Nikola Tesla Books
Books written by or about Nikola Tesla
New condensers proposed: old ones being inadequate to stand the strain beyond 15,000 volts on two dielectrics, it would be necessary to resort to four sets when using higher pressure and this would make condenser boxes too bulky. It is now proposed to use new bottles of lead glass (Bethesda Mineral Water). These are, as nearly as can be ascertained, twice or rather more than twice thicker than the old bottles. The comparison of capacities was made today for this purpose. The new bottles were filled up to 10" from the bottom and immersed in a tin tank. The old bottles were filled up to 9" from the bottom and immersed in a tank. A solution was prepared from rock salt as concentrated as practicable and care was taken that the liquid was at equal height outside and inside. The readings were:
| New bottle: | Old bottle: | |||||||
| Volt | Defl. | Average: | Volt | Defl. | Average: | |||
| 180 | 6.5 | Defl. 6.5 |
Volt 181 |
180 | 9 trifle less | Defl. 9 |
Volt 182 |
|
| 181 | 6.5+trifle | 182 | 9 much less | |||||
| 179 | 6.5 | 180 | 9 trifle less | |||||
$!{{Weight \, of \, old \, bottle} \over {Weight \, of \, new \, bottle}}$! measured $!{17 \over 21}$!.
From this result the thickness of the walls was first estimated. This not affording a sure test, some bottles were broken and the average showed that new bottles were twice as thick as old ones.
$!{\mathrm{Capacity\,of\,new\,bottle} \over \mathrm{Capacity\,of\,old\,bottle}}$! from measurement before made was as $!65\over90$!.
Taking for comparison specific inductive capacity of old bottle glass 1, we have 65:90=0.722. Now, for the same glass, the capacity of a new jar would have been 0.722x2=1.444 times that of old, hence the new glass has 44.4% higher specific inductive capacity. It is still not certain, in view of unequal size, whether 25 or 20 or possibly only 18 will go in tank. Taking 18 to be the lowest figure for new bottles in one tank then $!{New \, tank \over Old \, tank}$! will be as $!{{65 \over 90} \times {18 \over 16}}$! or about $!8\over10$!. For 20 bottles in the new tank this ratio will be nearly $!9\over10$!, for 25 jars nearly 1.11. In the least favorable case, the first, we shall be able to transform at least 60% more energy than with the old jars; in the best case 2.22 times as much as before. This is good.
112
July 29
To check out his theoretical conclusions about the free oscillation of the “extra coil” (see 30 June and 26 July) Tesla made a new coil with a higher inductance. As this was his first experiment with the new coil, he had to adjust the circuit parameters by trial and error.
Tesla's ingenuity found full expression in the way in which he developed condensers for high voltages. He filed a patent application on his design for a fluid electrolyte condenser on June 17th 1896(67).
July 29
For the purpose of theoretical conclusions of "additional coil", free vibrations checking (please see June 30 and July 26) Tesla constructs a new coil with higher inductance than previously. With this new ''additional coil'' he puts the oscillator in operation. As he used to do it, he weighs the inductance in primary circuit (means of regulating coil) and numcer of jars (i.e. capacitance) so as to obtain the maximum voltage in the secondary. The rough estimate of operating frequency obtained on the basis of inductance and capacitance in the primary.
When adjusting arcing device (please see July 27) he observes that the bulb on the network supply feeder gives a brighter light when there is no spark on the arcing device. He is not sure whether the reason is capacitive loading of the Westinghouse transformer (network transformer) which could cause a resonant overvoltage. He suspects "electrostatic action" and gives his opinion on that phenomenon.
During the process of looking for the conditions for best oscillator operations, Tesla checks the circuit parameters. He matches the primary capacitance according to supply transformer power. By capacitance increase in the primary he provides a larger energy transfer, but the best results are obtained when the system operates at suitable frequency. The operating system he applies here could be named "test and guessing method", which is understandable with regards to his first experiments with new "additional coil".
"Additional coil" described on June 29 was wourid on the same core as the coil which he uses now, but with approximately twice as many turns. Tesla expected that the new coil's self-resonant frequency will be approximately twn times lower. That is why, when testing the oscillator, he reduced its frequency by increasing the primary capacitance. When that didn't provide the expected results, he reduced the inductance (by connecting two primary turns in parallel instead of in series) and when he obtained good sparks, he stopped at that. From the description of the sparks some kind of enthusiasm is evident, and the writing method is such that one almost forgets that the description of a physical event is in question.
By gradually increasing the exciting network transformer voltage (he came to 22,500 V), Tesla achieved the capacitor withstand limit. The capacitor was made of glass jars. In order to avoid the numerous jars connected in series for the purpose of high voltage achievement, he tests another kind of jar with thicker walls.
When one has in mind the complexity of technical venture of capacitor production for such high voltages, the simplicity with which Tesla solved that problem is very impressive. Capacitor design with fluid electrodes, Tesla protected by patents submitted on June 17, 1897(67).
* Possible by mistake, Tesla designated both sensitive devices with A'. In text A and A' appear, and on the given drawing the correction has been made. In the original text, Tesla, talking about device sensitivity, mentioned the experiments with sensitive device A' which required the text correction with regard to the above correction.
