A history of Ohm's Law: Investigating the flow of electrical ideas through the instruments of their production

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Connelly, Charlotte  ORCID logo  https://orcid.org/0000-0001-9350-044X

This thesis takes a deep dive into the electrical work of Georg Simon Ohm. It is tightly focused on the period 1825-1827 when he developed and published the famous law we now think of as “Ohm’s law”. This work differs from previous studies of Ohm’s investigations by putting material culture at its heart. Using Ohm’s research as a case study, this project asks: how can the material culture of the physical sciences contribute to contemporary historiography in the history of science? What can we uncover from a material-led investigation that would remain inaccessible in a text-led investigation? And, in this particular case, how does looking closely at Ohm’s experimental apparatus and practice help us to understand the development of his law? As part of the material-led study, this project incorporates a reconstruction and reworking of Ohm’s 1826 experimental apparatus. As something of an outsider, Ohm has defied ready categorisation by historians. This project looks at why that might be, and what his theoretical and methodological influences were. Looking at the way Ohm’s instrument was designed and used, we can see the influence of natural philosophers including Coulomb, Ørsted, Seebeck, Ampère and others, while looking at Ohm’s mathematical treatise reveals the strong influence of Fourier. Perhaps most notable from Ohm’s work in this period is how readily he changed his conceptual approach. Over the course of three years, three distinct phases of work can be identified: in the first phase Ohm used a voltaic, or hydroelectric, pile and described his observations in terms of “loss of force”; in the second he replaced the unstable voltaic pile with a thermocouple and described his observations in terms of “exciting force”; and in the third he set aside his experimental work and focused instead on making mathematical arguments, shifting his language again to describe what was happening in an electrical circuit in terms of “electroscopic force”. The shift between Ohm’s first two phases of work can, this project argues, be made sense of by understanding changes in Ohm’s experimental setup and the way they affected his interaction with the phenomena he was studying. This thesis presents objects and instruments as integrated parts of the thought process of an experimenter, in which the apparatus shapes the thinking of the experimenter as much as the experimenter’s thoughts shape the design of the apparatus. This framework is then applied to Ohm’s work as a case study, leading to the suggestion that Ohm’s material interactions with his experiment shaped his conceptualisation of what was happening in an electrical circuit. It is possible to draw clear links between the conceptual tools and the material tools that Ohm used in his different phases of work; and, in understanding the practical experience Ohm had of using his apparatus, to make sense of his shifting use of language as he moved through different phases of work. Through its material-led approach, this project brings together history, philosophy and material culture of science in a single case study. It presents novel findings about Ohm’s work, uncovered through material engagement with his experimental setup, and offers a set of tools for material-led studies in the history of science.

Chang, Hasok
electricity, history of science, material culture, Ohm, philosophy of science, scientific instruments
Doctor of Philosophy (PhD)
Awarding Institution
University of Cambridge
AHRC (1517207)