Nikola Tesla Books
Books written by or about Nikola Tesla
Colorado Springs
Oct. 5, 1899
Test of secondary last pattern, 17 turns in all.
To ascertain the period a spark gap adjustable was used in the secondary from end to earth, as usual, and the capacity and self-ind. of primary was varied until maximum spark length in secondary and other indications showed maximum resonant rise.
Results:
| Capacity in primary | Turns in self. box | } 1 turn primary (2 multiple) approximate |
|---|---|---|
| 7 tanks on each side | 13 " | |
| 8 " " | 10 " |
Now a ball 38.1 cm. was added on the end and placed near the earth plate at a distance of about 3 1/2 feet but very little affecting the vibration. This shows that distributed capacity in secondary is very large as before.
Capacity of one tank being 0.03816 mfd. Taking approx. Lp = 56,400 and 13 turns box 46,800
We have:
$! {T = {{2 \pi \over 1000} \sqrt{3.5 \times 0.03816 \times {103,200 \over 10^{9}}}} =} $!
$! {= {{2 \pi \over 1000} \sqrt{13.784 \over 10^{6}}} = {{2 \pi \over 10^{6}} \sqrt{13.784}} = {23.36 \over 10^{6}} = 0.00002336} $! and
n = 42,800 approx.
Some data to be preserved:
| Res. of cord used in measuring resistances: | 0.596 ohm |
| Res. of secondary 17 turns | 2.804 " |
| Res. of 2 primary t. in series | 0.004 " |
| Res. of Regulating self-ind. Coil | 0.054 " |
Coil wound for W.T. outfit.: Aug. 24, 1899
| Spool about 8 1/2" long: | 399 turns per layer | } |
| 22 layers |
Latest secondary in receiving apparatus, No. 30 wire, 90 turns per layer, 35 layers. Res. 424 ohms.
October 5
Tesla checks the secondary coil adjustment. The procedure is already standard. He adjusts the capacitance and inductance in the primary (with coil of variable inductance connected in series) until he achieves the maximum sparks at the secondary terminals. Operating frequency is approximately calculated on the basis of total inductance and capacitance in the primary. The influence of the secondary adjustment to oscillation is checked by a sphere addition of 38.1 cm in diameter and because that has very little influence he draws the conclusion that the distributed secondary capacitance is large.
The same day he continues the notes by writing about the sources of possible errors when determining the variances of globe capacitance with height variance. He give the precise interpolation form according to which method applied on Oct. 4, the desired capacitances variances can be found.
Starting from some height, he has to change the primary coil (by reconnecting the turns in series a connection) due to the small maximum capacitance value in the primary.
