Nikola Tesla: Colorado Springs Notes, 1899-1900 Page 317

These data enable us to determine how many turns are to be left off on bottom of coil in order that it be in resonance with the primary exciting system under the best working conditions of the latter; the structure being connected to the coil.

Now the secondary, to be at best, should work with all jars available and the regulating coil should be all cut out in the primary. This is namely the condition corresponding to full output and highest economy. Under such working conditions the secondary will modify greatly the inductance of the primary and for the present approximate estimate it will be close enough to assume a diminution of about 50% of the primary inductance so that the latter may be put at 28,000 cm. This would then give in Test 2:

But capacity in primary with all jars as would be required for best working would be $! {{8 \times 36} \over 2} $! = 144 bottles = 0.1296 mfd. Reduced to this capacity the inductance in primary would have been in reading 2. instead of 45,300 cm only $! {0.0648 \over 0.1296} $! x 45,300 = 22,650 cm.

Taking now reading 1. when structure was connected to the free terminal of coil the inductance in primary was 20 3/8 turns + conn. = 72,660 cm from table. But in this case the capacity was 0.13759 mfd. Reducing this to the capacity when secondary works best, that is, to 0.1296 mfd the inductance with this capacity would have been larger by a ratio of $! {0.13759 \over 0.1296} $! = 1.048 or it would have been 72,660 x 1.048 = 76,150 cm, approx. Thus we have the following data:

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