Chapter 3 Electromagnetic Fields
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Gauss's Law II
Gauss’s law II If a lightning bolt strikes a car (unless it is a convertible), electrons would quickly (in the order of nano seconds) move to the surface, so it is almost an ideal conductive shell that you can hide inside during a lightning storm! Reading: Mazur 24.7-25.2 Deriving Gauss’s law Applying Gauss’s law Electric potential energy Electrostatic work LECTURE 7 1 24.7 Deriving Gauss’s law Gauss’s law states that the flux through a closed surface is proportional to the enclosed charge, �"#$, such that �"#$ Φ& = �) LECTURE 7 2 Question: 24.7-1 (Flux from point charge) Consider a spherical Gaussian surface of radius � with a point charge � at the center. � 1 ⃗ The flux through a surface is given by Φ& = ∮1 � ⋅ ��. Using this definition for flux and Coulomb's law, calculate the flux through the Gaussian surface in terms of �, �, � and any constants. LECTURE 7 3 Question: 24.7-1 (Flux from point charge) answer Consider a spherical Gaussian surface of radius � with a point charge � at the center. � 1 ⃗ The flux through a surface is given by Φ& = ∮1 � ⋅ ��. Using this definition for flux and Coulomb's law, calculate the flux through the Gaussian surface in terms of �, �, � and any constants. The electric field is always normal to the Gaussian surface and has equal magnitude at all points on the surface. Therefore 1 1 1 � Φ = 3 � ⋅ ��⃗ = 3 ��� = � 3 �� = � 4��6 = � 4��6 = 4��� & �6 1 1 1 7 From Gauss’s law Φ& = 89 7 : Therefore Φ& = = 4���, and �) = 89 ;<= LECTURE 7 4 Reading quiz (Problem 24.70) There is a Gauss's law for gravity analogous to Gauss's law for electricity. -
An Atomic Physics Perspective on the New Kilogram Defined by Planck's Constant
An atomic physics perspective on the new kilogram defined by Planck’s constant (Wolfgang Ketterle and Alan O. Jamison, MIT) (Manuscript submitted to Physics Today) On May 20, the kilogram will no longer be defined by the artefact in Paris, but through the definition1 of Planck’s constant h=6.626 070 15*10-34 kg m2/s. This is the result of advances in metrology: The best two measurements of h, the Watt balance and the silicon spheres, have now reached an accuracy similar to the mass drift of the ur-kilogram in Paris over 130 years. At this point, the General Conference on Weights and Measures decided to use the precisely measured numerical value of h as the definition of h, which then defines the unit of the kilogram. But how can we now explain in simple terms what exactly one kilogram is? How do fixed numerical values of h, the speed of light c and the Cs hyperfine frequency νCs define the kilogram? In this article we give a simple conceptual picture of the new kilogram and relate it to the practical realizations of the kilogram. A similar change occurred in 1983 for the definition of the meter when the speed of light was defined to be 299 792 458 m/s. Since the second was the time required for 9 192 631 770 oscillations of hyperfine radiation from a cesium atom, defining the speed of light defined the meter as the distance travelled by light in 1/9192631770 of a second, or equivalently, as 9192631770/299792458 times the wavelength of the cesium hyperfine radiation. -
Maxwell's Equations
Maxwell’s Equations Matt Hansen May 20, 2004 1 Contents 1 Introduction 3 2 The basics 3 2.1 Static charges . 3 2.2 Moving charges . 4 2.3 Magnetism . 4 2.4 Vector operations . 5 2.5 Calculus . 6 2.6 Flux . 6 3 History 7 4 Maxwell’s Equations 8 4.1 Maxwell’s Equations . 8 4.2 Gauss’ law for electricity . 8 4.3 Gauss’ law for magnetism . 10 4.4 Faraday’s law . 11 4.5 Ampere-Maxwell law . 13 5 Conclusion 14 2 1 Introduction If asked, most people outside a physics department would not be able to identify Maxwell’s equations, nor would they be able to state that they dealt with electricity and magnetism. However, Maxwell’s equations have many very important implications in the life of a modern person, so much so that people use devices that function off the principles in Maxwell’s equations every day without even knowing it. 2 The basics 2.1 Static charges In order to understand Maxwell’s equations, it is necessary to understand some basic things about electricity and magnetism first. Static electricity is easy to understand, in that it is just a charge which, as its name implies, does not move until it is given the chance to “escape” to the ground. Amounts of charge are measured in coulombs, abbreviated C. 1C is an extraordi- nary amount of charge, chosen rather arbitrarily to be the charge carried by 6.41418 · 1018 electrons. The symbol for charge in equations is q, sometimes with a subscript like q1 or qenc. -
Chapter 16 – Electrostatics-I
Chapter 16 Electrostatics I Electrostatics – NOT Really Electrodynamics Electric Charge – Some history •Historically people knew of electrostatic effects •Hair attracted to amber rubbed on clothes •People could generate “sparks” •Recorded in ancient Greek history •600 BC Thales of Miletus notes effects •1600 AD - William Gilbert coins Latin term electricus from Greek ηλεκτρον (elektron) – Greek term for Amber •1660 Otto von Guericke – builds electrostatic generator •1675 Robert Boyle – show charge effects work in vacuum •1729 Stephen Gray – discusses insulators and conductors •1730 C. F. du Fay – proposes two types of charges – can cancel •Glass rubbed with silk – glass charged with “vitreous electricity” •Amber rubbed with fur – Amber charged with “resinous electricity” A little more history • 1750 Ben Franklin proposes “vitreous” and “resinous” electricity are the same ‘electricity fluid” under different “pressures” • He labels them “positive” and “negative” electricity • Proposaes “conservation of charge” • June 15 1752(?) Franklin flies kite and “collects” electricity • 1839 Michael Faraday proposes “electricity” is all from two opposite types of “charges” • We call “positive” the charge left on glass rubbed with silk • Today we would say ‘electrons” are rubbed off the glass Torsion Balance • Charles-Augustin de Coulomb - 1777 Used to measure force from electric charges and to measure force from gravity = - - “Hooks law” for fibers (recall F = -kx for springs) General Equation with damping - angle I – moment of inertia C – damping -
Units and Magnitudes (Lecture Notes)
physics 8.701 topic 2 Frank Wilczek Units and Magnitudes (lecture notes) This lecture has two parts. The first part is mainly a practical guide to the measurement units that dominate the particle physics literature, and culture. The second part is a quasi-philosophical discussion of deep issues around unit systems, including a comparison of atomic, particle ("strong") and Planck units. For a more extended, profound treatment of the second part issues, see arxiv.org/pdf/0708.4361v1.pdf . Because special relativity and quantum mechanics permeate modern particle physics, it is useful to employ units so that c = ħ = 1. In other words, we report velocities as multiples the speed of light c, and actions (or equivalently angular momenta) as multiples of the rationalized Planck's constant ħ, which is the original Planck constant h divided by 2π. 27 August 2013 physics 8.701 topic 2 Frank Wilczek In classical physics one usually keeps separate units for mass, length and time. I invite you to think about why! (I'll give you my take on it later.) To bring out the "dimensional" features of particle physics units without excess baggage, it is helpful to keep track of powers of mass M, length L, and time T without regard to magnitudes, in the form When these are both set equal to 1, the M, L, T system collapses to just one independent dimension. So we can - and usually do - consider everything as having the units of some power of mass. Thus for energy we have while for momentum 27 August 2013 physics 8.701 topic 2 Frank Wilczek and for length so that energy and momentum have the units of mass, while length has the units of inverse mass. -
Estimation of Forest Aboveground Biomass and Uncertainties By
Urbazaev et al. Carbon Balance Manage (2018) 13:5 https://doi.org/10.1186/s13021-018-0093-5 RESEARCH Open Access Estimation of forest aboveground biomass and uncertainties by integration of feld measurements, airborne LiDAR, and SAR and optical satellite data in Mexico Mikhail Urbazaev1,2* , Christian Thiel1, Felix Cremer1, Ralph Dubayah3, Mirco Migliavacca4, Markus Reichstein4 and Christiane Schmullius1 Abstract Background: Information on the spatial distribution of aboveground biomass (AGB) over large areas is needed for understanding and managing processes involved in the carbon cycle and supporting international policies for climate change mitigation and adaption. Furthermore, these products provide important baseline data for the development of sustainable management strategies to local stakeholders. The use of remote sensing data can provide spatially explicit information of AGB from local to global scales. In this study, we mapped national Mexican forest AGB using satellite remote sensing data and a machine learning approach. We modelled AGB using two scenarios: (1) extensive national forest inventory (NFI), and (2) airborne Light Detection and Ranging (LiDAR) as reference data. Finally, we propagated uncertainties from feld measurements to LiDAR-derived AGB and to the national wall-to-wall forest AGB map. Results: The estimated AGB maps (NFI- and LiDAR-calibrated) showed similar goodness-of-ft statistics (R 2, Root Mean Square Error (RMSE)) at three diferent scales compared to the independent validation data set. We observed diferent spatial patterns of AGB in tropical dense forests, where no or limited number of NFI data were available, with higher AGB values in the LiDAR-calibrated map. We estimated much higher uncertainties in the AGB maps based on two-stage up-scaling method (i.e., from feld measurements to LiDAR and from LiDAR-based estimates to satel- lite imagery) compared to the traditional feld to satellite up-scaling. -
6.007 Lecture 5: Electrostatics (Gauss's Law and Boundary
Electrostatics (Free Space With Charges & Conductors) Reading - Shen and Kong – Ch. 9 Outline Maxwell’s Equations (In Free Space) Gauss’ Law & Faraday’s Law Applications of Gauss’ Law Electrostatic Boundary Conditions Electrostatic Energy Storage 1 Maxwell’s Equations (in Free Space with Electric Charges present) DIFFERENTIAL FORM INTEGRAL FORM E-Gauss: Faraday: H-Gauss: Ampere: Static arise when , and Maxwell’s Equations split into decoupled electrostatic and magnetostatic eqns. Electro-quasistatic and magneto-quasitatic systems arise when one (but not both) time derivative becomes important. Note that the Differential and Integral forms of Maxwell’s Equations are related through ’ ’ Stoke s Theorem and2 Gauss Theorem Charges and Currents Charge conservation and KCL for ideal nodes There can be a nonzero charge density in the absence of a current density . There can be a nonzero current density in the absence of a charge density . 3 Gauss’ Law Flux of through closed surface S = net charge inside V 4 Point Charge Example Apply Gauss’ Law in integral form making use of symmetry to find • Assume that the image charge is uniformly distributed at . Why is this important ? • Symmetry 5 Gauss’ Law Tells Us … … the electric charge can reside only on the surface of the conductor. [If charge was present inside a conductor, we can draw a Gaussian surface around that charge and the electric field in vicinity of that charge would be non-zero ! A non-zero field implies current flow through the conductor, which will transport the charge to the surface.] … there is no charge at all on the inner surface of a hollow conductor. -
Symmetry • the Concept of Flux • Calculating Electric Flux • Gauss's
Topics: • Symmetry • The Concept of Flux • Calculating Electric Flux • Gauss’s Law • Using Gauss’s Law • Conductors in Electrostatic Equilibrium PHYS 1022: Chap. 28, Pg 2 1 New Topic PHYS 1022: Chap. 28, Pg 3 For uniform field, if E and A are perpendicular, define If E and A are NOT perpendicular, define scalar product General (surface integral) Unit of electric flux: N . m2 / C Electric flux is proportional to the number of field lines passing through the area. And to the total change enclosed PHYS 1022: Chap. 28, Pg 4 2 + + PHYS 1022: Chap. 28, Pg 5 + + PHYS 1022: Chap. 28, Pg 6 3 r + ½r + 2r PHYS 1022: Chap. 28, Pg 7 r + ½r + 2r PHYS 1022: Chap. 28, Pg 8 4 A metal block carries a net positive charge and put in an electric field. 1) 0 What is the electric field inside? 2) positive 3) Negative 4) Cannot be determined If there is an electric field inside the conductor, it will move the charges in the conductor to where each charge is in equilibrium. That is, net force = 0 therefore net field = 0! PHYS 1022: Chap. 28, Pg 9 A metal block carries a net charge and 1) All inside the conductor put in an electric field. Where does 2) All on the surface the net charge reside ? 3) Some inside the conductor, some on the surface The net field = 0 inside, and so the net flux through any surface drawn inside the conductor = 0. Therefore the net charge inside = 0! PHYS 1022: Chap. 28, Pg 10 5 PHYS 1022: Chap. -
Improving the Accuracy of the Numerical Values of the Estimates Some Fundamental Physical Constants
Improving the accuracy of the numerical values of the estimates some fundamental physical constants. Valery Timkov, Serg Timkov, Vladimir Zhukov, Konstantin Afanasiev To cite this version: Valery Timkov, Serg Timkov, Vladimir Zhukov, Konstantin Afanasiev. Improving the accuracy of the numerical values of the estimates some fundamental physical constants.. Digital Technologies, Odessa National Academy of Telecommunications, 2019, 25, pp.23 - 39. hal-02117148 HAL Id: hal-02117148 https://hal.archives-ouvertes.fr/hal-02117148 Submitted on 2 May 2019 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Improving the accuracy of the numerical values of the estimates some fundamental physical constants. Valery F. Timkov1*, Serg V. Timkov2, Vladimir A. Zhukov2, Konstantin E. Afanasiev2 1Institute of Telecommunications and Global Geoinformation Space of the National Academy of Sciences of Ukraine, Senior Researcher, Ukraine. 2Research and Production Enterprise «TZHK», Researcher, Ukraine. *Email: [email protected] The list of designations in the text: l -
APPENDICES 206 Appendices
AAPPENDICES 206 Appendices CONTENTS A.1 Units 207-208 A.2 Abbreviations 209 SUMMARY A description is given of the units used in this thesis, and a list of frequently used abbreviations with the corresponding term is given. Units Description of units used in this thesis and conversion factors for A.1 transformation into other units The formulas and properties presented in this thesis are reported in atomic units unless explicitly noted otherwise; the exceptions to this rule are energies, which are most frequently reported in kcal/mol, and distances that are normally reported in Å. In the atomic units system, four frequently used quantities (Planck’s constant h divided by 2! [h], mass of electron [me], electron charge [e], and vacuum permittivity [4!e0]) are set explicitly to 1 in the formulas, making these more simple to read. For instance, the Schrödinger equation for the hydrogen atom is in SI units: È 2 e2 ˘ Í - h —2 - ˙ f = E f (1) ÎÍ 2me 4pe0r ˚˙ In atomic units, it looks like: È 1 1˘ - —2 - f = E f (2) ÎÍ 2 r ˚˙ Before a quantity can be used in the atomic units equations, it has to be transformed from SI units into atomic units; the same is true for the quantities obtained from the equations, which can be transformed from atomic units into SI units. For instance, the solution of equation (2) for the ground state of the hydrogen atom gives an energy of –0.5 atomic units (Hartree), which can be converted into other units quite simply by multiplying with the appropriate conversion factor (see table A.1.1). -
Gauss' Theorem (See History for Rea- Son)
Gauss’ Law Contents 1 Gauss’s law 1 1.1 Qualitative description ......................................... 1 1.2 Equation involving E field ....................................... 1 1.2.1 Integral form ......................................... 1 1.2.2 Differential form ....................................... 2 1.2.3 Equivalence of integral and differential forms ........................ 2 1.3 Equation involving D field ....................................... 2 1.3.1 Free, bound, and total charge ................................. 2 1.3.2 Integral form ......................................... 2 1.3.3 Differential form ....................................... 2 1.4 Equivalence of total and free charge statements ............................ 2 1.5 Equation for linear materials ...................................... 2 1.6 Relation to Coulomb’s law ....................................... 3 1.6.1 Deriving Gauss’s law from Coulomb’s law .......................... 3 1.6.2 Deriving Coulomb’s law from Gauss’s law .......................... 3 1.7 See also ................................................ 3 1.8 Notes ................................................. 3 1.9 References ............................................... 3 1.10 External links ............................................. 3 2 Electric flux 4 2.1 See also ................................................ 4 2.2 References ............................................... 4 2.3 External links ............................................. 4 3 Ampère’s circuital law 5 3.1 Ampère’s original -
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International Journal of Theoretical and Mathematical Physics 2021, 11(1): 29-59 DOI: 10.5923/j.ijtmp.20211101.03 Measurement Quantization Describes the Physical Constants Jody A. Geiger 1Department of Research, Informativity Institute, Chicago, IL, USA Abstract It has been a long-standing goal in physics to present a physical model that may be used to describe and correlate the physical constants. We demonstrate, this is achieved by describing phenomena in terms of Planck Units and introducing a new concept, counts of Planck Units. Thus, we express the existing laws of classical mechanics in terms of units and counts of units to demonstrate that the physical constants may be expressed using only these terms. But this is not just a nomenclature substitution. With this approach we demonstrate that the constants and the laws of nature may be described with just the count terms or just the dimensional unit terms. Moreover, we demonstrate that there are three frames of reference important to observation. And with these principles we resolve the relation of the physical constants. And we resolve the SI values for the physical constants. Notably, we resolve the relation between gravitation and electromagnetism. Keywords Measurement Quantization, Physical Constants, Unification, Fine Structure Constant, Electric Constant, Magnetic Constant, Planck’s Constant, Gravitational Constant, Elementary Charge ground state orbital a0 and mass of an electron me – both 1. Introduction measures from the 2018 CODATA – we resolve fundamental length l . And we continue with the resolution of We present expressions, their calculation and the f the gravitational constant G, Planck’s reduced constant ħ corresponding CODATA [1,2] values in Table 1.