FIG 1 - uploaded by Elizabeth Cavicchi
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In the 1830s, American experimenter Charles Grafton Page pioneered electromagnetism, developing instruments, experimental practice, and understandings that were foundational for nineteenth-century technologies such as the telegraph and induction coil. While a student, Page detected electricity in a spiral conductor where direct current had not pass...
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... either assembled or learned to use during my proj- ect. Just as Page started from materials that were on hand, similarly, I started with items readily accessible today. Page constructed an electrical analog to Henry's spiral out of copper sheet; I devised an analog to Page's spiral from copper tape intended as edging for panes of stained glass ( fig. 10). This con- ductive foil spirals outward in an unbroken path; its paper backing insulates successive turns from each other, similar to the effect of Page's fabric. At intervals along the spiral, I soldered copper strips like Page's cup supports. In place of mercury cups, I used alligator clips to connect my spiral to other apparatuses. ...
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... analog to the function that Page's body played in detecting electric- ity, I used a storage oscilloscope. 41 This instrument displays the signal volt- age picked up by its probes as a trace on a two-dimensional screen, where voltage is on the vertical axis and time is on the horizontal one ( fig. 11). As the trace is repeatedly redrawn across the screen, its excursions up and down indicate changes in voltage occurring during the time interval repre- sented by the horizontal axis. This timescale can be varied across many orders of magnitude, as can the voltage scale applied to the vertical axis. Signals that are stable in voltage ...
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... typical trace produced within my spiral showed a voltage spike of sev- eral hundred volts, followed by lesser peaks spaced microseconds apart ( fig. 11, right). Treating this trace as a proxy for Page's sense of shock, I inter- preted traces showing greater excursions in voltage as representing circum- stances whereby Page might have reported greater ...
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... with these materials, I followed Page's practice by connecting a battery across part of the spiral and putting the oscilloscope probes across that same part, or some other part ( fig. 12, left). Upon disconnecting the battery, I observed the trace and noted its peak value. Then I changed the connections, switched the battery on and off, and observed the next trace. In the first phase of my project, I sketched these traces by hand; later, I used a digital-storage oscilloscope to save each trace into a computer file for later ...
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... I looked into various measure- ments and models of the human body's electrical properties. 43 The simplest model represents the body as posing a resistance to the flow of current. This resistance is high for dry skin, low for tissue. To simulate this, I insert- ed an electrical resistor into my circuit, across the oscilloscope probe ( fig. 12, right); 44 still, the voltage did not always increase where I expected it to, and it was confusing to remember and compare subsequent ...
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... my data collection: values of voltage and time saved from more than one trace could be plotted on the same axes, allowing a direct overlay comparison among traces taken in different trials. I used this method to compare the trace produced when a low-val- ued resistor was in the circuit (like Page's body) with a trace produced without one ( fig. 13, left). With the low resistor, the trace exhibited one major peak-without the declining oscillations that characterize the trace taken from that same circuit without the ...
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... resistor affected the shape of the electrical signal when it was included in the circuit, suggesting that the body plays an active part in the circuit. The single spike of this resistor test corroborated with the narrow- spike trace that resulted when a human volunteer put himself into my spi- ral circuit where the resistor had been ( fig. 13, right). However, while I found that the human body affects the circuit, further tests showed that its inclusion (through an electrical substitute) did not remove the ambiguity that motivated my questions. I still lacked a consistent demonstration of voltage increase when the probe covers more of the spiral's length. 47. For more description ...
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... of traces that were produced when I changed nothing in the experiment's connections, but repeatedly closed and opened the switch that lets battery current into the circuit, under what I thought were identical conditions. When I superposed on one plot these traces taken from successive switching events, their peak values varied over a wide range (fig. 14, left). This pronounced variability contrasts sharply with the repeatable signals put out by my iron-core coils when I activated them using the same battery and ...
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... tures of the oscilloscope and software that were unfamiliar to me. These techniques opened up multiple views on what was going on within my spi- rals, just as, to him, Page's intermediate taps opened up the spiral's internal electricity. In some of these experimental contexts, I observed voltages in- crease in accord with what Page reported ( fig. 14, right). 49 Such confirmatory findings do not end my exploration. There are al- ways more ways to probe the spiral and analyze its variable signals. The observation that ambiguities remain, even under examination by diverse techniques, indicates how ambiguities-including those from the human body-are intrinsic to experimenting. Ambiguity ...
Citations
... Despre experimentele lui Henry află și fizicianul și profesorul de chimie Charles Grafton Page (1812-1862) în anul 1836 [6]. Page, un inventator neobosit, introduce noi tipuri de experimente în care fenomenele electrice studiate sunt puse în evidență prin șocurile electrice produse în corpul uman, fapt care reflectă practicile comune și des utilizate pentru observarea electricității produse în baterii la acea vreme. ...
... Fig. 5. Măsurarea șocului electric: a) experimentul lui Henry cu fir și cu bobină plată spiralată; b) experimentul lui Page, cu procedeul de preparare a foliei de cupru si cu dispunerea ploturilor de măsurare; după [6] Page realizează o bobină spiralată folosind materialele la îndemână ( Fig. 5.b). În lipsa unei benzi adecvate de cupru pentru formarea bobinei spirale, el a construit dispozitivul cu benzi din foi plate de cupru. ...
... Cu ploturile plasate intermediar, același conductor putea suporta curenți pe toată lungimea sau pe o parte din lungime lui ( Fig. 5.b). În lucrarea [6], în care se explorează începutul dezvoltării bobinei de inducție la sfârșitul anilor 1830, se aduc completări legate de dispozitivul propus de Page (Fig. 6). șocul electric este pus în evidență între ploturile 3 și 4 (apoi, succesiv, 5, 6), după [6] Șocul și scânteia electrică din ce în ce mai puternice produse în astfel de bobine au constituit un feedback pentru numeroasele configurații instrumentale propuse şi testate de Page, Callan, Sturgeon, Bachhoffner și alții. ...
The transformer is the equipment that revolutionized the long-distance transmission of electrical energy. Many of the applications of electricity are related to this electrical equipment, which has been designed and perfected through the contributions of numerous experimenters, scientists, engineers, and technicians over two hundred years of creative efforts. This work synthesizes the stages of accumulation of scientific and technical knowledge in electromagnetism, which led to the patenting and construction of the first electrical transformer in 1884-1885. In addition to the chronological milestones of the genesis of the electrical transformer, the contributions made by this equipment to the inauguration of a new stage in the development of human society based on comfort and productivity are also illustrated. The new directions of research and development in which sustainability is the key element show that the electrical transformer will not remain just an artifact preserved in museums.
... Anomalies or unexpected behaviors attract historical experimenter's intereest, giving rise to new investigations and observations that branch out by nonlinear paths (Gooding, 1990;Holmes, 2004;Steinle, 1997). Studies conducted by historians to replicate historical experiments come upon yet other kinds of observations and investigative paths (Cavicchi, 2006a(Cavicchi, , 2008aHeering, 1994;Sibum, 1995;Staubermann, 2007;Tweney, 2006). ...
A teacher and a college student explore experimental science and its history by reading historical texts, and responding with replications and experiments of their own. A curriculum of ever-widening possibilities evolves in their ongoing interactions with each other, history, and such materials as pendulums, flame, and resonant singing tubes. Narratives illustrate how questions, observations, and developments emerge in class interactions, along with the pair’s reflections on history and research. This study applies the research pedagogy of critical exploration, developed by Eleanor Duckworth from the interviewing of Piaget and Inhelder and exploratory activities of the 1960s Elementary Science Study. Complexity as the subject matter opens up possibilities which foster curiosity among participants. Like Galileo, Tyndall, Xu Shou, and others, this student recurrently came upon new physical behaviors. His responses to these phenomena enabled him to learn from yet other unexpected happenings. These explorations have implications for opening up classrooms to unforeseen possibilities for learning.
Teaching . . . is more about a conscientious participation in expanding the space of the possible by creating the conditions for the emergence of the not-yet-imaginable. . . . Teaching, like learning, is not about convergence onto a pre-established truth, but about divergence - about broadening what can be known and done. In other words, the emphasis is not on what is, but what might be brought forth. Teaching thus comes to be a participation in a recursively elaborative process of opening up new spaces of possibility while exploring current spaces. (Davis & Sumara, 2007, p. 64)
Until the twentieth century, fundamental discoveries of electricity were experienced and articulated by integrating the living and dead flesh of human and other animal bodies into electrical circuits. Examples of this include Watsons flying boy capacitors, Galvani's frog motors, Franklins batteries, Volta's pile, Pages' inductors, Meuccis telephone and Grays musical telegraph. Public demonstrations of electrified bodies were largely abandoned in the early 1900s as electrical engineering professionalized, power levels increased, electrocutions terrified, and doctors prohibited. The production of electrosomatophones, musical instruments that incorporate electricity in human bodies for sound production, was not slowed by the establishment of this taboo against direct human contact with the electrical fire, but the taboo did induce a significant change in practice: a shift away from direct current flows through bodies to electrical field modulations of the bodyas typified by the Theremin of 1920 and musical instrument apps that use the touch screens of todays mobile telephones. Visceral experience of electricity is attenuated by this move to very low currents and electric field interactions. The resulting mystification profoundly reconfigured and conditioned embodied and encultured knowledge of electricity. These changes will be critically examined by surveying the practice and discourse of the last 300 years of electrosomatophone development including the Denis dor of Vclav Prokop Divi in 1748, Grays devices of the late 1800s, Theremin in the early 1900s, Eremeeff, Trautwein, Lertes, Heller in the 1930s, Le Caine in the 1950s, Michel Waisvisz and Don Buchla in the 1960s, Salvatori Martirano and the Circuit Benders in the 1970s, and Smule Inc. in this decade.
