Presentazione sul tema: "1796: ?Pila?. 1797: L’elettrometro condensatore, l’eliminazione dei rivelatori organici, coppie bimetalliche Rilevazione sbilancio del fluido senza la."— Transcript della presentazione:
1797: L’elettrometro condensatore, l’eliminazione dei rivelatori organici, coppie bimetalliche Rilevazione sbilancio del fluido senza la rana
200 hundred years ago: the “pile” From a region, Lombardy, once again under Austrian rule, the 20th of March 1800 a letter, written in French, is sent by an Italian scientist to the (British) Royal Society for publication in theTransactions. The author is not unknown, being a member of the Society and the recipient five years earlier of its Copley medal, but the letter is rather strange both in form and content: it claims nothing less than the discovery, today one would say the invention, of a perpetual electrical motion device, the “pile”; but rather than a proper scientific paper it is a collation of parts written in a great hurry.
In this way the fifty-five year old Alessandro Volta, for twenty-two years professor of Experimental Physics, not of natural philosophy as reported in the Transactions, at Pavia University, communicated to the world the possibility of producing stable electrical currents, a result that was to change the way of life on this planet.
Mi procuro qualche dozzina di piccole lastre rotonde o dischi di rame, di ottone, o meglio di argento, di un pollice di diametro, più o meno (ad esempio, delle monete) ed un numero eguale di lastre di stagno, o, il che è molto meglio, di zinco, e presso a poco della medesima forma e grandezza: dico presso a poco perchè non è affatto richiesta una precisione, e, in generale, la grandezza, come la forma, dei pezzi metallici è arbitraria: bisogna soltanto aver riguardo di poterli disporre comodamente gli uni sopra gli altri in forma di colonna.
Preparo inoltre un numero assai grande di dischi di cartone, di pelle, o di qualche altra materia spugnosa capace di assorbire e di ritenere molto dell'acqua o dell'umore di cui bisognerà, per il successo delle esperienze, che essi siano ben annacquati. Queste fette o dischi, che chiamerò dischi ammolliti, li faccio un po' più piccoli che i dischi o piastre metalliche, affinchè, interposti tra questi nel modo che dirò subito, essi non debordino.
Uno sguardo più accurato alla pila l’analogia con la torpedine i corpi organici come rivelatori la legge di Ohm il contatto bimetallico Qual è il modulo base della pila? La coppia bimetallica o il metallo- conduttore umido-metallo?
La pila: un ritorno ai rivelatori organici Volta ribadisce la fattorizzazione ma ha dei problemi I Francesi ribadiscono l’elettrostatica coulombiana Gli Inglesi sottolineano le reazioni chimiche Ancora oggi si dibatte
Volta: 1799 La pila Coppia bimetallica e conduttore umido
Volta’s conceptual contributions Tension, charge, capacity; electromotive force, current, resistance Factorisation of intensive and extensive factors Q=CT
Quantification and Qualification The quantification of the Baconian sciences did not follow only the non linear inverse square law of the Newtonian-Coulombian way. Linear quantification of qualities achieved through factorisation also played a relevant and lasting role For a fuller historical account the interplay between instruments and mathematics is not enough: we also need to focus on theoretical models and regulative principles
Volta’s theoretical legacy: a non standard but productive trend Alternative conceptual frameworks –Oersted, Sadi Carnot, Faraday, Mayer Factorisation –Ohm, Rankine, Ostwald, Helm, – Duhem, Sommerfeld Later on: Theoretical Physics –Helmholtz
Volta’s Theoretical Legacy Ohm explicity referred to Volta and his law is based on the product of an intensive (V) and extensive (1/R) quantity: Ohm’s law: I=V/R Carnot utilizes an approach similar to Volta’s one: the reestablishment of the equilibrium of the fluid (fire) through the tendency of an intensity factor (temperature)
Volta’s Theoretical Legacy Volta’s concept of (atmo) sphere of activity is echoed in Faraday’s electrotonic state, and the concept of vis attractiva in Faraday’s lines of force (flux tubes that attract and tend to enlarge). Lines of force, like vis attractiva, can also explain repulsion (attraction versus other bodies) Mayer in 1843 gives the first energy interpretation of the electrophorus
Volta’s Theoretical Legacy Helmholtz’s in 1847 gives the first energy interpretation of the contact of metals and of batteries. His struggle to separate the concept of Spannkraft (potential energy) from Newtonian Kraft echoes Volta’s struggle to introduce tension against force Rankine’s 1853 version of energy conservation (factorisation) is based on the product of an intensity factor by an extensive one
Volta’s Theoretical Legacy Factorisation was a main part of the energetics in the works of Ostwald, Helm and Duhem Sommerfeld still proposed this distinction in electromagnetism in the 1940’s, in his “advanced” textbook. And so we can close the hermeneutical Voltaic circle!!!
Volta’s Primary Sources Archives Papers and Letters Instruments
Volta’s Sources: Archives Istituto Lombardo di Scienze e Lettere
Volta’s Historiography A bit of history of historiography is necessary Massardi and Polvani Heilbron Pera e Bernardi Pancaldi e Fregonese
The Received View Classical sciences (general physics, quadrivium) challenged by Baconian Sciences (particular, experimental physics) undergoing a process of quantification and mathematization along Newtonian- Coulombian lines Enlightenment and quantification “Standard Model” of particles and fluids and interactions
The Nuova Voltiana Restaging Volta’s Natural Philosophy There is a need for: a better understanding of Volta’s work in close connection with the path followed by the physical sciences from “natural philosophy” to the form and contents they assumed by the end of the eighteenth century. a more effective understanding of both his conceptual world and the extent to which it was embodied in the numerous instruments he invented.
Nuova Voltiana Journal of Voltaic Studies First Issues: papers presented at the WORKSHOP: Alessandro Volta between Natural Philosophy, Chemistry and Physics December 1999 Abbri: Volta’s chemical theories: The first two phases Agazzi: The impact of Alessandro Volta on German culture Bensaude: A glimpse on pneumatic chemistry from Pavia
Nuova Voltiana Beretta: Volta and aerial medicine: Salubrity and respirability of air at the end of the 18th century Bernardi: The controversy on animal electricity in eighteenth-century Italy: Galvani, Volta and other protagonists Brambilla: Scientific and professional education in Lombardy, 1760-1803: Physics between medicine and engineering Brenni-Bellodi: “The arms of the physicist” Volta and scientific instruments
Nuova Voltiana Ciardi: Falling stars, instruments and myths. Alessandro Volta and the birth of modern meteorology Gigli Berzolari: Volta's teaching in Como and Pavia: Moments of academic life under all flags Hackmann: The enigma of Volta’s ‘contact tension’ and the development of the ‘dry pile’ Heilbron: Analogy in Volta's exact natural philosophy Holmes: Phlogiston in the air
Nuova Voltiana Home: Volta’s English connections Hutchison: Forces and facts: Yet another fragment of the explanation for late 18C dynamism Kipnis: Debating the nature of the voltaic electricity, 1800-1850 Kleinert: Volta and the German controversy about physics and Naturphilosophie, and Volta's relations with Johann Wilhelm Ritter Kragh: Confusion and Controversy: Nineteenth- Century Theories of the Voltaic Pile
Nuova Voltiana Martins: Romagnosi and Volta’s pile: Early difficulties in the interpretation of voltaic electricity Pepe: Volta, the "Istituto Nazionale" and scientific communication in early 19th-century Italy Seligardi: Volta and the synthesis of water: Some reasons for a missed discovery Teichmann: Volta and the quantitative conceptualisation of electricity: From electrical capacity to the preconception of Ohm’s law
Volta and the Web www.Cilea.it/Volta99 Click “Alessandro Volta” and see: A biography The Cabinet The Collected Works A bibliography