Nikola Tesla Books
Books written by or about Nikola Tesla
Tests showed best result with 56 - 68 primary turns. 62 turns, No. 20 cord, are now used. Res. of cord 0.39 ohm.
Test with special coil for determining more accurately the law of variation of capacity with elevation. The coil with 400 turns No. 20 cord was used as previously and the adjustable ball of 38.1 cm capacity. The ball was normally above the extra coil repeatedly referred to, which on account of its great internal capacity was not used. Although unconnected some error was necessarily caused by the presence of the coil near the ball when the latter was near its lowest position.
A further error was anticipated from the influence of the roof at the points when the ball, which was being gradually lifted during the test, was nearest to it. The smallest distance or nearest point was about 11 feet. Nevertheless some action was bound to occur although the wood is very dry here and it is proposed in later tests to eliminate these errors as much as possible. The roof was covered with some sort of tar paper the influence of which can only be conjectured at present. The most reliable data will be those obtained with ball at the highest points when it is above all structures. The connections used are shown in diagram.
The ball was lifted by steps of one foot each and the primary self-induction and capacity was adjusted until maximum resonant rise was observed on special coil, and adjustable secondary spark gap serving as analizer, besides streamers which served even as a better guide. The results of the test are shown on the following table:
207
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.
