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A questão da conservação da energia é analisada juntamente com as conclusões obtidas na remontagem de uma experiência de Berthollet de 1809, caracterizada pelo aumento da temperatura dos discos metálicos após terem sofrido o esmagamento por compressão. São analisadas duas formas de energia: calor e trabalho e o seu estudo é limitado ao período que vai desde os fins do século XVIII até à primeira metade do século XIX. A primeira parte da Tese é dedicada aos conceitos da energia e da conservação de energia. É explicado o interesse que o fenómeno da combustão suscitou a partir do século XVIII na sua relação com o desenvolvimento do conceito do calor. Neste período, a presença da máquina a vapor propiciou a Sadi Carnot a possibilidade de calcular a potência da sua força motriz. É mostrado nesta Tese como uma modificação na forma deste cálculo permitiria encontrar o equivalente mecânico do calor. É apresentada a história da teoria do calórico em confronto com a interpretação dinâmica da natureza do calor. Descrevem-se os trabalhos de Mayer e Joule para a determinação do equivalente mecânico do calor, num período em que se consolidava o princípio da conservação de energia. Esta primeira parte termina com a interrogação: o que é a energia? Na parte experimental da Tese descreve-se o método seguido para a remontagem da experiência que inclui a análise do contexto cultural da época de Berthollet. Neste sentido, são analisadas as experiências de Pictet, Tilloch, Dalton e Haldat. Os ensaios da experiência a remontar foram previamente preparados em laboratório antes da sua instalação em ambiente fabril similar ao escolhido em 1809 por Berthollet. De acordo com a programação dos ensaios, após terem sofrido sucessivos choques inelásticos, os aumentos da temperatura observados para os discos metálicos são da ordem de grandeza dos resultados registados por Berthollet. Porque, na sua época, não lhe era possível ter as condições e equipamento agora disponível, a experiência remontada permitiu a determinação do equivalente mecânico do calor. Por fim, apresenta-se uma análise aos resultados relatados por Berthollet.
The issue of conservation of energy is analyzed together with the conclusions obtained in the reconstruction of an experiment made by Berthollet in 1809, characterized by the increase in the temperature of metal disks after they have been crushed by compression. Two forms of energy are analyzed: heat and work, and their study is limited to the period from the end of the 18th century to the first half of the 19th century. The first part of the Thesis is dedicated to the analysis of the concepts of energy and energy conservation. The interest that the phenomenon of combustion aroused from the 18th century onwards, in its relationship with the development of the concept of heat is explained. During this period, the appearance of the steam engine motivated Sadi Carnot to determine the power of its driving force. This Thesis shows how a modification in this calculation would allow the mechanical equivalent of heat to be calculated. The history of caloric theory is presented in comparison with the dynamic interpretation of the nature of heat. The works of Mayer and Joule for the determination of the mechanical equivalent of heat are presented when the principle of conservation of energy was being consolidated. This first part concludes with the question: what is energy? In the experimental part of the Thesis, the method followed for the reconstruction of the experiment is described, which includes an analysis of the cultural context of Berthollet's environment. In this regard, the experiments of Pictet, Tilloch, Dalton and Haldat are studied. The tests of the experiment to be reconstructed were previously prepared in the laboratory before being installed in a factory like that chosen in 1809 by Berthollet. According to the test schedule, after having suffered successive inelastic shocks, the temperature increases of the metal discs are on the order of magnitude of the results recorded by Berthollet. Because, in his time, he did not have the conditions and equipment now available, the reconstructed experiment allowed the determination of the mechanical equivalent of heat. Finally, an analysis of the results reported by Berthollet is presented.
The issue of conservation of energy is analyzed together with the conclusions obtained in the reconstruction of an experiment made by Berthollet in 1809, characterized by the increase in the temperature of metal disks after they have been crushed by compression. Two forms of energy are analyzed: heat and work, and their study is limited to the period from the end of the 18th century to the first half of the 19th century. The first part of the Thesis is dedicated to the analysis of the concepts of energy and energy conservation. The interest that the phenomenon of combustion aroused from the 18th century onwards, in its relationship with the development of the concept of heat is explained. During this period, the appearance of the steam engine motivated Sadi Carnot to determine the power of its driving force. This Thesis shows how a modification in this calculation would allow the mechanical equivalent of heat to be calculated. The history of caloric theory is presented in comparison with the dynamic interpretation of the nature of heat. The works of Mayer and Joule for the determination of the mechanical equivalent of heat are presented when the principle of conservation of energy was being consolidated. This first part concludes with the question: what is energy? In the experimental part of the Thesis, the method followed for the reconstruction of the experiment is described, which includes an analysis of the cultural context of Berthollet's environment. In this regard, the experiments of Pictet, Tilloch, Dalton and Haldat are studied. The tests of the experiment to be reconstructed were previously prepared in the laboratory before being installed in a factory like that chosen in 1809 by Berthollet. According to the test schedule, after having suffered successive inelastic shocks, the temperature increases of the metal discs are on the order of magnitude of the results recorded by Berthollet. Because, in his time, he did not have the conditions and equipment now available, the reconstructed experiment allowed the determination of the mechanical equivalent of heat. Finally, an analysis of the results reported by Berthollet is presented.
Descrição
Tese de doutoramento em História e Filosofia das Ciências, Universidade de Lisboa, Faculdade de Ciências, 2026.
Palavras-chave
energy energy conservation experiment reconstruction mechanical equivalent of heat C. L. Berthollet energia conservação de energia remontagem de experiência equivalente mecânico do calor C. L. Berthollet