The Experimental and Historical Foundations of Electricity - Unicamp

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Chapter 3 The Versorium 3.1 Fracastoro’s Perpendiculo andGilbert’s Versorium We will now discuss the oldest electrical instrument. It was created by Girolamo Fracastoro(1478-1553)(Figure3.1). SomegivehisnameasFracastoro, othersas Fracastorio. 1 He was a poet, physician, and philosopher in Verona. 2 Fracastoro is better known for his works on medicine, especially epidemiology. He gave the name syphilis to a known venereal disease. 1 [Ben98, p. 241]. 2 [Zan81]. Figure 3.1: Girolamo Fracastoro (1478-1553). 33
His instrument was first presented in a book published in 1546. 3 He utilized ittoshowthatrubbedamberattractsnotonlystrawsandchaff, butalsoanother piece of amber, and even a metal like silver. He also discovered that diamond has the property of attracting light substances after being rubbed, as is the case with amber. Fracastoro describes his new instrument with the following words: 4 In fact we, in the presence of several of our medical doctors, have mademanyexperimentswithaperpendiculowhichiswelladaptedas in a marine compass, and have observed how a magnet attracts another magnet, [magnetized] iron [attracts] iron, due to the fact that a magnet attracts iron and the iron [attracts] the magnet; moreover, [rubbed] amber snatches up little pieces of amber... and, likewise, [rubbed] amber attracts to itself not only straws and chaff, but also silver. When he writes perpendiculo, Fracastoro might be referring to a plumb line, 5 i.e., a small object suspended by a vertical thread from a support, like a pendulum. The thread would be free to move in any direction around the point to which it is attached. The word “perpendiculo” is connected with “perpendicular,” which means a straight line at right angles to the horizon. A plumb line is utilized to indicate a vertical direction. For this reason it is natural to suppose that Fracastoro’s perpendiculo was analogous to a plumb line. From description above we infer that Fracastoro attached a small piece of amber or silver to the end of the thread. When he brought a rubbed amber near the perpendiculo, he would have observed that it departed from the vertical direction, moving closer to the rubbed amber (Figure 3.2). The advantage of the perpendiculo in comparison with straws or chaff; is that the tension of the thread conterbalances the weight of the suspended body. It is then easy to see its motion in a horizontal direction even for a small attractive force. On the other hand, if the small piece of amber or silver was on a table, it would have been more difficult to observe or detect any motion due to its weight. That is, it would be difficult to see its vertical motion toward a rubbed amber placed near it. Gilbert knew Fracastoro’s book and quoted it several times in his book: 6 3 [Gli33] and [Hei99, p. 175]. 4 “Nos enim praesentibus multis è nostris medicis experientiam multorum secimus, perpendiculo bene & concinne aptato, quale est in nauigatoria pyxide, ac manifeste vidimus magnete trahere magnete, ferrum ferrũ, tum magnetem trahere ferrum, ferrum magnetem porro electrum parua electri frustula rapere, argentum attrahere argentum, &, quod valde inirati fui mus, magnetemvidimusargentumtrahere: itemElectrumnonsolumfurculos&paleasmouere ad se, sed & argentum,” [Fra55, p. 85 verso]. In Italian: “Noi infatti alla presenza di molti dei nostri medici facemmo esperienza di molte cose con un perpendiculo bene e convenientemente adattato come è nella bussola da navigare e vedemmo manifestamente che il magnete attrae il magnete, il ferro il ferro, poi che il magnete attrae il ferro e il ferro il magnete; e ancora, l’ambra rapisce pessettini d’ambra... e parimenti l’ambra non avvicina solamente a sè i fuscelli e le pagliuzze, ma anche l’argento,” [Gli33]. 5 [Sas02]. 6 [Gil78, pp. 28-29]. 34
Page 1 and 2: Andre Koch Torres Assis The Experim
Page 3 and 4: Published by C. Roy Keys Inc. 4405,
Page 5 and 6: 4.8 The ACR Mechanism . . . . . . .
Page 7 and 8: Bibliography 259 6
Page 9 and 10: GGPE—UNICAMP, as well as the rich
Page 12 and 13: Chapter 1 Introduction One of the g
Page 14 and 15: even be utilized at a post-graduate
Page 16 and 17: Chapter 2 Electrification by Fricti
Page 18 and 19: which does not attract small pieces
Page 20 and 21: Accordingtosomemodernauthors, theam
Page 22 and 23: never be rubbed. This will be our n
Page 24 and 25: Experiment 2.6 Figure 2.5: A rubbed
Page 26 and 27: I opened the cock, and let the wate
Page 28 and 29: Or else: 20 Andlikenessisnotthecaus
Page 30 and 31: (a) (b) F F F F F (c) . F F F F F F
Page 32: Several words used to this day have
Page 37 and 38: Figure 3.3: Gilbert’s versorium.
Page 39 and 40: in this case a strip of plastic or
Page 41 and 42: with a light mobile part made of a
Page 43 and 44: (a) (b) F F F F F F F F F F Figure
Page 45 and 46: Experiment 3.3 We move a neutral st
Page 47 and 48: circles coinciding with the center
Page 49 and 50: hour. The experiments indicate that
Page 51 and 52: The fact that an electrically charg
Page 53 and 54: Figure 3.20: Robert Boyle (1627-169
Page 55 and 56: This course of rubbing on the edge
Page 57 and 58: follows: 21 To every action there i
Page 59 and 60: hitherto escape observation; and pe
Page 61 and 62: thread 10 or 20 cm long. The thread
Page 63 and 64: 4.2 Guericke’s Experiment with a
Page 65 and 66: It appeared in his book The New (So
Page 67 and 68: and Roller, Krafft, and Heilbron. 4
Page 69 and 70: F C FC F (a) F F F (d) F F F C C (b
Page 71 and 72: to note that Du Fay himself did not
Page 73 and 74: A very practical support can be mad
Page 75 and 76: F F F F F F F F F F (a) (b) Figure
Page 77 and 78: Definitions: We say that in Experim
Page 79 and 80: At this moment we move the finger s
Page 81 and 82: Experiment 4.11 We rub a plastic st
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4.8 The ACR Mechanism In 1733 Du Fa
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Experiment 4.15 We can make the ele
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It is simply a cotton or linen thre
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to 0.5 cm, and the maximum dimensio
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(a) (b) F F F F F F F F F F F F F F
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Now what farther I have to add, occ
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Chapter 5 Positive and Negative Cha
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first neutral pendulum. The pendulu
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I A PA A SA A A A A II (a) (b) Figu
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charged pendulum �, without allow
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straw that has been rubbed with an
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+ + + - - - + + + - - - (a) (b) (c)
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[...] It is then certain that bodie
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I confess I had expected an entirel
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A very interesting video showing a
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same happens between a plastic rubb
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two charged pendulums hang vertical
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- - - + + + - - - + + + (a) (b) (c)
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electricity. Initially he built a m
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charged straws, we can determine th
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+ hair smooth glass human skin synt
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now slowly bring our finger near th
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whichchargeditbycontact. Inthissitu
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electrified than �, that is, that
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the level of the thermometer is hig
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Chapter 6 Conductors and Insulators
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is to fold the upper strip horizont
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- - - (a) (b) (c) . Figure 6.5: (a)
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toward the electroscope and away fr
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(a) (b) Figure 6.10: Attraction bet
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Experiment 6.11 We again charge the
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Experiment 6.13 The procedure descr
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are conductors, very few are insula
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Experiment 6.15 The procedure of Ex
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conductor insulator (a) (b) (c). in
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second wire is connected to the pos
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suppose that the light does not tur
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6.7.1 The Time Necessary in order t
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pendulum negatively and another one
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- - - (a) - - - - - - - - - (b) - -
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(a) (b) Figure 6.32: (a) Electrosco
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it was prick’d, and the snapping
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pended by silk cords, presents the
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Figure 6.36: Nollet’s electromete
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od �, with a cork ball at the end
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Chapter 7 Differences between Condu
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the pendulums and electroscopes als
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the disk. plastic straw disk of thi
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all of them placed side by side on
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- - - - - - - - - - � � � �
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them side by side along the same pl
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sides, provided the plate is polari
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An experiment analogous to Experime
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(a) (b) Figure 7.17: Two electrosco
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trically polarized. The edge close
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it charges a pendulum by the ACR me
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move the rubbed straw near the cond
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- - - (a) (b) Figure7.26: (a)Aninsu
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� � � � � � � � Fig
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- - - - - - - - - - � � � �
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to distinguish it from the polarize
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net negative charge of ��. The
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of opposite sign attract one anothe
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Figure 7.38: W. Thomson (Lord Kelvi
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- - - - - - - - - - - - - - - - - -
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amber effect, Sections 2.1 and 2.2.
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Figure 7.44: We strike a match near
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F F F F F F (a) (b) Figure 7.45: (a
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Chapter 8 Final Considerations 8.1
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forces also increases when the stre
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ordinary experiments involving smal
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the plastic disk. This polarization
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The microscopic description of what
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+ + + + - - - - + - + - --- + - + -
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Appendix A Definitions Here we pres
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Appendix B Stephen Gray and the Dis
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attractive vertue might be carried
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was attracted and repelled many tim
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this article: to communicate electr
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making metals attract light bodies.
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greatest discovery: 21 As we had no
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Figure B.9: Gray rubs his 1 m long
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Grayhadalreadydiscoveredhowtocommun
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A representation of this experiment
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March the 23d [of 1730], I dissolve
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Figure B.19: Illustration of Du Fay
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estimation, about fourteen or fifte
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In Section 4.10 we analyzed the beh
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Bibliography [Aep79] F. U. T. Aepin
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[Can54] J. Canton. A letter to the
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[Fer01c] N. C. Ferreira. Magnetismo
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[Haub] F. Hauksbee. An account of t
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[Ørs98a] H. C. Ørsted. New electr
Page 270:
The Experimental and Historical Fou
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