Nikola Tesla U.S. Patent 512,340 - Coil for Electro-Magnets Patent Wrapper Page 4

4 Oven 2 helices, solenoids, or, in fact, any conductor the different parts of which by the requirements of its application or use are brought in to such relations with each other as to materially increase the self-induction. (4) hat in every coil there exists a certain relation between its self-induction and capacity that permits a current of given frequency and potential to pass through it with no other opposition than that of ohmic resistance, or, in other words, as though it possessed no self-induction. This is due to the mutual relations existing between the special character of the current and the self-induction and capacity of the coil, the latter quantity being just capable of neutra lizing the self-induction for that frequency. It is well-known that the higher the frequency or potential difference of the current the smaller the have fou capacity required to counteract the self-induction, hence, in any coil, however small the capacity, it may be sufficient for the purpose stated if the proper conditions in other respects be secured. In the ordinary coils the difference of potential between adjacent turns or spires is very small, so that while they are in a sense condensers, they possess but very small capacity and the relations between the two quantities, self-induction and capacity, are not such as under any ordinary conditions satisfy the requirements herein contemplated, because the capacity -2