DOCSLIB.ORG

Appendix a the Origins and Meanings of the Magnetic Force F

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Appendix a the Origins and Meanings of the Magnetic Force F Appendix A The Origins and Meanings of the Magnetic Force F = qv x B In Chapter 2 we showed that the electric component of Lorentz's force (FE = qE, with E = -\l4> - 8XIOt) had been utilized by Kirchhoff in 1857, although Kirchhoff did not speak in terms of electric fields. The magnetic vector potential X had been introduced by Franz Neumann in 1845. We also saw that B = \l x X, where B is the magnetic field. On the other hand the expression for the magnetic force had a later and more tortuous origin, and this is the subject of this appendix. We first discussed this topic in (Assis and Peixoto, 1992). The first relevant information to be stressed is that the expression for the magnetic force appeared after Maxwell's death (1879). According to Whittaker the first to arrive at the magnetic force were J. J. Thomson (1856-1940) and O. Heaviside (1850-1925), in 1881 and 1889, respectively (Whittaker, 1973, Vol. 1, pp. 306 to 310). One of the goals of Thomson's theoretical paper (Thomson, 1881) was to know how an electrified body is affected bya magnet. Thomson followed Maxwell's theory and in particular he utilized the idea that a displacement current (c8EIOt) produces the same effect as an ordinary conduction current 1, namely, a magnetic field B. He supposed a uniformly charged sphere moving in a certain medium with dielectric constant c and magnetic permeability Il, and calculated the displacement current at an external point Q. Then he calculated at another external point P the value of the vector potential X due to this displacement current in Q, and integrated over all points Q in space. But he then observed that the value of \l . X at this point P was different from zero. Maxwell, however, always assumed \l . X = O. Then to satisfy this condition Thomson supposed the existence of another component in X, adding this component to what he had obtained for X (he did not justify the physical origin of this extra component of X). Through B = \l x X he obtained the value of B at P. He then calculated the value of ii in this medium, Bill. Next he calculated the force exerted by a magnet (which generates B) on The Origins and Meanings 01 the Magnetic Force F = qv x B 239 a charged body which moves in this medium. To this end he calculated the interacting energy E = J J J(B. ii)2)dV, and utilized Lagrange's equations to get the force. His final result was ~ v x B F=q-- (Al) 2 This is half the present day value of classical electromagnetism. The most important aspect which we want to emphasize here is the meaning of the velocity which appears in (Al). Here Thomson was careful. He called this the "actual velocity" of the charge. On page 248 of his article he says: "It must be remarked that what we have for convenience called the actual velocity of the particle is, in fact, the velocity of the particle relative to the medium through which it is moving " ... , "medium whose magnetic permeability is /-t." This shows that to Thomson the velocity v in (Al) was not the velocity of the charge relative to the ether (as this medium and the earth might be moving relative to the ether without dragging it), nor relative to the magnet, and not either the velocity relative to the observer. Thomson extended his researches in this direction with a paper published in 1889 (Thomson, 1889). In 1889, in another theoretical paper, Heaviside obtained (Heaviside, 1889): F = qv x B . (A2) The main difference of his work from Thomson's 1S that he included, following Fitzgerald in 1881, the convection current as a source of magnetic field. In the other aspects he followed Thomson's work. He did not make any additional comment on the velocity v in (A2). So it can be assumed that for hirn as weIl this is the velocity of the charge q relative to the medium of magnetic permeability /-t and dielectric constant c. This is even more evident from the title of his paper: On the electromagnetic effects due to the motion of electrification through a dielectric. A discussion of the works of Thomson and Heaviside can be found in (Buchwald, 1985, Appendix I: Maxwellian Analysis of Charge Convection, pp. 269 - 277). 240 Appendix A In 1895, the theoretical physicist Lorentz presented the known expression (Lorentz, 1895; Pais, 1982, p. 125; and Pais, 1986, p. 76): F = qE + qv x B . (A3) Lorentz did not comment on the works of Thomson and Heaviside, and arrived at the magnetic part of this expression from Grassmann's force, substituting qv for I d~ although he did not mention Grassmann's work as weH. This can be seen in Lorentz most famous book, The Theory 01 Electrons (Lorentz, 1915, pp. 14 and 15). This book is based on a course he delivered in 1906 at Columbia University, which was edited for the first time in 1909. Unfortunately Lorentz did not specify in (A3) what is the object, medium or system relative to which the velocity v of the charge q is to be understood. As Lorentz still accepted MaxweH's ether (that is, a medium in astate of absolute rest relative to the frame of the fixed stars; see (Pais, 1982, p. 111)), it is natural to suppose that for him this was the velocity of the charge q relative to this ether, and not relative to any other medium or observer. In support of this statement we have Lorentz's own words on this same page 14: "Now, in accordance with the general principles of MaxweH's theory, we shall consider this force as caused by the state of the ether, and even, since this medium pervades the electrons, as exerted by the ether on all internal points of these particles where there is acharge" (Lorentz, 1915, p. 14). A conclusive proof of this interpretation can be found in another work of Lorentz: Lectures on Theoretical Physics (Lorentz, 1931, Vol. 3, p. 306; se also O'Rahilly, 1965, Vol. 2, p. 566). Here Lorentz says that if a wire carrying an electric current (and thus generating B), and a charge are at rest relative to the ether, then there will be no magnetic force. On the other hand if both share a common translation with velocity v relative to the ether (while the observer and the laboratory also translate with this same velocity v, because he gives as an example of this velocity that of the whole earth relative to the ether), then the says that there will be a magnetic force on the test charge. In this example there is no relative motion between the test charge and the current carrying wire, the observer, nor the laboratory, but only relative to the ether. On the other hand nowadays we utilize expression (A3) with v being the velocity of the charge q relative to an observer. This change of meaning happened after Einstein's The Origins and Meanings of the Magnetic Force P = qiJ x jj 241 work of 1905 on the special theory of relativity (Einstein, Lorentz, Minkowski and Weyl, 1952). In this work, after obtaining Lorentz's transformations of coordinates, Einstein applies them for the force (A3) and begins to utilize the velocity as being relative to the observer. For instance, on page 54 he gives (between square brackets are our words) the difference between the old paradigm of electromagnetism and the new one based on his theory of relativity: "Consequently the first three equations above [for the transformation of the field components in different inertial systems] allow themselves to be clothed in words in the two following ways: 1. If a unit electric point charge [q = 1] is in motion in an electromotive field, there acts upon it, in addition to the electric force [PE = qEJ, an "electromotive force" which, if we neglect the terms multiplied by the second and higher powers of v / c, is equal to the vector-product of the velocity of the charge and the magnetic force [.8], divided by the velocity of light [that is, PM = qv x .8 / c, so that the resultantforce is P = qE + qv x .8/ cl. (Old manner of expression). 2. If a unit electric point charge is in motion in an electromagnetic field, the force acting upon it is equal to the electric force [P' = qE'] which is present at the locality of the charge, and which we ascertain by transformation of the field [0 --t 0'] to a system of co­ ordinates [0'] at rest relatively to the electrical charge [iJ I = 0, so that qE+qiJx.8 /c = qE', where all magnitudes with ' refer to the fields in the system 0' which moves with velocity iJ relative to 0]. (New manner of expression)." It is instructive to see this conceptual change in one of the most utilized expressions of physics. It should be stressed that all of these works (Thomson, Heaviside, Lorentz, Einstein) were of a theoretical nature and realized after Maxwell's death. This change in the meaning of v in (A3) is very strange, confusing and unusual in physics. Appendix B Alternative Formulations of Electrodynamics In this book we dealt with mainly Weber's theory and classical electrodynamics (Maxwell's equations, Lorentz's force, retarded and Lienard-Wiechert potentials, etc.) In this Appendix we present some other approaches which have been proposed by some important scientists like Gauss, Riemann, Clausius and Ritz.
Load more

Recommended publications
  • Great Physicists
    Great Physicists Great Physicists The Life and Times of Leading Physicists from Galileo to Hawking William H. Cropper 1 2001 1 Oxford New York Athens Auckland Bangkok Bogota´ Buenos Aires Cape Town Chennai Dar es Salaam Delhi Florence HongKong Istanbul Karachi Kolkata Kuala Lumpur Madrid Melbourne Mexico City Mumbai Nairobi Paris Sao Paulo Shanghai Singapore Taipei Tokyo Toronto Warsaw and associated companies in Berlin Ibadan Copyright ᭧ 2001 by Oxford University Press, Inc. Published by Oxford University Press, Inc. 198 Madison Avenue, New York, New York 10016 Oxford is a registered trademark of Oxford University Press All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of Oxford University Press. Library of Congress Cataloging-in-Publication Data Cropper, William H. Great Physicists: the life and times of leadingphysicists from Galileo to Hawking/ William H. Cropper. p. cm Includes bibliographical references and index. ISBN 0–19–513748–5 1. Physicists—Biography. I. Title. QC15 .C76 2001 530'.092'2—dc21 [B] 2001021611 987654321 Printed in the United States of America on acid-free paper Contents Preface ix Acknowledgments xi I. Mechanics Historical Synopsis 3 1. How the Heavens Go 5 Galileo Galilei 2. A Man Obsessed 18 Isaac Newton II. Thermodynamics Historical Synopsis 41 3. A Tale of Two Revolutions 43 Sadi Carnot 4. On the Dark Side 51 Robert Mayer 5. A Holy Undertaking59 James Joule 6. Unities and a Unifier 71 Hermann Helmholtz 7. The Scientist as Virtuoso 78 William Thomson 8.
    [Show full text]
  • Pilgrimage Through the History of German Natural Science, University
    Pilgrimage through the History of German Natural Science, University City Bonn Kaoru Harada Kobe Shoin Women’s College, Sinoharaobanoyama-cho, Nada-ku, Kobe-city, 657-0015, Japan E-mail: [email protected] (Received 10 July 2001, Accepted 10 September 2001) Introduction scientists. The gravestone is a personal monument recording In the Roman days, Bonn was a citadel of Castra official and personal history. Visiting remains and various Bonnensia, and later the city of Bonn was a Teritory of the memorials of famous scholars gives me a satisfactory feeling. Archbishop of Koln for many years. In the year 1786, the The intellectual impression was quite different from that I got by University was established, but it was closed after 10 years. In reading a textbook dealing with the same subject, because grave the year 1818 a new University was established again in Bonn. visiting is a personal contact with historical person. I would like Since then, Bonn has been a University town. Therefore, to call such a visit a “pilgrimage” through the history of natural University of Bonn is relatively new in Germany as is the sciences. We may learn sciences through the pilgrimage, and University of Berlin (established 1810). But many famous also learn history through the pilgrimage. scholars have emerged from the University. The university is In this article, famous scientists are the main target of our officially called “Rheinisch Friedrich-Wilhelm-Universitat zu “pilgrimage”, however, some famous nonscientists are also Bonn” by the name of the founder. However, the organization is included because they are also contributors to our human history.
    [Show full text]
  • Questions for Science
    www.YoYoBrain.com - Accelerators for Memory and Learning Questions for science Category: Default - (50 questions) Who was Edward B. Taylor (1832-1917) - wrote some the founding texts in anthropology and held Oxford University's first position in anthropology Who was Lewis Henry Morgan (1818-1881) pioneered anthropology in United States Who was Franz Boas (1858-1942) founded modern American anthropology and provided enduring principle of cultural relativity Who was: Bronislaw Malinowski (1884-1942) Polish born, studied in Austria; studied the Trobriand islanders off the east coast of New Guinea. Who was Margaret Mead (1901-1978) became the public face of anthropology. She studied the Somoan society and published her findings in Coming of Age in Samoa. Who is Richard Dawkins sociobiologist who coined the phrase "the selfish gene" Who was Benjamin Lee Whorf (1897-1941) a part time linguist (anthropology) and fire insurance investigator who developed hypothesis around how language structures the way we look at things. Who was Claudius Ptolemy 2 AD - ancient Greek astronomer and geographer. Wrote Almagest which was a treatise on astronomy that put Earth at center of universe. Wrote Geography which was a compilation of everything known about geography in Roman empire Who was Antoni van Leeuwenhoek (lay' ven huk) (1632-1723) Man who first discovered microbes by developing microscopes What is the Coppenhagen interpretation of nature, at the most fundamental level, is quantum mechanics probabilistic, not deterministic Define: use of spectrometer identifies the frequencies of light Define: use of interferometer allows scientists to measure extremely small distances What did the color-corrected microscope enabled high-power magnification without allow scientists to do blurring Define: dynamism the notion that change is a normal state What 3 papers did Einstein write in 1905 1.) paper on Brownian motion where he convinced many of reality of atoms 2.) photoelectric effect - explained the phenomenon that certain materials that when exposed to light, give off electrons.
    [Show full text]
  • 18. the 2Nd & 3Rd Laws of Thermodynamics
    18. The 2nd & 3rd Laws of Thermodynamics Introduction and Summary The oldest statement of the 2nd Law comes from the German physicist and mathematician Rudolf Clausius. He said that "heat can flow spontaneously from a hot object to a cold object; heat does not flow spontaneously from a cold object to a hot object." (P.416 Giancoli and also http://en.wikipedia.org/wiki/Second_law_of _thermodynamics) At first glance, this appears to be a restatement of the 0th Law but it is in fact a little different. Heat can be made to flow from a cold object to a warm object--for example, in a refrigerator or with an air conditioner. However, this does not happen spontaneously--that is, by itself--since work must be done for this to happen. The 2nd Law is a little strange since it is a statement about something that does not happen. 2 18. The 2nd & 3rd Laws of Thermo dynamics Rev2.nb Another statement of the 2nd Law, made by the English physicist Lord Kelvin, is that a quantity of heat Q cannot be converted entirely into work W. 18. The 2nd & 3rd Laws of Thermo dynamics Rev2.nb 3 Some of the heat must leave the engine and be expelled into the environment as waste heat. Since efficiency equals the work done divided by the heat put in, the 2nd Law says a heat engine cannot be 100% efficient. It is perhaps surprising, that if you assume the Clausius statement of the 2nd Law is true, then you can prove that the Kelvin statement is also true and vice-versa.
    [Show full text]
  • Thermodynamics of Life
    Firenze University Press www.fupress.com/substantia Research Articles Thermodynamics of Life Citation: Henry M. (2021) Thermodynam- ics of Life. Substantia 5(1) : 43-71. doi: Marc Henry 10.36253/Substantia-959 Laboratoire de Chimie Moléculaire de l’Etat Solide, UMR 7140, Université de Strasbourg, Received: Jun 02, 2020 France E-mail: [email protected] Revised: Aug 25, 2020 Just Accepted Online: Aug 26, 2020 Abstract. Biology is currently plagued by several fossil concepts that may be responsi- ble for the current stagnation in medicine. Through a careful screening of the origins Published: Mar 01, 2021 of thermodynamics, such fossils concepts have been identified: assumption that heat is Copyright: © 2021 Henry M. This is an a form of energy, assimilation of entropy to disorder, assimilation of death to states of open access, peer-reviewed article maximum entropy, assimilation of ATP to the energy currency of living cells, non-rec- published by Firenze University Press ognition of entropy as a state function of the whole universe, belief that free energies are (http://www.fupress.com/substantia) another kind of energy, self-referencing in the definition of life, ignorance of basic princi- and distributed under the terms of the ples of quantum physics and more particularly of the importance of intrinsic spin, confu- Creative Commons Attribution License, sion between three different forms of reversibility, non-recognition that irreversibility is which permits unrestricted use, distri- at the heart of living systems. After stowing of these concepts in the cabinet of useless bution, and reproduction in any medi- um, provided the original author and and nasty notions, a fresh new look is proposed showing how life is deep-rooted trough source are credited.
    [Show full text]
  • Conceptualizing Energy
    EHIND B TH Y E Conceptualizing Energy R S O C T I Conservation of Mechanical Energy E S N E C E H and the Introduction of Potential Energy T William Thomson Most students who have taken high school chemistry or century, many French engineers had realized that the total physics know the First Law of Thermodynamics: “Energy work a moving body could perform was equal to half of its can neither be created nor destroyed.” But at the vis viva.These engineers redefined “work” as ½ mv2 . beginning of the nineteenth century, physicists had not yet formulated this fundamental law of nature. Moreover, at One of the most important French engineers of the early this time the term “energy” did not have a precise scientific nineteenth century was a man named Sadi Carnot (1796- definition, and most physicists thought matter and force 1832). As a young man, Carnot watched his home country were the only concepts needed to understand the natural lose the Napoleonic Wars to England. He was convinced world. that England's military superiority was due entirely to its industrial superiority, in particular its steam engines. The idea that mechanical energy is conserved and the Carnot became interested in how France could improve its introduction of potential energy transformed the study of own steam engines, and began thinking about the physics energy into one of the most important and exciting areas of behind the way engines worked. nineteenth-century physics. But assigning credit for developing these principles is difficult. The great Scottish ! physicist William Thomson (1824-1907) is generally given Science and technology are not the same, but credit for stating the first law, but to do so he drew on the they do significantly impact one another.
    [Show full text]
  • The Concept of Entropy, from Its Origins to Teachers
    EDUCATION Revista Mexicana de F´ısica E 61 (2015) 69–80 JULY–DECEMBER 2015 The concept of entropy, from its origins to teachers F. Flores Camachoa, N. Ulloa Lugob, and H. Covarrubias Mart´ıneza aCentro de Ciencias Aplicadas y Desarrollo Tecnologico,´ Universidad Nacional Autonoma´ de Mexico,´ 04510 Mexico,´ D.F., Mexico.´ bFacultad de Estudios Superiores-Iztacala, Universidad Nacional Autonoma´ de Mexico,´ 54090 Tlalnepantla, Edo. de Mexico,´ Mexico.´ Received 10 April 2015; accepted 3 June 2015 Research on alternative conceptions shows that the entropy concept is among the most difficult for students to understand. Entropy is a concept with a complex history and has been the subject of diverse reconstructions and interpretations. This paper presents a brief review of the origin of the concept (Clausius and Boltzmann), a description of some influential textbooks (Planck, Fermi and Gibbs) and a comparative review on textbooks and how the concept of entropy is conceived and taught by university teachers. The results show that there is a great variety in the descriptions and meanings of entropy provided in textbooks, confusing students and teachers. A brief discussion focuses on new conceptual approaches to entropy. We conclude by suggesting how history can contribute to teachers and students’ awareness about changes in the meaning of entropy and their acceptance of a more relevant commitment in their understanding of physical concepts. Keywords: Entropy in education; science in school. PACS: 01.40 E-; 01.40.fk 1. Introduction persion in its conceptualization. Considering all of these fac- tors, we can formulate some questions: What remains of the At virtually all education levels, research on thermodynamics original interpretations of entropy and its historical develop- concepts indicates that students have difficulties understand- ment? How have original ideas of entropy been transformed ing them.
    [Show full text]
  • Theory of Electricity by Rudolf Clausius in the Development of Thermodynamics
    Eri Yagi and Rika Tadokoro Theory of Electricity by Rudolf Clausius in the Development of Thermodynamics Abstract Clausius’s four papers (1852-57) on the theory of electricity are analyzed by the help of our own database. These papers are classified by him under the mechanical theory of heat together with his papers on thermodynamics and gas theory. The first law and the essential part of the second law of thermodynamics were established in his first Abhandlung (1850). The first law is applied to these four papers on the theory of electricity, where heat, produced by electricity, is considered as the equivalent with the mechanical work. The essential part of the second law is applied to the 12th paper on thermoelectric current. The current between two different metals is treated by the similar method to heat flow. Here the temperature dependence is expressed as dt/C which is the maximum work of the infinitesimal Carnot cycle. 1. Introduction R. Clausius’s published papers, books (1847-85) and his manuscripts at the Library of the Deutsches Museum were studied,9-16 and the role of his papers on the theory of electricity was made clear. The so called “Clausius’s mechanical theory of heat” (die Mechanische Waermetheorie) consists of three fields, e.g., thermodynamics, the theory of electricity, and gas theory. Two volumes of his collected papers, compiled his 16 papers.1 Among these 16 papers, the 1st to the 9th papers (1850-65) are on thermodynamics, the 10th to the 13th papers (1852-7) on the theory of electricity, and the 14th to the 16th papers (1857-62) on gas theory.2 Clausius presented the first law of thermodynamics in his first paper on the mechanical theory of heat in 1850,2(I) in the differential form.
    [Show full text]
  • Infografik Als PDF Herunterladen
    beginnt seine publiziert „Über die Erhaltung tritt Physiologie- Ausbildung schließt seine der Kraft“ (1. Hauptsatz der Professur als Militärarzt Doktorarbeit über die Thermodynamik) Helmholtz und seine Zeit in Königsberg an. Nervenfasern ab 1847 Das 19. Jahrhundert ist geprägt von wissenschaftlichem, 1838 heiratet technischem und industriellem Fortschritt, aber auch von arbeitet als Chirurg an Olga von Velten der Charité und dient bis Krisen. Unsere Infografik zeigtHelmholtz� Meilensteine Hermann 1848 als Militärarzt in 1849 und die seiner Weggefährten. Helmholtz Potsdam und Berlin wird in Potsdam geboren 1842 31.08.1821 1848/49 Deutsche Revolution hermann 1845 1820 Gründung der Physikalischen Gesellschaft zu Berlin Hans Christian Ørsted (heute Deutsche Physikalische 200 jahre 1847 1804 entdeckt den Gesellschaft (heute: DPG)) Helmholtz Elektromagnetismus Werner Siemens und Johann Halske Richard Trevithick gründen die Telegrafenanstalt (Ursprung der Firma Siemens) erfindet die Dampflokomotive tritt Physiologie-Professur publiziert zu Wirbel bewegungen in Bonn an in Flüssigkeiten publiziert „Die Lehre von den Tonempfindungen“ 1855 baut einen Apparat zur Bestimmung von Klangfarben 1863 (= erster Synthesizer) Tod seiner Frau Olga konstruiert den Augenspiegel entwickelt die publiziert Handbuch tritt Physiologie-Professur 1859 heiratet misst als erster die publiziert Theorie Dreifarbentheorie der physiologischen in Heidelberg an Anna von Nerven leit geschwindigkeit der Elektrodynamik Optik Mohl 1852 1858 1850 1856 1861 1870 1867 1870/71 Karl Marx 1867 Deutsch-französischer Krieg 1858 1860 publiziert 1859 „Das Kapital“ Werner Siemens Louis Pasteur Rudolf Virchow 1864 entdeckt das dynamoelektrische entwickelt Theorie der Charles Darwin weist nach, dass Mikro- 1850/51 Julius Lothar Meyer Prinzip und begründet damit Zellularpathologie publiziert organismen die Ursache Rudolf Clausius und William Thomson Evolutionstheorie vieler Erkrankungen sind entwickelt das Periodensystem die moderne Starkstromtechnik.
    [Show full text]
  • Physics and Philosophy  Issn: 1863-7388  2007  Id: 008
    Physics and Philosophy Issn: 1863-7388 2007 Id: 008 Article The Controversial Universe: A Historical Perspective on the Scientic Status of Cosmology Helge Kragh (Steno Institute, University of Aarhus, Denmark. E-mail: [email protected]) Abstract: The domain of cosmology is the universe, a singular concept, and basically for this reason cosmology is a science that diers from other sciences. For a long time there have been critical voices which argue that cosmology cannot be a proper science on par with, say, nuclear physics or hydrodynamics. This kind of critique goes a long way back in time, and I review it here in a historical perspective, focusing on the century from 1870 to 1970. I suggest that there are no good reasons to deny cosmology the status of a proper science. On the other hand, I also consider it natural, and a sign of health, that such foundational questions continue to be part of the cosmological discourse. Keywords: Cosmology, history of modern cosmology, science, universe, Kant 1 During the last fty years or so, cosmology has developed greatly and is today recognized to be a mature and fundamental part of the physical sciences. With the Nobel prizes in physics awarded in 1978 and 2006 to work related to big- bang cosmology it may seem pointless to argue that cosmology is not a proper science. After all, it is hard to imagine that Nobel laureates in physics should earn the prize for doing work that doesn't even qualify as science. It is generally recognized, often with a considerable measure of self-congratulation, that The discovery of the cosmic microwave background in the 1960s established the big bang theory and made cosmology into an empirical science, such as stated in an article in Scientic American from 1992 (Brush 1992, p.
    [Show full text]
  • Die Idee Des Humanen Rudolf Virchow Und Hermann Von Helmholtz
    Der Reichskanzler der Physik: Leben und Wirken von Hermann von Helmholtz Es ist Kaiser Wilhelm I., der im Jahre 1883 den 1821 in Potsdam gebo­ renen Hermann Helmholtz in den Adelsstand erhebt, kurz nachdem der als Mediziner ausgebildete, als Sinnesphysiologe erfolgreiche, als Philosoph beeindruckende, als Physiker überragende und sich in vie­ len populär gehaltenen Schrifen um die Vermittlung seines Wissens­ schatzes bemühende Universalgelehrte zusammen mit Industriellen und Freunden eine Denkschrif verfasst hat, in der vorgeschlagen wird, ein »Institut für die experimentelle Förderung der exakten Naturfor­ schung und Präzisionstechnik« zu gründen. Das Vorhaben kann mit Erfolg durchgeführt werden und hat die berühmte Physikalisch­Tech­ nische Reichsanstalt entstehen lassen, zu deren erstem Präsidenten der preußische Staat 1887 den verehrten Bildungsbürger und Kulturträger Hermann von Helmholtz beruf. Ihm wird dafür sogar ein exorbitan­ tes Salär zugebilligt, dessen Höhe Helmholtz selbst vorgeschlagen hat. Die Physikalisch-Technische Reichsanstalt (jetzt: Physikalisch-Technische Bun- desanstalt) wird 1887 auf maßgebliche Initiative von Werner von Siemens in Berlin gegründet. Hermann von Helmholtz ist ihr erster Präsident. 122 Er meint, dass ihm dies als »Reichskanzler der Physik«, wie er in An­ spielung auf Bismarck von seinen Kollegen respektvoll genannt wird, zustehe. Schließlich habe er eine Gelehrtenrepublik zu regieren wie der Reichskanzler seine Nation, und tatsächlich beklagt sich niemand über die Besoldung des Präsidenten. Man betrachtet sie wohl als angemessen angesichts des Arbeitspensums, das Helmholtz als Leiter der großange­ legten Institution zu bewältigen hat. Unter seiner Leitung führen Wis­ senschafler eine Fülle von Forschungsarbeiten durch, um den Einsatz von Elektrizität zu erproben oder zu einem besseren Verständnis von Wärme und Licht zu gelangen.
    [Show full text]
  • 1 Introduction to Energy
    Corso di Laurea in FISICA Basic on the physics of energy transformaons at micro and nanoscales Luca Gammaitoni ICT-Energy Summer school 2016, Aalborg Prof. Luca Gammaitoni University of Perugia (IT) AD 1308 Florence Roma Perugia 4 Lectures 1) Introduction to energy 2) Energy transformations at micro scales 3) The physics of computing: fundamental limits on energy 4) Energy dissipation in present ICT devices Corso di Laurea in FISICA 1 Introduc2on to energy Luca Gammaitoni ICT-Energy Summer school 2016, Aalborg Corso di EnergyLaurea in FISICA What is it? Corso di EnergyLaurea in FISICA In physics, energy (Ancient Greek: ἐνέργεια energeia "activity, operation”) is an indirectly observed quantity that is often understood as the ability of a physical system to do work on other physical systems Capability of doing WORK… WORK = FORCE x Displacement Corso di EnergyLaurea in FISICA In physics, energy (Ancient Greek: ἐνέργεια energeia "activity, operation”) is an indirectly observed quantity that is often understood as the ability of a physical system to do work on other physical systems Capability of doing WORK… WORK = FORCE x Displacement Energy ? Energy ? Energy ? Corso di EnergyLaurea in FISICA "It is important to realize that in physics today, we have no knowledge what energy is." Richard Feynman, in The Feynman Lectures on Physics (1964) Volume I, 4-1 Energy: a hint of history The vis viva (living force), which Goried Leibniz defined as the product of the mass of an object and its velocity squared; he believed that total vis viva was conserved. To account for slowing due to fric2on, Leibniz theorized that thermal energy consisted of the random moon of the constuent parts of maer, a view shared by Isaac Newton, although it would be more than a century un2l this was generally accepted.
    [Show full text]