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

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&M review/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

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 aligns with B-field
Iron filings line up along magnetic field 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
Geometrical Gauss -> Ampere’s law
U interpretation as boundary currents
Statement in terms of boundary conditions
Technique for calculating coils
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 !