thomson cathode ray experiment lorentz law

In adapting the pertinent hydrodynamics to the theory of the vortex atom, Thomson was guided, and perhaps even inspired, by the experiments of A. “The difficulties of this method are enormous,” Maxwell had written, “but the glory of surmounting them would be unique.” 1 Thomson’s Treatise is perhaps the most glorious episode in this hopeless struggle. In this sense the theory of the vortex atom is perhaps the most fundamental ever started, for it hoped to make do with nothing besides the several perfections of its primitive fluid and pure mathematical analysis. The theory appealed to Thomson’s romantic strain, to his recurrent wish for a quantitative, mechanistic, and “ultimate” –by which he meant not “unique” but parsimonious –account of the physical world. Here the atoms of a gas are represented as reentrant vortices in a frictionless fluid, rather like smoke rings in air but the vortices, unlike the rings, are eternal, and therefore could reproduce the permanence of the Victorian atom.

Thomson’s earliest effort at designing models was stimulated by the subject set for the Adams Prize of 1882, “a general investigation of the action upon each other of two closed vortices in a perfect incompressible fluid.” In his winning Treatise Thomson carried the matter further than required, to an application which, for him, gave it “the greater part of the interest it possesse”, namely Kelvin’s theory of the vortex atom (1867). The advantage of the first procedure is that, as Thomson would say, it fixes ideas, aids the memory, and, above all, suggests unexpected new directions of experimentation. The advantage of the second procedure, as Maxwell emphasized, is that one need not know (as one did not know) anything about the “mechanism” at work.

In the first mood, for example, Maxwell reached the equations of electromagnetism via an elaborate picture of a hydrodynamical contrivance supposed responsible for the phenomena in the second, he obtained them directly from a Lagrangian constructed from known relationships between measurable quantities. In Maxwell’s practice there is a play, and sometimes a tension, between advancing theory by developing special mechanical models or analogies and deducing basic equations from the most general dynamical relationships. He seldom abandoned an idea he had once developed.įellow of Trinity. He followed three lines of mathematical work, apparently diverse in content and style, but forming a coherent group for disciples of Maxwell and continuing research interests for himself. Thomson stayed on at Trinity, which awarded him a fellowship in 1881. He emerged second from the tripos of 1880, after Joseph Larmor, who, like himself, became a Cambridge professor. Routh, did no more than put his foot into the Cavendish Laboratory, and never met Maxwell, whose work was to inspire his own.

But one required neither knowledge nor experience of experimental physics and so Thomson, who prepared himself by following diligently the advice of his coach, E. To “wrangle” successfully, that is, to place high on the tripos list, one needed great facility at computation and an ability to cope with the sort of models, or “physical analogies,” prized by the school of Kelvin, Stokes, and Maxwell. He read for the mathematical tripos, which at that time covered a wide range of pure mathematics as well as applications to many branches of physics. He won a minor scholarship and in 1876 went up to the university where he would spend the rest of his life. On Barker’s advice Thomson remained at Owens in order to work for an entrance scholarship in mathematics offered by Barker’s old college, Trinity (Cambridge). With the help of small scholarships Thomson continued to an engineering degree at Owens College, which had an excellent scientific faculty including Osborne Reynolds, Henry Roscoe, Balfour Stewart (under whom Thomson did his first experimental work ), and Thomas Barker, the professor of mathematics, a former senior wrangler. His father, a bookseller, sent him to Owens College to mark time until a leading engineer, to whom he was to be apprenticed, had an opening but the father died before the vacancy occurred, and the family then could not afford the premium. Thomson came to physics for want of money to enter engineering. Typical values for V in television CRT’s are generally less than 50 kV so as to minimize dangerous x-rays produced when the electrons impact the phosphors on the CRT faceplate, which is often made of x-ray-absorbing leaded glass.įigure 5.1.( b.

Thomson cathode ray experiment lorentz law