Abstract
IN the Electrician of September 21, an account is given of experiments carried out in the high-voltage laboratory of the International General Electric Co. at Pittsfield, Mass., where artificial lightning at ten million volts was first produced. The engineers of the company have observed the effects pro duced by electric currents up to a quarter of a million amperes, which is much greater than any currents hitherto obtained. The object of the research was to find out the best way of protecting electric equipment against lightning discharges. A copper wire one tenth of an inch in diameter was completely vapourised in the few millionths of a second required for the discharge. When a piece of iron wire was used, it ‘exploded’, the ends of the wire that were left remaining white hot for several seconds A section of reinforced concrete placed between the electrodes was broken into bits by the current in the same way that a concrete structure is shattered when struck by natural lightning. Most of a silver-plated tea-spoon vanished in a shower of sparks, but the bowl, discoloured by heat, was left. Metallic armoured cable was in some cases destroyed, and occasionally caught fire. If the arc is confined to a small fibre tube, the tremendous pressure de veloped blows the tube to pieces even although it has a wall a quarter of an inch thick. In the open air, the pressure produced by the discharge shatters a pane of glass several inches away. When the current is passed through a flat copper strip, the strip is crumpled until its section is nearly round. The high ampere generator is formed by a battery of condensers suitably arranged. The discharges have to be confined within strong protecting cylinders as the explosion is very violent and makes a loud report.
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Effects Produced by Large Electric Currents. Nature 134, 490 (1934). https://doi.org/10.1038/134490c0
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DOI: https://doi.org/10.1038/134490c0