Physics 401. Electromagnetic Theory (Electrodynamics)

Transcription

1 Physics 401 Electomagnetic Theoy (Electodynamics) Please ead handouts and see couse webpages fo moe info Class: Monday, Wednesday & Fiday 9:00-10:00 Henn 302 Pofesso: Janis McKenna Office: Hennings-Physics 262 Phone: My most often gets answeed evenings between 11pm and 1am. Office Hous: Tuesdays 16:00-17:00, o Thusdays 13:00-14:00 o by appointment (except not this week on Thusday). If you want to dop by with no appointment, thee s a decent chance of often finding me in my office aftenoons 4-5pm Januay 7, 2008 PHYS Lectue 1 1

2 Physics 401 Text: Intoduction to Electodynamics, 3d edition, by D. Giffiths If you'e looking fo moe: Electicity and Magnetism, by E.M.Pucell (slightly lowe level than Giffiths, vey nicely done) The Feynman Lectues on Physics Vol. 2, by Feynman, Leighton & Sands (geat book - one of my favouites ) Electomagnetic Fields and Waves by Loain and Coson (level simila to Giffiths) Classical Electodynamics, by J.D. Jackson (gaduate level E&M text - the classic ) Mathematical Methods fo Physicists, by Afken (geat efeence fo mathematics, vecto calculus, diffeential equations, special functions, coodinate systems, complex vaiable theoy, and a wide vaiety of applications in all fields of physics, including E&M ) Januay 7, 2008 PHYS Lectue 1 2

3 Outline of topics to be coveed * Review of Electostatics and Magnetostatics * Electomagnetic Induction * Maxwell s Equations * Electomagnetic Waves * Absoption and Dispesion * Waves in Waveguides * Radiation of Electomagnetic Waves * Potentials, Fields and Gauge Tansfomations * Electodynamics and Relativity You will find we will most of the mateial in Giffiths, Chaptes 7-12, plus a few topics fom outside the textbook, plus the topics you choose to cove in you pesentations. Januay 7, 2008 PHYS Lectue 1 3

4 Gading Scheme Gading: 40% Final Exam 20% Assignments (11 will be assigned ove the tem, you best 10 will count) 15% Midtem Exam 1 -- Fiday Febuay 15 15% Midtem Exam 2 -- Fiday Mach 28 10% Semina Pesentation and Essay/Witeup (5% semina, 5% witeup) Thee is no toleance fo late assignments without medical o tagic eason, as solutions will be posted on o the day afte due date. You ae encouaged to wok togethe and seek help fom each othe in doing the homewok: discussing the poblems in a study goup is a geat way to lean. But I expect each student to wite up (and undestand!) he/his own solutions handed in fo gading. When my WEBCT equest gets setup, I ll put up a class bulletin boad Januay 7, 2008 PHYS Lectue 1 4

5 Student Semina and Essay Semina Pesentation: Each student will investigate and shae with the class a shot semina on a topic of you choice (appoved by me - it has to have E&M elevance). The semina/oal epot will be an 8-9 minute semina-style pesentation in class, followed by 4-5 minutes of discussion and questions. All students pesent fo the semina will paticipate in evaluations. Wite-up/Essay: You essay will be a shot 4-6 page epot/wite-up based on you pesentation. I popose to hand out a hadcopy collection of all you essays if you give me in witing you pemission on the last page of you essay. I don t want to post any of this wok on the web, but athe make a hadcopy fo each egisteed classmate only. It will be like having confeence poceedings of pesentations 2008 s PHYS 401 Seminas. I plan to include a couple of quickie questions on the final on some of the mateial pesented by you. The epot is due Fiday Apil 11, Poceedings will be available fo you to pick up on Tuesday, Apil 15, Januay 7, 2008 PHYS Lectue 1 5

6 Natue: 4 basic foces E&M (my pespective) Stong Electomagnetic Weak Gavity A bit of paticle physics Januay 7, 2008 PHYS Lectue 1 6

7 E&M -fist step to Gand Unification Relativity: move a magnet geneate an electic cuent move an electic chage geneate a magnetic field Unified theoy of electicity and magnetism: Electodynamics THIS COURSE Tansfom a stationay chage with E field to anothe fame Get moving chage (a sot of cuent) and geneate a B field. Model fo gande unification (i.e. all 4 fundamental foces) The fact that Maxwell s theoy has this unification of E&M built into it was one of the clues Einstein picked up on and was pat of his motivation in the development of the Theoy of Special Relativity (1905). Januay 7, 2008 PHYS Lectue 1 7

8 E&M Review (this class and next) (o: what I hope you leaned in PHYS 301/354) Foces on electic chages: electic and magnetic Supeposition of vecto fields Electic field, electic potential: a vaiety of techniques in you toolbox to solve fo them Enegy and Wok Conductos Toolbox: (mathematical techniques to solve fo fields - I assume that you have vecto calculus and diffeential equations masteed ) Magnetic field due to steady cuent Mateials: polaizability and magnetization of mateials (electic and magnetic dipoles) Beginning of dynamics (i.e time-dependant fields) All above summaizes into Maxwell s equations Classical E&M waves cay enegy and momentum PHYS 401 picks up hee. Januay 7, 2008 PHYS Lectue 1 8

9 Review: Foces between fixed chages & cuents Units: SI units!(mks) used in Giffiths and in class ( engineeing units ) Electostatics q 1 q 2 (Coulomb s Law) F = 1 q 1 q 2 4πε 0 2 ˆ F q q Magnetostatics (Ampee s Law) I 1 I 2 F = µ 0 I 1 I 2 2π ˆ F I 1 I 2 Constants of popotionality depend on medium ε 0 = e 2 /Nm 2 Pemittivity of fee space µ 0 = 4π 10-7 N/A 2 Pemeability of fee space (many constants in Giffiths font & back coves - don t memoize!) Januay 7, 2008 PHYS Lectue 1 9

10 Review: Discete and Continuous Chage Distibutions In geneal, chage distibution densities λ, σ, ρ ae functions of position. BEWARE: don t confuse field point and souce point!!! Coulomb s Law: = '= (x x')ˆ i + (y y') ˆ j + (z z') k ˆ Line Chage: λ= chage/length dq= λ dl' E ( ) = 1 ') d l ˆ 4πε 0 λ( Suface Chage: σ= chage/aea dq= σ da' E ( ) = 1 Volume Chage: ρ=chage/volume dq= ρ dτ' Januay 7, 2008 PHYS Lectue σ( ') d a 4πε 0 2 E ( ) = 1 E ( ) = 1 4πε 0 ˆ ρ( ') d τ 4πε 0 2 dq 2 ˆ ˆ