What Are Electromagnetic Fields?
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Electromagnetism As Quantum Physics
Electromagnetism as Quantum Physics Charles T. Sebens California Institute of Technology May 29, 2019 arXiv v.3 The published version of this paper appears in Foundations of Physics, 49(4) (2019), 365-389. https://doi.org/10.1007/s10701-019-00253-3 Abstract One can interpret the Dirac equation either as giving the dynamics for a classical field or a quantum wave function. Here I examine whether Maxwell's equations, which are standardly interpreted as giving the dynamics for the classical electromagnetic field, can alternatively be interpreted as giving the dynamics for the photon's quantum wave function. I explain why this quantum interpretation would only be viable if the electromagnetic field were sufficiently weak, then motivate a particular approach to introducing a wave function for the photon (following Good, 1957). This wave function ultimately turns out to be unsatisfactory because the probabilities derived from it do not always transform properly under Lorentz transformations. The fact that such a quantum interpretation of Maxwell's equations is unsatisfactory suggests that the electromagnetic field is more fundamental than the photon. Contents 1 Introduction2 arXiv:1902.01930v3 [quant-ph] 29 May 2019 2 The Weber Vector5 3 The Electromagnetic Field of a Single Photon7 4 The Photon Wave Function 11 5 Lorentz Transformations 14 6 Conclusion 22 1 1 Introduction Electromagnetism was a theory ahead of its time. It held within it the seeds of special relativity. Einstein discovered the special theory of relativity by studying the laws of electromagnetism, laws which were already relativistic.1 There are hints that electromagnetism may also have held within it the seeds of quantum mechanics, though quantum mechanics was not discovered by cultivating those seeds. -
The Lorentz Force
CLASSICAL CONCEPT REVIEW 14 The Lorentz Force We can find empirically that a particle with mass m and electric charge q in an elec- tric field E experiences a force FE given by FE = q E LF-1 It is apparent from Equation LF-1 that, if q is a positive charge (e.g., a proton), FE is parallel to, that is, in the direction of E and if q is a negative charge (e.g., an electron), FE is antiparallel to, that is, opposite to the direction of E (see Figure LF-1). A posi- tive charge moving parallel to E or a negative charge moving antiparallel to E is, in the absence of other forces of significance, accelerated according to Newton’s second law: q F q E m a a E LF-2 E = = 1 = m Equation LF-2 is, of course, not relativistically correct. The relativistically correct force is given by d g mu u2 -3 2 du u2 -3 2 FE = q E = = m 1 - = m 1 - a LF-3 dt c2 > dt c2 > 1 2 a b a b 3 Classically, for example, suppose a proton initially moving at v0 = 10 m s enters a region of uniform electric field of magnitude E = 500 V m antiparallel to the direction of E (see Figure LF-2a). How far does it travel before coming (instanta> - neously) to rest? From Equation LF-2 the acceleration slowing the proton> is q 1.60 * 10-19 C 500 V m a = - E = - = -4.79 * 1010 m s2 m 1.67 * 10-27 kg 1 2 1 > 2 E > The distance Dx traveled by the proton until it comes to rest with vf 0 is given by FE • –q +q • FE 2 2 3 2 vf - v0 0 - 10 m s Dx = = 2a 2 4.79 1010 m s2 - 1* > 2 1 > 2 Dx 1.04 10-5 m 1.04 10-3 cm Ϸ 0.01 mm = * = * LF-1 A positively charged particle in an electric field experiences a If the same proton is injected into the field perpendicular to E (or at some angle force in the direction of the field. -
Electromagnetic Field Theory
Lecture 4 Electromagnetic Field Theory “Our thoughts and feelings have Dr. G. V. Nagesh Kumar Professor and Head, Department of EEE, electromagnetic reality. JNTUA College of Engineering Pulivendula Manifest wisely.” Topics 1. Biot Savart’s Law 2. Ampere’s Law 3. Curl 2 Releation between Electric Field and Magnetic Field On 21 April 1820, Ørsted published his discovery that a compass needle was deflected from magnetic north by a nearby electric current, confirming a direct relationship between electricity and magnetism. 3 Magnetic Field 4 Magnetic Field 5 Direction of Magnetic Field 6 Direction of Magnetic Field 7 Properties of Magnetic Field 8 Magnetic Field Intensity • The quantitative measure of strongness or weakness of the magnetic field is given by magnetic field intensity or magnetic field strength. • It is denoted as H. It is a vector quantity • The magnetic field intensity at any point in the magnetic field is defined as the force experienced by a unit north pole of one Weber strength, when placed at that point. • The magnetic field intensity is measured in • Newtons/Weber (N/Wb) or • Amperes per metre (A/m) or • Ampere-turns / metre (AT/m). 9 Magnetic Field Density 10 Releation between B and H 11 Permeability 12 Biot Savart’s Law 13 Biot Savart’s Law 14 Biot Savart’s Law : Distributed Sources 15 Problem 16 Problem 17 H due to Infinitely Long Conductor 18 H due to Finite Long Conductor 19 H due to Finite Long Conductor 20 H at Centre of Circular Cylinder 21 H at Centre of Circular Cylinder 22 H on the axis of a Circular Loop -
Electro Magnetic Fields Lecture Notes B.Tech
ELECTRO MAGNETIC FIELDS LECTURE NOTES B.TECH (II YEAR – I SEM) (2019-20) Prepared by: M.KUMARA SWAMY., Asst.Prof Department of Electrical & Electronics Engineering MALLA REDDY COLLEGE OF ENGINEERING & TECHNOLOGY (Autonomous Institution – UGC, Govt. of India) Recognized under 2(f) and 12 (B) of UGC ACT 1956 (Affiliated to JNTUH, Hyderabad, Approved by AICTE - Accredited by NBA & NAAC – ‘A’ Grade - ISO 9001:2015 Certified) Maisammaguda, Dhulapally (Post Via. Kompally), Secunderabad – 500100, Telangana State, India ELECTRO MAGNETIC FIELDS Objectives: • To introduce the concepts of electric field, magnetic field. • Applications of electric and magnetic fields in the development of the theory for power transmission lines and electrical machines. UNIT – I Electrostatics: Electrostatic Fields – Coulomb’s Law – Electric Field Intensity (EFI) – EFI due to a line and a surface charge – Work done in moving a point charge in an electrostatic field – Electric Potential – Properties of potential function – Potential gradient – Gauss’s law – Application of Gauss’s Law – Maxwell’s first law, div ( D )=ρv – Laplace’s and Poison’s equations . Electric dipole – Dipole moment – potential and EFI due to an electric dipole. UNIT – II Dielectrics & Capacitance: Behavior of conductors in an electric field – Conductors and Insulators – Electric field inside a dielectric material – polarization – Dielectric – Conductor and Dielectric – Dielectric boundary conditions – Capacitance – Capacitance of parallel plates – spherical co‐axial capacitors. Current density – conduction and Convection current densities – Ohm’s law in point form – Equation of continuity UNIT – III Magneto Statics: Static magnetic fields – Biot‐Savart’s law – Magnetic field intensity (MFI) – MFI due to a straight current carrying filament – MFI due to circular, square and solenoid current Carrying wire – Relation between magnetic flux and magnetic flux density – Maxwell’s second Equation, div(B)=0, Ampere’s Law & Applications: Ampere’s circuital law and its applications viz. -
Estimating Fire Properties by Remote Sensing
Estimating Fire Properties by Remote Sensing1. Philip J. Riggan USDA Forest Service Pacific Southwest Research Station 4955 Canyon Crest Drive Riverside, CA 92507 909 680 1534 [email protected] James W. Hoffman Space Instruments, Inc. 4403 Manchester Avenue, Suite 203 Encinitas, CA 92024 760 944 7001 [email protected] James A. Brass NASA Ames Research Center Moffett Federal Airfield, CA 94035 650 604 5232 [email protected] Abstract---Contemporary knowledge of the role of fire in the TABLE OF CONTENTS global environment is limited by inadequate measurements of the extent and impact of individual fires. Observations by 1. INTRODUCTION operational polar-orbiting and geostationary satellites provide an 2. ESTIMATING FIRE PROPERTIES indication of fire occurrence but are ill-suited for estimating the 3. ESTIMATES FROM TWO CHANNELS temperature, area, or radiant emissions of active wildland and 4. MULTI-SPECTRAL FIRE IMAGING agricultural fires. Simulations here of synthetic remote sensing 5. APPLICATIONS FOR FIRE MONITORING pixels comprised of observed high resolution fire data together with ash or vegetation background demonstrate that fire properties including flame temperature, fractional area, and INTRODUCTION radiant-energy flux can best be estimated from concurrent radiance measurements at wavelengths near 1.6, 3.9, and 12 µm, More than 30,000 fire observations were recorded over central Successful observations at night may be made at scales to at Brazil during August 1999 by Advanced Very High Resolution least I km for the cluster of fire data simulated here. During the Radiometers operating aboard polarorbiting satellites of the U.S. daytime, uncertainty in the composition of the background and National Oceanic and Atmospheric Administration. -
Chapter 22 Magnetism
Chapter 22 Magnetism 22.1 The Magnetic Field 22.2 The Magnetic Force on Moving Charges 22.3 The Motion of Charged particles in a Magnetic Field 22.4 The Magnetic Force Exerted on a Current- Carrying Wire 22.5 Loops of Current and Magnetic Torque 22.6 Electric Current, Magnetic Fields, and Ampere’s Law Magnetism – Is this a new force? Bar magnets (compass needle) align themselves in a north-south direction. Poles: Unlike poles attract, like poles repel Magnet has NO effect on an electroscope and is not influenced by gravity Magnets attract only some objects (iron, nickel etc) No magnets ever repel non magnets Magnets have no effect on things like copper or brass Cut a bar magnet-you get two smaller magnets (no magnetic monopoles) Earth is like a huge bar magnet Figure 22–1 The force between two bar magnets (a) Opposite poles attract each other. (b) The force between like poles is repulsive. Figure 22–2 Magnets always have two poles When a bar magnet is broken in half two new poles appear. Each half has both a north pole and a south pole, just like any other bar magnet. Figure 22–4 Magnetic field lines for a bar magnet The field lines are closely spaced near the poles, where the magnetic field B is most intense. In addition, the lines form closed loops that leave at the north pole of the magnet and enter at the south pole. Magnetic Field Lines If a compass is placed in a magnetic field the needle lines up with the field. -
The Electromagnetic Spectrum
The Electromagnetic Spectrum Wavelength/frequency/energy MAP TAP 2003-2004 The Electromagnetic Spectrum 1 Teacher Page • Content: Physical Science—The Electromagnetic Spectrum • Grade Level: High School • Creator: Dorothy Walk • Curriculum Objectives: SC 1; Intro Phys/Chem IV.A (waves) MAP TAP 2003-2004 The Electromagnetic Spectrum 2 MAP TAP 2003-2004 The Electromagnetic Spectrum 3 What is it? • The electromagnetic spectrum is the complete spectrum or continuum of light including radio waves, infrared, visible light, ultraviolet light, X- rays and gamma rays • An electromagnetic wave consists of electric and magnetic fields which vibrates thus making waves. MAP TAP 2003-2004 The Electromagnetic Spectrum 4 Waves • Properties of waves include speed, frequency and wavelength • Speed (s), frequency (f) and wavelength (l) are related in the formula l x f = s • All light travels at a speed of 3 s 108 m/s in a vacuum MAP TAP 2003-2004 The Electromagnetic Spectrum 5 Wavelength, Frequency and Energy • Since all light travels at the same speed, wavelength and frequency have an indirect relationship. • Light with a short wavelength will have a high frequency and light with a long wavelength will have a low frequency. • Light with short wavelengths has high energy and long wavelength has low energy MAP TAP 2003-2004 The Electromagnetic Spectrum 6 MAP TAP 2003-2004 The Electromagnetic Spectrum 7 Radio waves • Low energy waves with long wavelengths • Includes FM, AM, radar and TV waves • Wavelengths of 10-1m and longer • Low frequency • Used in many -
Equivalence of Current–Carrying Coils and Magnets; Magnetic Dipoles; - Law of Attraction and Repulsion, Definition of the Ampere
GEOPHYSICS (08/430/0012) THE EARTH'S MAGNETIC FIELD OUTLINE Magnetism Magnetic forces: - equivalence of current–carrying coils and magnets; magnetic dipoles; - law of attraction and repulsion, definition of the ampere. Magnetic fields: - magnetic fields from electrical currents and magnets; magnetic induction B and lines of magnetic induction. The geomagnetic field The magnetic elements: (N, E, V) vector components; declination (azimuth) and inclination (dip). The external field: diurnal variations, ionospheric currents, magnetic storms, sunspot activity. The internal field: the dipole and non–dipole fields, secular variations, the geocentric axial dipole hypothesis, geomagnetic reversals, seabed magnetic anomalies, The dynamo model Reasons against an origin in the crust or mantle and reasons suggesting an origin in the fluid outer core. Magnetohydrodynamic dynamo models: motion and eddy currents in the fluid core, mechanical analogues. Background reading: Fowler §3.1 & 7.9.2, Lowrie §5.2 & 5.4 GEOPHYSICS (08/430/0012) MAGNETIC FORCES Magnetic forces are forces associated with the motion of electric charges, either as electric currents in conductors or, in the case of magnetic materials, as the orbital and spin motions of electrons in atoms. Although the concept of a magnetic pole is sometimes useful, it is diácult to relate precisely to observation; for example, all attempts to find a magnetic monopole have failed, and the model of permanent magnets as magnetic dipoles with north and south poles is not particularly accurate. Consequently moving charges are normally regarded as fundamental in magnetism. Basic observations 1. Permanent magnets A magnet attracts iron and steel, the attraction being most marked close to its ends. -
Permanent Magnet Design Guidelines
NOTE(2019): THIS ORGANIZATION (MMPA) IS OBSOLETE! MAGNET GUIDELINES Basic physics of magnet materials II. Design relationships, figures merit and optimizing techniques Ill. Measuring IV. Magnetizing Stabilizing and handling VI. Specifications, standards and communications VII. Bibliography INTRODUCTION This guide is a supplement to our MMPA Standard No. 0100. It relates the information in the Standard to permanent magnet circuit problems. The guide is a bridge between unit property data and a permanent magnet component having a specific size and geometry in order to establish a magnetic field in a given magnetic circuit environment. The MMPA 0100 defines magnetic, thermal, physical and mechanical properties. The properties given are descriptive in nature and not intended as a basis of acceptance or rejection. Magnetic measure- ments are difficult to make and less accurate than corresponding electrical mea- surements. A considerable amount of detailed information must be exchanged between producer and user if magnetic quantities are to be compared at two locations. MMPA member companies feel that this publication will be helpful in allowing both user and producer to arrive at a realistic and meaningful specifica- tion framework. Acknowledgment The Magnetic Materials Producers Association acknowledges the out- standing contribution of Parker to this and designers and manufacturers of products usingpermanent magnet materials. Parker the Technical Consultant to MMPA compiled and wrote this document. We also wish to thank the Standards and Engineering Com- mittee of MMPA which reviewed and edited this document. December 1987 3M July 1988 5M August 1996 December 1998 1 M CONTENTS The guide is divided into the following sections: Glossary of terms and conversion A very important starting point since the whole basis of communication in the magnetic material industry involves measurement of defined unit properties. -
Hydraulics Manual Glossary G - 3
Glossary G - 1 GLOSSARY OF HIGHWAY-RELATED DRAINAGE TERMS (Reprinted from the 1999 edition of the American Association of State Highway and Transportation Officials Model Drainage Manual) G.1 Introduction This Glossary is divided into three parts: · Introduction, · Glossary, and · References. It is not intended that all the terms in this Glossary be rigorously accurate or complete. Realistically, this is impossible. Depending on the circumstance, a particular term may have several meanings; this can never change. The primary purpose of this Glossary is to define the terms found in the Highway Drainage Guidelines and Model Drainage Manual in a manner that makes them easier to interpret and understand. A lesser purpose is to provide a compendium of terms that will be useful for both the novice as well as the more experienced hydraulics engineer. This Glossary may also help those who are unfamiliar with highway drainage design to become more understanding and appreciative of this complex science as well as facilitate communication between the highway hydraulics engineer and others. Where readily available, the source of a definition has been referenced. For clarity or format purposes, cited definitions may have some additional verbiage contained in double brackets [ ]. Conversely, three “dots” (...) are used to indicate where some parts of a cited definition were eliminated. Also, as might be expected, different sources were found to use different hyphenation and terminology practices for the same words. Insignificant changes in this regard were made to some cited references and elsewhere to gain uniformity for the terms contained in this Glossary: as an example, “groundwater” vice “ground-water” or “ground water,” and “cross section area” vice “cross-sectional area.” Cited definitions were taken primarily from two sources: W.B. -
Electric and Magnetic Fields the Facts
PRODUCED BY ENERGY NETWORKS ASSOCIATION - JANUARY 2012 electric and magnetic fields the facts Electricity plays a central role in the quality of life we now enjoy. In particular, many of the dramatic improvements in health and well-being that we benefit from today could not have happened without a reliable and affordable electricity supply. Electric and magnetic fields (EMFs) are present wherever electricity is used, in the home or from the equipment that makes up the UK electricity system. But could electricity be bad for our health? Do these fields cause cancer or any other disease? These are important and serious questions which have been investigated in depth during the past three decades. Over £300 million has been spent investigating this issue around the world. Research still continues to seek greater clarity; however, the balance of scientific evidence to date suggests that EMFs do not cause disease. This guide, produced by the UK electricity industry, summarises the background to the EMF issue, explains the research undertaken with regard to health and discusses the conclusion reached. Electric and Magnetic Fields Electric and magnetic fields (EMFs) are produced both naturally and as a result of human activity. The earth has both a magnetic field (produced by currents deep inside the molten core of the planet) and an electric field (produced by electrical activity in the atmosphere, such as thunderstorms). Wherever electricity is used there will also be electric and magnetic fields. Electric and magnetic fields This is inherent in the laws of physics - we can modify the fields to some are inherent in the laws of extent, but if we are going to use electricity, then EMFs are inevitable. -
X-Ray Production Compton Scattering Pair Production
Welcome back to PHY 3305 Today’s Lecture: X-ray Production Compton Scattering Pair Production Arthur Compton 1892 - 1962 Physics 3305 - Modern Physics Professor Jodi Cooley Meeting of the Texas Section of the American Physical Society When: Fri-Sat Oct 20-21 Where: UT Dallas ñ Physics majors are expected to attend, and present any research project if applicable. ñ See the email from Dr. Dalley about registration (deadline Sept 27). ñ See Michele Hill (Physics office) well before the meeting to get set up for registration and banquet fee reimbursement. Physics 3305 - Modern Physics Professor Jodi Cooley Anouncements • Reading Assignment: Chapter 3.6; 4.1 - 4.2 • Problem set 5 is due Tuesday, Sept. 26th at 12:30 pm. • Regrade for problem set 4 is due Tuesday, Sept 26th at 12:30 pm. • Midterm exam 1 covering chapters 1-2 and related material will be in class on Thursday, Sept 21st. There will be a seating chart. Physics 3305 - Modern Physics Professor Jodi Cooley Review Question 1 In a photoelectric effect experiment, if the intensity of the incident light is doubled the stopping potential will: a) Double b) Double, but only of if the light’s frequency is above the cut-off Current between the electrodes c) Half stops when the opposing potential energy difference equals the d) Remain unchanged maximum KE of the photoelectrons. KE = hf φ max − Physics 3305 - Modern Physics Professor Jodi Cooley Electrons are accelerated in television tubes through a potential difference of 10.0 kV. Find the lowest wavelength of the electromagnetic waves emitted when these electrons strike the screen.