Large Tesla coil. 15 inch discharge.

Large Tesla coil. 12 inch discharge. The Tesla Coil is a high frequency, weakly coupled, air-core transformer. Under ideal conditions, this demo is capable of producing 12 inch sparks. The first part of the apparatus is a 120 V.A.C., 60 Hz, step-up transformer that produces about 15,000 V.A.C at the secondary. The leads from the secondary are attached to either side of a spark gap. The spark gap is part of a series tank circuit containing a large, oil-filled capacitor (.02 _f, mica dielectric, rated at 20 kVolts) and the primary coil of the Tesla apparatus (10 turns, 27 _h). If the spark gap is set at about .25 inches, it will take about 2.5 kVolts to break down the air between the gap electrodes (10 kVolts/Inch on average). Thus, when the secondary of the transformer raises to 2.5 kVolts in the A.C. cycle (or lowers to - 2.5 kVolts), a spark will jump across the gap and the tank circuit will ring at its resonant frequency (about 217 kHz). The high frequency is important because the induced voltage in the Tesla secondary is proportional to the frequency of the primary coil signal (and to the square root of the ratio of the secondary winding inductance to the primary winding inductance). A spark of 12 inches means about 120 kV.A.C. NOTE: To tune the Tesla Coil properly, only about 8 turns of the primary are actually used. There are marked spots indicating where to clip the leads. Larger sparks can be produced if compressed air is sprayed through the spark gap, raising the voltage necessary to cause a spark to jump the gap. Also, the gap distance can be increased.