Nikola Tesla: Colorado Springs Notes, 1899-1900 Page 407

from the resonant frequency of the secondary circuit and the known primary inductance (one turn) he finds the required capacity of the primary circuit. He then checks whether this capacity can be used with an LF transformer of the given power. The formula is approximate, but gives a good rough guide for the power in the mains transformer. The peak power rating of the transformer must be even greater than the value found because the condenser is not charging all the time but only in short pulses.

July 5

It is possible that Tesla was planning to construct a balloon to take an antenna to great height^{(13, 14)}, and was therefore interested in the generation of hydrogen. He does not give any indication, however, of whether he actually carried out any experiments in this direction, or of the grounds he had for expecting the desired decomposition to take place.

July 7

For the "resonance method" Tesla envisaged two possible types of resonant transformer: one with loose coupling between the primary and secondary, and the other with tight coupling but only with part of the secondary inductance^*. This latter type he protected under the patent "Apparatus for transmitting electrical energy", for which he applied on 18 January 1902⁽⁴⁴⁾; a good deal of his time at Colorado Springs was spent in developing it.

His conclusions about various parameters of the oscillator indicate that he had by then gained sufficient experience to be able to design such devices with improved performance in the parameters he wanted. As the experiments proceeded he gradually increased the voltage of the LF power supply. On June 20th he had calculated with an excitation voltage of 20 kV, but he had assumed a much higher rate of charging of the condenser, so that he obtained then a greater power than now with 40kV. The difference in the number of chargings per second is nowhere explained, nor had he ever previously described how it was calculated. The first time he had probably taken it as being equal to the number of breaks on the rotary discharger, and the second time as double the mains frequency. In this light the accuracy of "the capacity of condenser which the transformer will be able to charge" is dubious. However, Tesla did not take the value he calculated as limiting the capacitance in the primary, noting that it did not take into account resonance and other factors which might enable the transformer to charge a much larger condenser.

July 8

From observing the behaviour of his oscillator Tesla came to an interesting conclusion concerning the shape of the conductor of the primary winding, i.e. that a strip conductor was better than a wire of circular cross section because all other conditions being the same it did not get so hot. He believed that there was a special reason for this "not yet satisfactorily explained". Since the dimensions of the strip conductor are not known we cannot work out the reduction in resistance relative to a circular section conductor due to the