Nikola Tesla - Free-Energy Devices

HIGH FREQUENCY AND HIGH POTENTIAL CURRENTS. 281consequently the inside might be considered as perfectly screened,though the potential be very rapidly alternating. Even werethe sphere filled with oil, the loss would be incomparably smallerthan when the fluid isreplaced by a gas, for in the latter case theforce produces displacements that means;impact and collisionsin the inside.No matter what the pressure of the gas may be, it becomes animportant factor in the heating of a conductor when the electricdensity is great and the frequency very high. That in the heatingof conductors by lightning discharges,air is an element ofgreat importance, is almost as certain as an experimental fact. Imay illustrate the action of the air by the following experiment:I take a short tube which is exhausted to a moderate degree andhas a platinum wire running through the middle from one endto the other.I pass a steady or low frequency current throughthe wire, and it is heated uniformly in all parts. The heatinghere is due to conduction, or frictional losses, and the gas aroundthe wire has as far as we can see no function to perform.But now let me pass sudden discharges, or high frequency currents,through the wire. Again the wire is heated, this timeprincipally on the ends and least in the middle portion ;and ifthe frequency of the impulses, or the rate of change, is highenough, the wire might as well be cut in the middle as not, forpractically all heating is due to the rarefied gas.Here the gasmight only act as a conductor of no impedance diverting the currentfrom the wire as the impedance of the latter is enormouslyincreased, and merely heating the ends of the wire by reason oftheir resistance to the passage of the discharge. But it is notat all necessary that the gas in the tube should be conducting ;might be at an extremely low stillpressure,the ends of the wirewould be heated as, however, is ascertained by experienceonly the two ends would in such case not be electrically connectedthrough the gaseous medium. Now what with these frequenciesand potentials occurs in an exhausted tube, occurs in theitlightning discharges at ordinary pressure.We only need rememberone of the facts arrived at in the course of these investigations,namely, that to impulses of very high frequency the gasat ordinary pressure behaves much in the same manner as thoughit were at moderately low pressure.I think that in lightningdischarges frequently wires or conducting objectsare volatilizedmerely because air is present, and that, were the conductor im-