ELECTRICITY

Evening Star, Issue 19789, 13 February 1928, Page 1

ELECTRICITY

RECENT RESEARCH SIR E. RUTHERFORD'S SURVEY Sir Ernest Rutherford, 0.M., in the course of the anniversary address which he delivered at Burlington House, Piccadilly, as president of the Fellows of the Royal Society, announced the return of Die society to its old tradition of having experiments shown week by week in connection with the ordinary weekly meetings, states the ‘ Manchester Guardian.’ The greater part of his address, however, was devoted to the results of investigations carried out in recent years to produce intense magnetic fields and high voltages for general scientific purposes. After deploring tho sparse attendances at certain of the ordinary meetings, he said that in the early days of the society it was customary for members and their friends to perform experiments of special interest before the fellows, quite apart from any question of publication, and they knew from the history of Dio society the importance attached to such demonstrations and their value in disseminating information in various branches of science. The custom gradually fell into abeyance, probably as a result of everincreasing specialisation. It had occurred to some of the members that it would be a definite advantage to the society if the old custom were revived, and the members encouraged to show experiments of special interest and novelty before the beginning of tho ordinary meeting. In order to give tho suggestion a fair trial portable demonstration tables had been placed in the tea room, with connections for water, gas, and electric current. He trusted that the fellows would not only avail themselves of Diese facilities but also encourage their scientific friends to do EO.

LIGHTNING FLASHES IN MINIATURE.

Turning to Die production of intense magnetic fields and high voltages for general scientific purposes, Sir Ernest Rutherford said that in the past Dm laboratories had had to he content with the comparatively weak magnetic fields provided by Die ordinary electric magnets and tho voltages supplied by simple electro static machines and induction coils, but in order to push further investigations in many directions much stronger magnetic fields and higher voltages were required in the laboratory. The most general method of obtaining high voltages was by the use of a cascade of transformers, each successive transformer multiplying the voltage of the one preceding it. Such a high-tension plant in full operation was a striking sight, giving a torrent of sparks several yards in length and resembling a rapid succession of lightning Hashes on the small scale. But actually the highest voltage so far obtained by these methods was incomparable with the voltage of a normal lightning Hash, which might be as high as 1,000 million volts. There seemed no obvious limit to the voltages obtainable by the cascade arrangement of transformers except that of expense and space occupied. He understood that tho General Electric - Company of Schenectady had a plant giving 2,800,000 volts, and Diat a (3,000,000-volt plant was being constructed. Recently Dr (Joolidgo had constructed an electron tube which would stand 300,000 volts, the rays passing into the air through a thin plate of chrome-nickcl-iron alloy about 0.0005 inch thick. Experiments made up to Die present with three such tubes in series and a voltage of 900,000 had been made so successfully (hat a beam of high-velocity electrons had been projected into Dio air for a distance of over oft from the thin plate or window. Further experiments with even higher voltages were being planned at the' moment. But so far the success of the radio-active elements had not even been approached. A voltage of more than two million would be required to produce X-rays of the penetrating power of the gamma rays, and still more for the swiftest beta rays from radium, while alpha particles were liberated from radium C with an energy of 7.6 million electron volts.

Ib had long been bis ambition to have available for study a copious supply of atoms ami electrons which had an individual energy far transcending that of the alpha and beta, particles from radio-active bodies. Ho was hopeful that he might yet have his wish fulfilled, but it was obvious that many experimental difficulties would have to be surmounted before this could he realised, even on a laboratory scale. INTENSE MAGNETIC FIELDS. Emphasising the necessity for intense magnetic fields in order to pursue these researches, Sir Ernest said that Professor Cotton, of Paris, had under construction a very large electro-magnet which would have an area of a square metre and would be energised by 500 kilowatts. He did not doubt that this electro-magnet would prove very useful in experiments where steady fields of high i.density were required through a reasonable volume. To provide magnetic fields of the order of half a million gauss, the oicctro-magiict must be abandoned. Some years ago, Dr Kapitza had suggested that intense momentary magnetic fields could be obtained by sending a very strong current through a- coil for such a short time that the heating of the coil could be neglected, and it had been possible to construct a coil giving a iield of 320,000 gauss over a volume of about 3 c.0.m., and measurements bad been regularly made in such a field in the hundredth of a second available. It was anticipated that the present design of coil would give about 500,000 gauss before bursting, “The application of these now methods of producing intense fields,” he concluded, “ opened up a wide region of research where all magnetic properties could be examined in fields ten to twenty times stronger than those hitherto available. Such reI searches could not fail to yield results I of great interest and importance, and to advance knowledge of magnetic phenomena. While the application of external magnetic fields of the order of one million gauss will no doubt markedly perturb (he orbits of electrons in the outer structure of the atom, it is not (o be anticipated that it will seriously affect the stability of atomic nuclei. General evidence indicates- that the magnetic fields within the are much too great for such a relatively weak external field to canre a disruption of the nucleus. In this direction the bombardment by high-speed particles is likely to be far more effective than the strongest magnetic field we can hope to generate. “The advance of science depends to a large extent on the development of new technical methods and their application to scientific problems. The recent work to which 1 have referred on the development of methods of producing high voltages and intense magnetic fields is not only of great interest to scientjlic men in itself, but promises to provide us with more powerful methods of attack on a number of fundamental problems.” '