Nikola Tesla Books
CHAPTER VII. INDUCTION COIL OUTFITS OPERATED ON BATTERY CURRENT. Of all the experimental apparatus within the reach of the amateur builder, none can compare with the high potential, high frequency transformer when it comes to a question of demonstration or entertainment. A simple cardboard cylinder, wound with a few hundred turns of magnet wire in one layer, set on the top of the helix of his wireless set will give the experimenter a spark several inches long. This spark he can play with to his heart's content for it is perfectly harmless. Taken through a piece of metal held in the hand, the current produces no shock whatever even though the voltage may be expressed in the thousands. This is explained by the fact that the current changes its direction of flow so rapidly that the nerves cannot transmit the sensation of pain and the muscles cannot respond to the pulsations. Induction Coil Apparatus.-The experimenter who numbers among his possessions a spark coil suitable for radio telegraphy, may delve into the mysteries of high potentials, and high frequencies without spending any great amount of money for the extra apparatus needed. If he has the coil, he will most likely have also a spark gap and a high tension condenser. With this equipment to start off with, the experimenter will have only to add a simple Oudin resonator to his outfit 56
