The circuit shown in Figure 218 is the one which should be followed in wiring the set. The wires which connect the various instruments should be passed through holes and along the under side of the base so that they are concealed.
HOW TO BUILD A TESLA HIGH-FREQUENCY COIL
A Tesla high-frequency coil or transformer opens a field of wonderful possibilities for the amateur experimenter. Innumerable weird and fascinating experiments can be performed with its aid.
When a Leyden jar or a condenser discharges through a coil of wire, the spark which can be seen does not consist simply of a single spark passing in one direction, as it appears to the eye, but in reality is a number of separate sparks alternately passing in opposite directions. They move so rapidly that the eye is unable to distinguish them. The time during which the spark appears to pass may only be a fraction of a second, but during that short period the current may have oscillated back and forth several thousand times.
If the discharge from such a Leyden jar or a condenser is passed through a coil of wire acting as a primary, and the primary is provided with a secondary coil containing a larger number of turns, the secondary will produce a peculiar current known as high-frequency electricity. High-frequency currents reverse their direction of flow or alternate from one hundred thousand to one million times a second.
Fig. 317.—Illustrating the Principle of the Tesla Coil. A Leyden Jar discharges through the Primary Coil and a High-Frequency Spark is produced at the Secondary.
High-frequency currents possess many curious properties. They travel only on the surface of wires and conductors. A hollow tube is just as good a conductor for high-frequency currents as a solid rod of the same diameter. High-frequency currents do not produce a shock. If you hold a piece of metal in your hand you can take the shock from a high-frequency coil throwing a spark two or three feet long with scarcely any sensation save that of a slight warmth.
The Tesla coil described below is of a size best adapted for use with a two-inch or three-inch spark coil, or a small high-potential wireless transformer. The purpose of the spark coil or the transformer is to charge the Leyden jars or condenser which discharge through the primary of the Tesla coil.
