. Making use of resonance in several stages of the device, he discovered a way of generating very high voltages and frequencies using ordinary household electric current and a device small enough to fit into the hand. A Tesla coil consists of three main circuits: A, B and C. Conventional energy, from a normal electric circuit, is brought in at A and the novel phenomenon of high-frequency and high-voltage discharge occurs at the spark in C. Conventional power, fed into A, finds itself on one side of a transformer. This transformer has the effect of 'stepping up' the voltage from A into the second circuit, B. 31
