In 1887, Heinrich Hertz announced that he had discovered electromagnetic waves, an achievement at that time of no small import.
In 1889, Nikola Tesla attempted the reproduction of these Hertzian experiments. Conducted with absolute exactness in his elegant South Fifth Avenue Laboratory, Tesla found himself incapable of producing the reported effects. No means however applied would produce the effects which Hertz claimed.
Tesla began experimenting with abrupt and powerful electric discharges, using capacitors charged to very high potentials. He found it possible to explode thin wires with these abrupt discharges. Dimly perceiving something of importance in this experimental series, Tesla abandoned these experiments, all the while pondering the mystery and suspecting that Hertz had somehow mistakenly associated electrostatic inductions or electrified shockwaves in air for true electromagnetic waves. In fact, Tesla visited Hertz and personally proved these refined observations to Hertz who, being convinced that Tesla was correct, was about to withdraw his thesis. Hertz was truly disappointed, and Tesla greatly regretted having to go to such lengths with an esteemed academician in order to prove a point.
But while endeavoring toward his own means for identifying electrical waves, Tesla was blessed with an accidental observation, which forever changed the course of his experimental investigations. In his own attempts to achieve where he felt Hertz had failed, Tesla developed a powerful method by which he hoped to generate and detect real electromagnetic waves. Part of this apparatus required the implementation of a very powerful capacitor bank. This capacitor “battery” was charged to very high voltages, and subsequently discharged through short copper bus bars. The explosive bursts thus obtained produced several phenomena, which deeply impressed Tesla, far exceeding the power of any electrical display he had ever seen. These proved to hold an essential secret, which he was determined to uncover.
The abrupt sparks, which he termed “disruptive discharges”, were found capable of exploding wires into vapor. They propelled very sharp shockwaves, which struck him with great force across the whole front of his body. Of this surprising physical effect, Tesla was exceedingly intrigued. Rather, more like gunshots of extraordinary power than electrical sparks, Tesla was completely absorbed in this new study. These electrical impulses produced effects commonly associated only with lightning. The explosive effects reminded him of similar occurrences observed with high voltage DC generators. A familiar experience among workers and engineers, the simple closing of a switch on a high voltage dynamo often brought a stinging shock, the assumed result of residual static charging.
This hazardous condition only occurred with the sudden application of high voltage DC. This crown of deadly static charge stood straight out of highly electrified conductors, often seeking ground paths which included workmen and switchboard operators. In long cables, this instantaneous charge effect produced a hedge of bluish needles, pointing straight away from the line into the surrounding space. The hazardous condition appeared briefly at the very instant of switch closure. The bluish sparking crown vanished a few milliseconds later, along with the life of any unfortunate who happened to have been so “struck”. After the brief effect passed, systems behaved as designed. Such phenomena vanished as charges slowly saturated the lines and systems. After this brief surge, currents flowed smoothly and evenly as designed.
The effect was a nuisance in small systems. But in large regional power systems where voltages were excessive, it proved deadly. Men were killed by the effect, which spread its deadly electrostatic crown of sparks throughout component systems. Though generators were rated at a few thousand volts, such mysterious surges represented hundreds of thousands, even millions of volts. The problem was eliminated through the use of highly insulated, heavily grounded relay switches. Former engineering studies considered only those features of power systems that accommodated the steady state supply and consumption of power. It seemed as though large systems required both surge and normal operative design considerations. Accommodating the dangerous initial “supercharge” was a new feature. This engineering study became the prime focus of power companies for years afterward, safety devices and surge protectors being the subject of a great many patents and texts.
Tesla knew that the strange supercharging effect was only observed at the very instant in which dynamos were applied to wire lines, just as in his explosive capacitor discharges. Though the two instances were completely different, they both produced the very same effects. The instantaneous surge supplied by dynamos briefly appeared superconcentrated in long lines. Tesla calculated that this electrostatic concentration was several orders in magnitude greater than any voltage that the dynamo could supply. The actual supply was somehow being amplified or transformed.
But how?
The general consensus among engineers was that this was an electrostatic “chocking” effect. Many concluded it to be a “bunching” action, where powerfully applied force was unable to move charge quickly through a system. Mysterious, the combined resistance of such systems seemed to influence the charge carriers before they were able to move away from the dynamo terminals! Like slapping water with a rapid hand, the surface seemed solid. So also it was with the electrical force, charges meeting up against a seemingly solid wall. But the effect lasted only as long as the impact. Until current carriers had actually “caught up” with the applied electrical field, the charges sprang from the line in all directions. A brief supercharging effect could be expected until the charges were distributed, smoothly flowing through the whole line and system. The dynamo itself thus became the brief scene of a minor shockwave.
He began wondering why it was possible for electrostatic fields to move more quickly than the actual charges themselves, a perplexing mystery. Was the field itself an entity that simply drive the more massive charges along? If this was true, then of what was the electrostatic field itself “composed”? Was it a field of smaller particles? The questions were wonderfully endless. Despite the wonderful ideas, which this study stimulated, Tesla saw a practical application that had never occurred to him. Consideration of the dynamo supercharging effect suggested a new experimental apparatus. It was one that could greatly outperform his capacitor battery in the search to find electrical waves.
A simple high voltage DC generator provided his electric field source. Tesla understood that the resistance of lines or components, viewed from the dynamo end, seemed to be an impossible “barrier” for charge carriers to penetrate. This barrier caused the “bunching” effect. Electrostatic charges were literally stopped and held for an instant by line resistance, a barrier which only existed during the brief millisecond interval in which the power switch was closed. The sudden force application against this virtual barrier squeezed charge into a density impossible to obtain with ordinary capacitors. It was the brief application of power, the impact of the charge against the resistance barrier, which brought this abnormal electro-densified condition. This is why the conductive wires in his present experiment often exploded.
The academic world of experimenters was yet fixated on his former discovery of high frequency alternating currents. It seemed that Tesla alone now exclusively studied these impulse discharges. He was producing explosive impulses, which had not been observed in laboratories. Every component was carefully insulated, himself implementing insulator rods and rubberized regalia to insure complete safety. Tesla had observed electrostatic machines whose ability to charge insulated metals was potent, but this demonstration exceeded the mere charging of wire by the instantaneous switch closure. This effect produced “springing” charge, phenomena like no other before witnessed by Tesla for its sheer strength. Whatever the conditions observed in previous systems, he had now learned how to maximize the effect. Balancing voltage and resistance against capacity, Tesla learned to routinely produce supercharge states which no existing device could equal.
Empirical observation had long taught that ordinary capacitor discharges were oscillating currents, spark currents which literally “bounced” between each capacitor plate until their stored energy was wasted away. The high voltage of the dynamo exerted such an intense unidirectional pressure on the densified charges that alternations were impossible. The only possible backrushes were oscillations. In this case, charges surged and stopped in a long series until the supercharge was wasted away. All parameters which forced such oscillations actually limited the supercharge from manifesting its total energetic supply, a condition Tesla strove to eliminate. Indeed he spent an excessive time developing various means to block every “backrush” and other complex current echo which might force the supercharge to prematurely waste its dense energy. Here was an effect demanding a single unidirectional super pulse. With both the oscillations and alternations eliminated, new and strange effects began making their appearance. These powerful and penetrating phenomena were never observed when working with high frequency alternations.
The sudden quick closure of the switch now brought a penetrating shockwave throughout the laboratory, one that could be felt both as a sharp pressure and a penetrating electrical irritation. A “sting”. Face and hands were especially sensitive to the explosive shockwaves, which also produced a curious “stinging” effect at close range. Tesla believed that material particles approaching the vapor state were literally thrust out of the wires in all directions. In order to better study these effects, he poised himself behind a glass shield and resumed the study. Despite the shield, both shockwaves and stinging effects were felt by the now mystified Tesla. This anomaly provoked a curiosity of the very deepest kind, for such a thing was never before observed. More powerful and penetrating than the mere electrostatic charging of metals, this phenomenon literally propelled high voltage charge out into the surrounding space where it was felt as a stinging sensation. The stings lasting for a small fraction of a second, the instant of switch closure. But Tesla believed that these strange effects were a simple effect of ionized shockwaves in the air, rather like a strongly ionized thunderclap.
Tesla devised a new series of experiments to measure the shockwave pressure from a greater distance. He required an automatic “trip switch”. With this properly arranged, a more controlled and repetitious triggering of the effect was possible. In addition, this arrangement permitted distant observations which might cast more light on the shieldpermeating phenomenon. Controlling the speed of the high voltage dynamo controlled the voltage. With these components properly adjusted, Tesla was able to walk around his large gallery spaces and make observations. Wishing also to avoid the continuous pressure barrage and its stinging sparks, Tesla shielded himself with several materials. The arrangement of rapidly interrupted high voltage direct currents resulted in the radiation of stinging rays, which could be felt at great distances from their super-sparking source. In fact, Tesla felt the stings right through the shields! Whatever had been released from the wires during the instant of switch closure, successfully penetrated the shields of glass and of copper. It made no difference; the effect permeated each substance as if the shield were not there at all. Here was an electrical effect that communicated directly through space without material connections. Radiant electricity!
In these several new observations, the phenomenon was violating electrostatic charge principles experimentally established by Faraday. Projected electrostatic charges normally spread out over the surface of a metallic shield; they do no penetrate metal. This effect had certain very non-electrical characteristics. Tesla was truly mystified by this strange new phenomenon, and searched the literature for references to its characteristics. No such reference was found, except in the surreptitious observations of two experimenters. In one case, Joseph Henry observed the magnetization of steel needles by a heavy spark discharge. The extraordinary feature of this observation (1842) lay in the fact that the Leyden jar, whose spark apparently produced the magnetizations, stood on the upper floor of an otherwise electrically impervious building. Brick walls, thick oak doors, heavy stone and iron flooring, tin ceilings. Moreover, the steel needles were housed in a vault in the cellar. How did the spark affect such a change through such a natural barrier? Dr. Henry believed that the spark had released special “light-like rays”, and these were the penetrating agencies responsible for the magnetizations.
A second such account (1872) occurred in a high school building in Philadelphia. Elihu Thomson, a physics instructor, sought to make the sparks of a large Ruhmkorrf Spark Coil more visible for his next lecture. Attaching one pole of the coil to a cold water pipe, and reactivating the coil, Thomson was thrilled to find that the nature of the spark had changed from blue to white. Wishing to amplify this effect, Thomson attached the other pole to a large metal tabletop. Again reactivating the coil produced a shrieking silver-white spark, entirely visible to any whom sat in the last row. Wishing to show this to a colleague, Edwin Houston, Thomson made for the door and was abruptly stopped. Touching the brass knob on the otherwise insulated oak door, Thomson received an unexpected sizzling shock. Turning off the Ruhmkorrf Coil, Thomson found it possible to stop the effect. Calling for Edwin, he summarized what had occurred. Then turning the unit back on again, the stinging charge effects returned. The two gentlemen ran throughout the huge stone, oak, and iron building with insulated metal objects now. Each touch of a penknife or screwdriver to anything metallic, however distant from the coil or insulted from the floor, produced long and continuous white sparks. The account was written up as a short article in Scientific American later in the same year.
https://imrich.world/2019/06/08/wide-range-of-phenomena-created-by-disruptive-discharges/
