Conservation and Innovation : Helmholtz's Struggle with Energy ...

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Volta's contact tensions in fact are not equivalent to a certain quantity of "force": they do not produce an electrical imbalance but instead originate from an electrical imbalance. For a correct interpretation of the processes it is necessary to restrict the contact law to first class conductors (metals) and realise that the second class conductors conduct only by means of an electrolytic process. Thus a contact force can be interpreted in terms of attractive and repulsive forces of the two metals which remove electrical charges of the contact area from one metal to the other. Equilibrium is reached when an electrical particle in the passage from one metal to the other does not acquire or lose living force, that is, when the variation of living force from one metal to the other is compensated by an identical variation of tension forces independently of the shape and dimension of the contact surfaces and in agreement with the galvanic series of tensions. Once more, conservation of force based on central forces gave a conceptual explicative framework. But the case was different with the long analysis of galvanic currents. Conservation of force is applied to batteries not producing polarisation, producing polarisation but not chemical decomposition and producing both. Here, as enthusiastically remarked by Helm 207, conservation is applied in the nonmechanical sense, as equivalence of numerical effects without a reinterpretation in terms of living and tension forces. The first case, batteries without polarisation, is the only one for which we have precise laws, experimentally corroborated. Through the laws of Ohm, Lenz and Joule, Helmholtz gave the amount of heat that must be generated in the circuit to have conservation of "energy". This heat has to be equivalent to the chemical heat that would be developed without electrical effects and the result is that the electromotive forces of the two metals be proportional to the difference of the heat developed through their oxidation and through their combination with acids. The case of polarisation and of polarisation with chemical decomposition is discussed in detail but only in a qualitative way, i.e. not only without the application of the conceptual scheme, but even without quantitative indications, for the lack of reliable empirical data 208. Joule is quoted again, for his experiments intended to show the equivalence of chemical and electrical heat 209. But again his results and methods are criticised 207 Helm Energetik P.44. 208 Helmholtz Erhaltung Pp.51-6 209 Joule Phil Mag XIX 1841 P.275; XX 1843 P.204; Helmholtz Erhaltung P.56.
and judged unreliable, despite providing evidence for a part, at least, of Helmholtz's innovative programme. Once more Helmholtz turned to his main line of thought: a conceptual explanation of electrical movements between metals and fluids through attractive and repulsive forces, in analogy with what he had already achieved in the case of contact forces. In the case of polarization currents the two metals would attract positive or negative electrical charges, respectively, till saturation. In the case of chemical decomposition there is not a stable equilibrium but a continuous process. The velocity of the process does not continually increase for the loss of vis viva through development of heat. An equivalence can be derived between the heat produced (living force) and the consumption of chemical elastic force (tension force). Thus Helmholtz's conservation of "energy" helped to clarify another difficult topic. Finally, Helmholtz discussed thermo-electric currents and the Peltier effect. Without applying the concepts of tension and living forces he utilized the principle of conservation to derive two consequences (on the heat produced and absorbed at equal (constant) temperatures and equal currents) but "I do not know, so far, experimental measurements for these two consequences" 210. 7 Which force equivalents for magnetism and electromagnetism? In the last chapter Helmholtz's approach reveals 211 all its fertility and limits and here the intrinsic difficulties connected with the formulation and application of the principle of conservation of "energy" can be better understood. In the section dedicated to magnetism the pattern follows the one for electrostatics: the inverse square law provides an easy expression for tension forces. Living forces and potentials are defined, both for two bodies and for a body on itself. An interesting application is the one for a non-magnetised steel bar brought close to a magnet, magnetised and separated. There is an expenditure of -1/2W in mechanical work (again the potential on itself W is twice the work ) that is acquired by the now magnetised bar 212. 210 Helmholtz Erhaltung P.60. 211 Helmholtz Erhaltung P.60-9. 212Helmholtz Erhaltung P.62-3.
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Fabio Bevilacqua Conservation and I
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different formulations 4 and priori
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and interesting results, despite th
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principle of correlation is express
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Page 11 and 12: the origin and meaning of the princ
Page 13 and 14: Whether physiological research, apa
Page 15 and 16: In a discussion on the origins of a
Page 17 and 18: his "Wärme" that one of the differ
Page 19 and 20: generate a determined equivalent of
Page 21 and 22: "Bericht", despite the application
Page 23 and 24: experiments in the most disparate b
Page 25 and 26: The premise reveals that the struct
Page 27 and 28: intelligible if it can be referred
Page 29 and 30: elevant consequence of the deductio
Page 31 and 32: Needless to say the plan was to be
Page 33 and 34: and from here that the direction an
Page 35 and 36: since Leonardo 113; the "ad nihilum
Page 37 and 38: But unfortunately for the whole str
Page 39 and 40: The principle of conservation of vi
Page 41 and 42: different from the one joining the
Page 43 and 44: "The equality that exists between e
Page 45 and 46: In virtue of its limitations to New
Page 47 and 48: Helmholtz, while asserting that lig
Page 49 and 50: the temperature of 1 Kg of water ca
Page 51 and 52: In his search for a mechanical equi
Page 53 and 54: had already been achieved in the Be
Page 55 and 56: approach is discussed at length and
Page 57 and 58: and unaware of Green's results190,
Page 59: potential function 201. It is worth
Page 63 and 64: The relevance of the first question
Page 65 and 66: principle taking this potential int
Page 67 and 68: Finally we get to the real conclusi
Page 69 and 70: conservation 234, on the theory of
Page 71 and 72: for the mechanical equivalent of he
Page 73 and 74: The controversy started with some r
Page 75 and 76: where μ are immovable masses, m th
Page 77 and 78: demonstration criticised by Clausiu
Page 79 and 80: directions that join them and whose
Page 81 and 82: quotes 288 and criticises a proposi
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Page 91 and 92: experiences in general laws of unli
Page 93 and 94: "a series of important and difficul
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Page 97 and 98: methodology. Dühring claimed the c
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efuted. But again in 1881 Helmholtz
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But was important here is that desp
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The second (1892-94), follows the i
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while the electromagnetic and the s
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can modify its specific theoric for
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considered relevant. In Poincarè
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meaning left is: "There is somethin
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interpretations at the beginning of
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while fighting metaphisicians, he w
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literature 456. There is an intrins
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assertion is surprising: it has lon
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Kant was a Naturphilosophe 480. The
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condition that work done by the for
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histories cites these (Hirn's) arti
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) the experimental determinations o
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force principle 522. Elkana tried t
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Blüh, Otto. "The Value of Inspirat
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Graetz, L. "Das Mechanische Wärme
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Helmholtz, Hermann. "Bericht über
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Helmholtz, Hermann. Wissenschaftlic
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Madison: Wisconsin U.P., 1959. Pp.
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Poincarè, Henry. Electricité et O
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Yagi, Eri."Clausius's Mathematical
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