Nikola Tesla - Free-Energy Devices

172 INVENTION'S OF NIKOLA TE8LA.shown, may be as much as sixteen times greaterthan that at ordinarytemperatures. If the iron core were perfectly enclosed,it would not be deteriorated by the heat, and, if the enclosure oftire-proof material would be sufficiently thick, only a limitedamount of energy could be radiated in spite of the high temperature.Transformers have been constructed by me on thatplan, but for lack of time, no thorough tests have as yet beenmade.Another way of adapting the iron core to rapid alternations,or, generally speaking, reducing the frictional losses, is to produceby continuous magnetization a flow of something like seventhousand or eight thousand lines per square centimetre throughthe core, and then work with weak magnetizing forces and preferablyhigh frequencies around the point of greatest permeability.A higher efficiency of conversion and greater output areobtainable in this manner. I have also employed this principlein connection with machines in which there is no reversal ofpolarity. In these types of machines, as long as there are onlyfew pole projections, there is no great gain, as the maxima andminima of magnetization are far from the point of maximumpermeability ; but when the number of the pole projectionsisvery great, the required rate of change may be obtained, withoutthe magnetization varying so far as to depart greatly from thepoint of maximum permeability, and the is gain considerable.The above described arrangements refer only to the use ofcommercial coils as ordinarily constructed. If it is desired toconstruct a coil for the express purpose of performing with itsuch experiments as I have described, or, generally, renderingitcapable of withstanding the greatest possible difference of potential,then a construction as indicated in Fig. 113 will be found ofadvantage. The coil in this case is formed of two independentparts which are wound oppositely, the connection between bothbeing made near the primary. The potential in the middle beingzero, there is not much tendency tojump to the primary and notmuch insulation is required. In some cases the middle pointmay, however, be connected to the primary or to the ground. Insuch a coil the places of greatest difference of potential are farapart and the coil is capable of withstanding an enormous strain.The two parts may be movable so as to allow a slight adjustmentof the capacity effect.As to the manner of insulating the coil, it will be found con-