DOCSLIB.ORG

Entangled Dynamos and Joule Heating in the Earth's Ionosphere

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Entangled Dynamos and Joule Heating in the Earth's Ionosphere Ann. Geophys., 38, 1019–1030, 2020 https://doi.org/10.5194/angeo-38-1019-2020 © Author(s) 2020. This work is distributed under the Creative Commons Attribution 4.0 License. Entangled dynamos and Joule heating in the Earth’s ionosphere Stephan C. Buchert Swedish Institute of Space Physics, Uppsala, Sweden Correspondence: Stephan C. Buchert ([email protected]) Received: 9 May 2019 – Discussion started: 21 May 2019 Revised: 2 June 2020 – Accepted: 5 August 2020 – Published: 24 September 2020 Abstract. The Earth’s neutral atmosphere is the driver of the cently by Yamazaki and Maute(2017). Sq is driven by a well-known solar quiet (Sq) and other magnetic variations neutral dynamo. Vasyliunas¯ (2012) has summarized the fun- observed for more than 100 years. Yet the understanding of damental equations for a neutral dynamo and his critical view how the neutral wind can accomplish a dynamo effect has of the understanding within the community. The conceptual been incomplete. A new viable model is presented where a difficulty of the author’s interpretation of the neutral dynamo dynamo effect is obtained only in the case of winds perpen- can be phrased less mathematically as follows: in the frame dicular to the magnetic field B that do not map along B. of the neutral gas the product j · E∗, j the electric current, Winds where u × B is constant have no effect. We identify and E∗ the electric field is in the steady state zero or pos- Sq as being driven by wind differences at magnetically con- itive, because of the well-known Ohm’s law for the iono- jugate points and not by a neutral wind per se. The view of sphere. This indicates that Joule heating takes place (which, two different but entangled dynamos is favoured, with some however, has not been addressed yet in works specifically on conceptual analogy to quantum mechanical states. Because Sq, as far as we are aware of). A common comprehension of the large preponderance of the neutral gas mass over the seems to be that the dynamo effect occurs in the Earth-fixed ionized component in the Earth’s ionosphere, the dominant frame where j · E∗ − u × B, u the neutral wind, can be effect of the plasma adjusting to the winds is Joule heating. negative as required for a dynamo. However, a clear justifi- The amount of global Joule heating power from Sq is esti- cation for choosing this Earth-fixed frame over any other of mated, with uncertainties, to be much lower than Joule heat- the infinitely many possible frames, for example, Sun-fixed ing from ionosphere–magnetosphere coupling at high lati- or star-fixed inertial frames, seems to be lacking. Undoubt- tudes in periods of strong geomagnetic activity. However, on edly Sq variations have to do with neutral motion, but a neu- average both contributions could be relatively comparable. tral wind u and associated motional field u × B are frame The global contribution of heating by ionizing solar radiation dependent. In the frame of the neutral gas both are zero. So in the same height range should be 2–3 orders of magnitude what exactly drives the Sq currents and fields? larger. We will first present a new viable steady-state model of the neutral dynamo in the Earth’s ionosphere. As the title suggests, it actually involves (at least) two dynamos. A dis- cussion of various aspects of the new model follows, with 1 Introduction further references to other works on the subject. The interaction between the ionospheric plasma and neutral wind in the Earth’s atmosphere has been described in schol- 2 Preliminaries arly textbooks (e.g. Kelley, 2009) and numerous research ar- ticles. Still, for a long time the author has felt that his un- A scenario is considered where the lower thermosphere derstanding of the subject is incomplete. In this work we within two circles of latitude in each hemisphere is connected describe progress that has been finally made when thinking by the dipolar geomagnetic field, as sketched in Fig.1. In about the solar quiet (Sq) magnetic variations at mid lati- the Northern Hemisphere branch an easterly (westerly) zonal tudes. A praiseworthy review of Sq has been published re- wind flows, with a westerly (easterly) wind in the Southern Published by Copernicus Publications on behalf of the European Geosciences Union. 1020 S. C. Buchert: Entangled dynamos and Joule heating practically instantaneously, with only small amplitudes in the transients. We use the jargon and paradigms of the iono- sphere community. Astrophysical dynamos (usually without a neutral gas) are typically rather described in terms of a mechanical magnetohydrodynamics (MHD) approach. Dif- ferences between the two approaches have been discussed by Parker(1996) for the high latitudes and by Vasyli unas¯ (2012) for specifically the Earth’s neutral wind dynamo. Both authors acknowledged that for the steady state both ap- proaches give equivalent results and that for highly symmet- ric cases, such as this one, the “traditional” ionospheric E and j paradigm is efficient and mathematically simpler. The electrodynamics of the ionosphere particularly in the steady state and with a neutral gas is treated in a scholarly manner by Kelley(2009). For completeness we rephrase the most important points relevant for this work: in the reference frame of the neutral gas in the dynamo region, roughly at altitudes 90–200 km, where collisions are significant, an electric field E∗ drives Pedersen and Hall currents J P and J H according to Ohm’s law for the ionosphere: ∗ ∗ J P D 6PE ; J H D −6HE × B=B: (1) Figure 1. 3-D sketch of a scenario where regions between L D 2:5 6P and 6H are the Pedersen and Hall conductances and B and 3 are magnetically connected by a dipole magnetic field. The the magnetic field. The electric field E in other reference Supplement includes this figure in html format which, when opened frames with the neutral gas velocity u 6D 0 is in a browser supporting JavaScript, allows one to change the camera ∗ view point. E D E − u × B: (2) Please note that in many publications this equation is written with the Cu × B term on the E side, which is the standard Hemisphere. A zero tilt between geodetic directions (west- form of the Lorentz transformation for non-relativistic veloc- erly, easterly) and magnetic field-aligned Cartesian coordi- ities u. Often E is measured in some frame (for example the nates is assumed. An ionosphere with a dynamo region ex- Earth-fixed one), and the task is to estimate E∗. In this work ists, as well as magnetized plasma in a plasmasphere (not we prefer to write the relation as in Eq. (2). It is here im- sketched in Fig.1). The plasma adjusts to the conditions portant to note that E∗ is a frame-independent field driving imposed by the neutral winds but does not interfere oth- currents according to Eq. (1). The frame-dependent motional erwise, meaning that neither plasma pressure gradients nor u × B does not drive any currents; it is not a real field. electric fields penetrating from outside, etc., play any role. In the topside ionosphere and plasmasphere collisions are Zero meridional wind is assumed, and the deviation of the rare and the plasma drifts such that E C v × B D 0, and v is magnetic field B from a vertical inclination in the latitude the ion or electron drift. This means that the electric field in range of the zonal wind is ignored. The latitude range is the frame of the plasma is zero. The conductivity along B small, such that gradients of u, B, and the height-integrated is very high compared to the Pedersen and Hall conductivi- Pedersen conductivity 6P across the range are neglected. In ties, and in the steady state Ek D 0. For constant B, E .z/ is other words, u, B, and 6P are assumed constant across the also constant (where z is the coordinate along B). This justi- latitudes of the zonal jets. u and B are also assumed constant fies using height-integrated quantities in Eq. (1). When com- over the altitude range where there is significant collisional paring electric fields between the magnetosphere and iono- interaction with the plasma. In other words, the ionosphere sphere, B is not constant and E is said to “map” between is assumed to be thin. The scenario is highly simplified com- positions along z (Kelley, 2009, Chapter 2.4). For the sce- pared to any realistic one, in order to achieve a good physical nario in Fig.1 we also require such mapping of E between understanding of the situation. hemispheres. Owing to the highly symmetric preconditions We strive only for a steady-state description. The neutral the mapping is simply that a northward E in the Northern wind in the Earth’s ionosphere at mid latitudes changes only Hemisphere maps to southward in the Southern Hemisphere slowly over timescales of several hours, and the plasma be- with equal magnitudes and analogously for reversed direc- tween hemispheres would be able to adjust within seconds, tions of E. Ann. Geophys., 38, 1019–1030, 2020 https://doi.org/10.5194/angeo-38-1019-2020 S. C. Buchert: Entangled dynamos and Joule heating 1021 ∗ × · ∗ The Pedersen current driven by E is associated with Joule EN 1B/µ0 matching the Joule heating JN EN in the N or frictional heating (Vasyliunas¯ and Song, 2005) with power dynamo. −2 ∗ DQ ∗ ∗ in Wm : In SES uB is also northward; i.e. EN and ES do not map to each other along the magnetic field.
Load more

Recommended publications
  • 3-D Electromagnetic Radiative Non-Newtonian Nanofluid Flow With
    www.nature.com/scientificreports OPEN 3‑D electromagnetic radiative non‑Newtonian nanofuid fow with Joule heating and higher‑order reactions in porous materials Amel A. Alaidrous1* & Mohamed R. Eid2,3* The aim of this work is to discuss the efect of mth‑order reactions on the magnetic fow of hyperbolic tangent nanofuid through extending surface in a porous material with thermal radiation, several slips, Joule heating, and viscous dissipation. In order to convert non‑linear partial diferential governing equations into ordinary ones, a technique of similarity transformations has been implemented and then solved using the OHAM (optimal homotopy analytical method). The outcomes of novel efective parameters on the non‑dimensional interesting physical quantities are established utilizing the tabular and pictorial outlines. After a comparison with previous literature studies, the results were fnely compliant. The study explores that the reduced Nusselt number is diminished for the escalating values of radiation, porosity, and source (sink) parameters. It is found that the order of the chemical reaction m = 2 is dominant in concentration as well as mass transfer in both destructive and generative reactions. When m reinforces for a destructive reaction, mass transfer is reduced with 34.7% and is stabled after η = 3. In the being of the destructive reaction and Joule heating, the nanofuid’s temperature is enhanced. Abbreviations a, b Constants (–) B0 Magnetic parameter C Concentration (mol/m3) cp Specifc heat C Free stream concentration (mol/m3)
    [Show full text]
  • Electric Permittivity of Carbon Fiber
    Carbon 143 (2019) 475e480 Contents lists available at ScienceDirect Carbon journal homepage: www.elsevier.com/locate/carbon Electric permittivity of carbon fiber * Asma A. Eddib, D.D.L. Chung Composite Materials Research Laboratory, Department of Mechanical and Aerospace Engineering, University at Buffalo, The State University of New York, Buffalo, NY, 14260-4400, USA article info abstract Article history: The electric permittivity is a fundamental material property that affects electrical, electromagnetic and Received 19 July 2018 electrochemical applications. This work provides the first determination of the permittivity of contin- Received in revised form uous carbon fibers. The measurement is conducted along the fiber axis by capacitance measurement at 25 October 2018 2 kHz using an LCR meter, with a dielectric film between specimen and electrode (necessary because an Accepted 11 November 2018 LCR meter is not designed to measure the capacitance of an electrical conductor), and with decoupling of Available online 19 November 2018 the contributions of the specimen volume and specimen-electrode interface to the measured capaci- tance. The relative permittivity is 4960 ± 662 and 3960 ± 450 for Thornel P-100 (more graphitic) and Thornel P-25 fibers (less graphitic), respectively. These values are high compared to those of discon- tinuous carbons, such as reduced graphite oxide (relative permittivity 1130), but are low compared to those of steels, which are more conductive than carbon fibers. The high permittivity of carbon fibers compared to discontinuous carbons is attributed to the continuity of the fibers and the consequent substantial distance that the electrons can move during polarization. The P-100/P-25 permittivity ratio is 1.3, whereas the P-100/P-25 conductivity ratio is 67.
    [Show full text]
  • Joule Heating of the South Polar Terrain on Enceladus K
    JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 116, E04010, doi:10.1029/2010JE003776, 2011 Joule heating of the south polar terrain on Enceladus K. P. Hand,1 K. K. Khurana,2 and C. F. Chyba3 Received 12 November 2010; revised 1 February 2011; accepted 13 February 2011; published 27 April 2011. [1] We report that Joule heating in Enceladus, resulting from the interaction of Enceladus with Saturn’s magnetic field, may account for 150 kW to 52 MW of power through Enceladus. Electric currents passing through subsurface channels of low salinity and just a few kilometers in depth could supply a source of power to the south polar terrain, providing a small but previously unaccounted for contribution to the observed heat flux and plume activity. Studies of the electrical heating of Jupiter’s moon Europa have concluded that electricity is a negligible heating source since no connection between the conductive subsurface and Alfvén currents has been observed. Here we show that, contrary to results for the Jupiter system, electrical heating may be a source of internal energy for Enceladus, contributing to localized heating, production of water vapor, and the persistence of the “tiger stripes.” This contribution is of order 0.001–0.25% of the total observed heat flux, and thus, Joule heating cannot explain the total south polar terrain heat anomaly. The exclusion of salt ions during refreezing serves to enhance volumetric Joule heating and could extend the lifetime of liquid water fractures in the south polar terrain. Citation: Hand, K. P., K. K. Khurana, and C. F. Chyba (2011), Joule heating of the south polar terrain on Enceladus, J.
    [Show full text]
  • Joule Heating-Induced Particle Manipulation on a Microfluidic Chip
    Joule Heating-Induced Particle Manipulation on a Microfluidic Chip Golak Kunti,a) Jayabrata Dhar,b) Anandaroop Bhattacharyaa) and Suman Chakrabortya)* a)Department of Mechanical Engineering, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal - 721302, India b)Universite de Rennes 1, CNRS, Geosciences Rennes UMR6118, Rennes, France *E-mail address of corresponding author: [email protected] We develop an electrokinetic technique that continuously manipulates colloidal particles to concentrate into patterned particulate groups in an energy efficient way, by exclusive harnessing of the intrinsic Joule heating effects. Our technique exploits the alternating current electrothermal flow phenomenon which is generated due to the interaction between non-uniform electric and thermal fields. Highly non-uniform electric field generates sharp temperature gradients by generating spatially-varying Joule heat that varies along radial direction from a concentrated point hotspot. Sharp temperature gradients induce local variation in electric properties which, in turn, generate strong electrothermal vortex. The imposed fluid flow brings the colloidal particles at the centre of the hotspot and enables particle aggregation. Further, manoeuvering structures of the Joule heating spots, different patterns of particle clustering may be formed in a low power budget, thus, opening up a new realm of on-chip particle manipulation process without necessitating highly focused laser beam which is much complicated and demands higher power budget. This technique can find its use in Lab-on-a-chip devices to manipulate particle groups, including biological cells. INTRODUCTION Manipulation and assembly of colloidal particles including biological cells are essential in colloidal crystals, biological assays, bioengineered tissues, and engineered Laboratory-on- a-chip (LOC) devices.1–6 Concentrating, sorting, patterning and transporting of microparticles possess several challenges in these devices/systems.
    [Show full text]
  • Lecture 1: Basic Terms and Rules in Mathematics
    Lecture 5: electricity Content: - introduction - electric charge, potential, field, current, flux - electric dipole - resistance, conductance, Ohm‘s law - resistivity, conductivity - Kirchhoff's circuit laws - dielectric materials, permittivity - capacitor, capacitance - alternating current - skin effect, dispersion - Gaussian law in electrics fundamentals of electric field Electricity is the set of physical phenomena associated with the presence and flow of electric charge. Electric charge has a positive and negative sign. Electricity gives a wide variety of well-known effects, such as lightning, static electricity, electromagnetic induction and electric current (naturally originated). In addition, electricity permits the creation and reception of electromagnetic radiation such as radio waves. fundamentals of electric field Charge carriers: - in metals, the charge carriers are electrons (they are able to move about freely within the crystal structure of the metal). (a cloud of free electrons is called as a Fermi gas). - in electrolytes (such as salt water) the charge carriers are ions, atoms or molecules that have gained or lost electrons so they are electrically charged (anions, cations). This is valid also in melted ionic solids. - in a plasma, an electrically charged gas which is found in electric arcs through air, the electrons and cations of ionized gas act as charge carriers. - in a vacuum, free electrons can act as charge carriers. - in semiconductors (used in electronics), in addition to electrons, the travelling vacancies in the valence-band electron population (called "holes"), act as mobile positive charges and are treated as charge carriers. interesting trials with plasma lamp: https://www.youtube.com/watch?v=2gttW4F86Sg fundamentals of electric field Basic quantities: - electric charge: a property of some subatomic particles, which determines their electromagnetic interactions.
    [Show full text]
  • The Effects of Joule Heating on Electric-Driven Microfluidic Flow Alexander P
    Research Article from the SC Junior Academy of Science The Effects of Joule Heating on Electric-Driven Microfluidic Flow Alexander P. Spitzer South Carolina Governor’s School for Science and Mathematics This study sought out to more clearly understand the relationship between Joule heating and fluid flow in microfluidic environments, and more specifically, under what circumstances would the fluid flow in the device possibly hinder an experiment being run on it. It had been previous theorised that an electric field may produce turbulence and even vortices within the fluid, which this study attempted to reproduce. Several variables were tested, namely insulating and conducting fluids, higher and lower AC voltages, Newtonian vs. non- Newtonian fluids, and higher and lower DC voltages. A correlation between these variables and turbulent flow was found, with more conductive fluids, higher AC voltages, non-Newtonian fluids, and higher DC voltages more prone to fluid turbulence. Introduction Lab-on-a-chip devices are widely used in research to perform microfluidic chemical and biomedical analysis. However, some of these chips are driven using an electric field, which can cause potentially catastrophic side-effects, one of which is joule heating. Joule heating is an effect where heat is produced in a medium through which an electric current is passed. This can be an issue in microfluidic devices, especially in those with designs that contain constrictions in their channels. Due to the fact that electrical resistance increases with decreasing cross-sectional area and more heat is produce when resistance increases, temperature gradients can form in the fluid. This creates chaotic flow that may disrupt any experiment being performed on the chip.
    [Show full text]
  • Joule Heating in Nanowires
    Accepted for publication in Physical Review B (6 May 2011) Joule heating in nanowires Hans Fangohr,1, ∗ Dmitri S. Chernyshenko,1 Matteo Franchin,1 Thomas Fischbacher,1 and Guido Meier2 1School of Engineering Sciences, University of Southampton, SO17 1BJ, Southampton, United Kingdom 2Institut f¨urAngewandte Physik und Zentrum f¨urMikrostrukturforschung, Universit¨atHamburg, Jungiusstrasse 11, 20355 Hamburg, Germany We study the effect of Joule heating from electric currents flowing through ferromagnetic nanowires on the temperature of the nanowires and on the temperature of the substrate on which the nanowires are grown. The spatial current density distribution, the associated heat generation, and diffusion of heat is simulated within the nanowire and the substrate. We study several different nanowire and constriction geometries as well as different substrates: (thin) silicon nitride membranes, (thick) silicon wafers, and (thick) diamond wafers. The spatially resolved increase in temperature as a function of time is computed. For effectively three-dimensional substrates (where the substrate thickness greatly exceeds the nanowire length), we identify three different regimes of heat propagation through the substrate: regime (i), where the nanowire temperature increases approximately logarithmically as a function of time. In this regime, the nanowire temperature is well-described analytically by You et al. [APL89, 222513 (2006)]. We provide an analytical expression for the time tc that marks the upper applicability limit of the You model. After tc, the heat flow enters regime (ii), where the nanowire temperature stays constant while a hemispherical heat front carries the heat away from the wire and into the substrate. As the heat front reaches the boundary of the substrate, regime (iii) is entered where the nanowire and substrate temperature start to increase rapidly.
    [Show full text]
  • Experimental Evidence in Support of Joule Heating Associated with Geomagnetic Activity
    SA TECHNICAL NOTE LOAN COPY AFWL ( KIRTLAND EXPERIMENTAL EVIDENCE IN SUPPORT OF JOULE HEATING ASSOCIATED WITH GEOMAGNETIC ACTIVITY b by Leonard L. DeVries George C. Marshall Spuce Flight Center Marshall Space Flight Center, Ala 35812 NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON, D. C. NOVEMBER 1971 I TECH LIBRARY KAFB, NM 1. Report No. 2. Government Accession No. .LLKL.. I I 4. Title and Subtitle 1 5. Report Date I November 1971 Experimental Evidence in Support of Joule Heating 6. Performing Organization Code Associated with Geomagnetic Activity I I 7. Author(s) I El. Performing Organization Report No. MI75 Leonard L. DeVries I 10. Work.Unit No. I 9. Performing Organization Name and Address I 976-30-00 George C. Marshall Space Flight Center 11. Contract or Grant No. Marshall Space Flight Center, Alabama 35812 13. Type of Report and Period Covered 12. Sponsoring Agency Name and Address National Aeronautics and Space Administration Washington, D.C. 20546 15. Supplementary Notes Prepared by Aero-Astrodynamics Laboratory, Science and Engineering I 16. Abstract High resolution acccleromctcr measurements in the altitude region 140 to 300 km from a satellite in a near-polar orbit during a period of extremely high geomagnetic activity indicate that Joule heating is tlie primary source of energy for atmospheric heating associated with geomagnetic activity. This concl~isionis supported by the following observational evidence: (I) There is an atmospheric rcsponsc in tlie auroral zone which is nearly simultaneous with the onset of geomagnetic activity, with no significant response in the equatorial region until several hours later; (2) the maximum heating occurs at geographic locations near the maximum current of the auroral electrojet; and (3) there is evidence of atmospheric waves originating near the auroral zone at altitudes where Joule heating would be expected to occur.
    [Show full text]
  • Preview of Period 13: Electrical Resistance and Joule Heating
    Preview of Period 13: Electrical Resistance and Joule Heating 13.1 Electrical Resistance of a Wire What does the resistance of a wire depend upon? 13.2 Resistance and Joule Heating What effect does resistance have on current flow? What is joule heating? 13.3 Temperature and Resistance How does the temperature of a wire affect its resistance? 13-1 Measuring Resistance with a Multimeter 1. Turn the dial to the ohm symbol (Ω). 2. Check that the wire leads are attached to the outlets on the lower right of the meter. 3. To measure resistance, touch the ends of the leads to each end of the resistor wire. Ω V Ω COM 13-2 Act. 13.1: Measuring Resistance Measuring the resistance of the 30 cm wire. Ω 1. Do not connect the battery tray to the green board with resistance wires. 2. Set the multimeter to “ Ω ” to measure resistance. 3. Touch the ends of the multimeter leads across the thin 30 cm wire to measure its resistance. Then move the multimeter leads to the ends of the 15 cm wire to measure its resistance. 13-3 Act.13.1: Resistance of a Wire Resistance of a wire = Resistivity x Length Area ρ L R = A R = resistance (in ohms) ρ = resistivity (in ohm meters) L = length of resistor (in meters) A = cross-sectional area (in meters2) A Wire Resistor of Length L and Cross-Sectional Area A A L 13-4 Joule Heating in Wires ♦ Current flowing through wires encounters resistance, and some electrical energy is transformed into thermal energy.
    [Show full text]
  • Chapter 20: Electric Current, Resistance & Ohm's
    Chapter 20: Electric Current, Resistance & Ohm’s Law Brent Royuk Phys-112 Concordia University The “Minds of Our Own” Challenge • Light a bulb with a battery and a wire. Could you do it? 2 Introduction • Batteries supply charge to produce a current – How? Electrochemistry stuff: oxy/redux • cathode and anode • dry cell vs. battery – Electric current = moving charges • dc vs. ac • How does this relate to electrostatics? – Electroscope and D-cell? – Voltage of charge strips 3 Electric Current • Current Flow – Consider a simple circuit diagram • What direction does the current flow? – Electron flow vs. conventional current • Curse you Ben Franklin! 4 Electric Current ΔQ • Definition: I = Δt • Unit: The ampere (A) – “amps” • 1 A =€ 6.25 x 1018 electrons/s 5 The Water Pump Analogy 6 Drift Velocity • Even without a potential, electrons are in constant motion • Electric field --> force --> drift velocity – How many conduction electrons are in a wire? • So drift velocities are often very slow, like walking speeds. • So why don’t we have to wait for the light when we hit the switch? – What moves fast? – “Marbles in a tube” analogy 7 Ohm’s Law • Two laws for resistive circuits: – I α ΔV – I α 1/R • Put them together and you get V = IR – Ohm’s Law 8 Ohm’s Law • Definition of resistance: R = V/I – Resistance Unit: The ohm (Ω) • Ohm’s Law doesn’t apply to all materials – E.g. semi-conductors, lightbulb filaments – (Known as Ohmic & Non-Ohmic materials) 9 Resistivity • Resistivity is a measure of how well a material conducts electricity.
    [Show full text]
  • Joule's Experiment: an Historico-Critical Approach
    Joule's experiment: An historico-critical approach Author: Marcos Pou Gallo Advisor: Enric P´erezCanals Facultat de F´ısica, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain. Abstract: We present the result of the historical analysis of Joule's paper \The mechanical equivalent of heat" (1849). We give a brief but close examination of his measurements of the mechanical value of a calorie, as well as their influence in the birth of thermodynamics. I. INTRODUCTION know it today wasn't even born. Heat, temperature and energy belong to different The study of heat and temperature yielded a great scales, such as the motion of microscopic particles and number of contradictions to resolve. Concepts like the thermal state a certain body. In the 19th century \heat" or \temperature" were confused and usually these concepts were widely discussed. The discoveries misunderstood. In the eighteenth century these ideas and the experiments of those years changed physics had been widely discussed, but we want to emphasize and its way of explaining reality. Among the involved the work by Joseph Black. The fact that heat had a scientists, James Prescott Joule stands out with his kind of capacity to increment an object's temperature famous measurement of the mechanical equivalent of by contact made him think that fire (for instance) had heat. \something" that passed to other objects [3]. Other experiments suggested to Black that heat was not Joule's experiment had a big influence and was one created or destroyed; it simply changed \location". The of the most relevant results around the emergence of temperature that a body gain when heated would be the principle of conservation of energy.
    [Show full text]
  • Electric & Induction Heating
    Electric & Induction Heating Introduction: Electric heating is any process in which electrical energy is converted to heat. Common applications include heating of buildings, cooking, and industrial processes .An electric heater is an electrical appliance that converts electrical energy into heat. The heating element inside every electric heater is simply an electrical resistor, and works on the principle of Joule heating: an electric current through a resistor converts electrical energy into heat energy.Alternatively, a heat pump uses an electric motor to drive a refrigeration cycle, drawing heat from a source such as the ground or outside air and directing it into the space to be warmed. Definition Dielectric heating (also known as electronic heating, RF heating, high-frequency heating) is the process in which radiowave or microwave electromagnetic radiation heats a dielectric material. This heating is caused by dipole rotation. Power For dielectric heating the generated power density per volume is calculated by Induction heating Induction heating is the process of heating an electrically conducting object (usually a metal) by electromagnetic induction, where eddy currents are generated within the metal and resistance leads to Joule heating of the metal. An induction heater (for any process) consists of an electromagnet, through which a high-frequency alternating current (AC) is passed. Heat may also be generated by magnetic hysteresis losses in materials that have significant relative permeability. The frequency of AC used depends on
    [Show full text]