PHY 417G: Introduction

1. PHY 417G: Introduction Christopher Crawford 2015-01-14

2. Outline • Announcements Syllabus; schedule: HW due, recitations Grades – distribution, Feedback – discussion REU opportunities – ex: accelerator physics • Introduction Ridiculously brief history of E&M Math review: linear + differential spaces, fund. theorems E&Mreview/overview: mathematical structure

3. Announcements • Syllabus: pa.uky.edu  about  courses  417 • HW schedule: recitations?, due day? Office hours? Exams? • Grades: Final Grade Final Exam • Feedback • Your participation in class changes everything! • REU positions • http://www.anl.gov/education/undergraduates/internship-opportunities/lee-teng-undergraduate-fellowship-accelerator

4. History of magnetism • The magnetic force was known in antiquity • Magnetism more predominant in nature but more difficult to quantify: • Permanent magnets (magnetization), not electric currents • No magnetic (point) charge (monopole) –> dipole effect (N,S poles) • 1-d currents instead of 0-d charges –> can’t split a wire! • Static electricity produced in the lab long before steady currents • Timeline (from “A Ridiculous Brief History of Electricity and Magnetism”) • 600 BC Thales of Miletus discovers lodestone’s attraction to iron • 1200 AD Chinese use lodestone compass for navigation • 1259 AD Petrus Peregrinus (Italy) discovers the same thing • 1600 AD William Gilbert discovers that the Earth is a giant magnet • 1742 AD Thomas LeSeur shows inverse cube law for magnets • 1820 AD Hans Christian Ørsted discovers that current twists magnets Andre Marie Ampere shows that parallel currents attract/repel Jean-Baptiste Biot & Felix Savart show inverse square law

5. Unification of 4 Fundamental Forces

6. Classical Fields • action at a distance vs. locality • field ”mediates “carries force • extends to quantum field theories • field is everywhere always E (x, t) • differentiable, integrable • field lines, equipotentials • powerful techniques • for solving complex problems

7. Magnetic fields • In magnetism it is more natural to start with the concept of “Magnetic field” than the actual force law! (dipole) • Compass alignswith B-field • Iron filings lineup along magneticfield lines • Magnetic field lines look like an electric dipole (in fact the magnetic dipole was discovered first!)

8. Difference between E, B dipoles • Same as the differences between Flux and Flow! • Charge = sources of flux • Conservative flow [potential] • Example: Amber (electric) • Rub to charge • 2 charges (+/–) “monopole fluids” • Exerts force on charges • Continuous field lines [flux] • Rotational (source of flow?) • Example: Lodestone (magnet) • Always charged • 2 poles (N/S) “inseparable dipole” • Exerts torque on other magnets

9. Formulations of E & M • Electricity Magnetism • Note the interchange of flux and flow: twisted symmetry!

10. Magnetic scalar potential Electrostatics – Coulomb’s law Magnetostatics – Biot-Savart law B.C.’s:Flux lines bounded by charge Flux lines continuous Flow sheets continuous (equipotentials) Flow sheets bounded by current

11. L/T separation of E&M fields

12. Equations of Electrodynamics

13. Polarization & Magnetization • Chapter 4: electric materials –> Chapter 6: magnetic materials • Polarization chain –> Magnetization mesh

14. 3 Materials –> 3 Components • Materials constants: permittivity, resistivity, permeability • Electrical components: capacitor, resistor, inductor • Each is a ratio of Flux / Flow !