Talk:Electrodynamics


 * "In this section we will begin by stating the basic equations of electromagnetism --in terms of the four-potential, valid in special relativity-- then see how this reduces to the simple rules governing electricity and magnetism we learnt in school.


 * "Approaching the subject this way means you will be aware of the appproximations in the simple rules."

Unlike like the standard approach, where every five chapters you say "Sorry, what we told you earlier was only half-true. This is the real story."

Approaching the subject from this angle has advantages, especially as part of a unified treatment of modern physics (and it's the approach taken by the source text) so I'd suggest we try sticking to it. The traditional approach can be used in other wikibooks, giving the readers a chance to see which suits them best. Carandol

Maxwell's
Which chapter will cover Maxwells. On another note, I just finished a first draft of Four-Potentials

Discouraged Teaching Method
Teaching physics with this top-down approach should, in my opinion, be thoroughly discouraged for the following reasons:

1. It isn't really the top in the first place. At higher energy scales, electromagnetism seems to descend from the superstructure of Electroweak interactions as a low-energy limit. So, starting with four potentials would be a rather abrupt checkpoint of the theory to start with.

2. While it is true that the theory in terms of four potentials is mathematically elegant and forces an impression of inevitability, this formalism is invisible to many physical possibilites such as that of the magnetic monopole. A person studying the EM formalism through four potentials loses the chance to think about such possibilities or what experiments could be done to detect them.

3. Physics is an emperical science. It is dictated by experiment. Close correspondences between experimental findings and some mathematical structures lend those mathematical structures temporary importance in our understanding of the physical world. To begin a discussion of electromagnetism (aimed at the lay reader / sophomore visiting Wiki) with head-in-the-air formalism that aims to descend and explain all electromagnetic phenomena will deprive people of real reasons for the development of electric and magnetic fields to explain phenomena in the world. Otherwise, all the A's and F's are just an academic exercise in mental gymnastics.

4. The four potential, in quantum electrodynamics, leads to some rather knotty problems of gauge fixing (solved, but rather messily). This gauge freedom in A and its messy fixing in QED lead us to believe that we lack a respectable gauge free notation of electrodynamics.

I suspect that you might have had a largely mathematics based background going into electromagnetism because I see that you try to start from Lorentz invariance etc and are struck by its mathematical simplicity. You could also, begin from the deeper quantum theory of electrodynamics of A and descend to explain all physical phenomena pretty successfully. That will be the best picture we have so far, but at what cost to the general reader or curious character? However, if you still wish to expound EM top down, I would suggest looking for a two form of A to make a Lorentz invariant Lagrangian and proceed down.

I believe this is a thorougly misguided approach to teaching anything, and will potentially befuddle the general reader instead of providing him with an honest understanding of what we know and how we know.

Response
I agree with you but came to help this wikibook after the format was already laid out. If you read my Four Potential stuff you'll probably note that I keep throwing off telling people to study the rest first. If you would like to suggest a better format here, I would be most pleased to implement it after a vote. --Frontier 00:49, 8 Apr 2005 (UTC)

Section Structure
I've been trying to contribute to these pages, and I am finding that their structure is inconducive to adding material in any kind of sensible progression. Starting the discussion off with electromagnetic four-potential is a strange idea (at best), especially considering the book hasnt even discussed elementary currents or potentials before hand. I've rearranged some of the existing pages into a progression that (i feel) will be better and more straight-forward for a reader without much familiarity with the subject. However, despite my best efforts at rearranging, I can't quite seem to make pages line up to provide material in a good order. Therefore, I am going to propose an outline for a proposed new architecture to this section, and I would like to get some questions/comments on this before I do it:


 * Introduction
 * required maths (vectors, del, flux, divergance, curl, spherical coordinates, etc...)
 * Electrostatics
 * Coulomb's Law
 * E-Field
 * Gauss' Law
 * Conservation of E-Field (Electric potential, charge distribution energy)
 * Capacitance
 * Relativity
 * Michelson-Morley Experiment
 * Lorentz Transformation
 * Four-Vectors
 * Magentic Fields
 * E and B fields as Tensors
 * Maxwell's Equations
 * Magnetostatics
 * Ohms Law
 * Biot-Savart's Law
 * Ampere's Law
 * Magentization
 * Mechanics
 * Force and Torque by E and B fields, etc.
 * Motions and interactions of charged particles
 * Larmor Precession
 * Magnetic Stress Tensors
 * Variation with Time
 * Faraday's Law
 * Poynting Vector
 * Displacement Current
 * Four-Vectors changing in Time

This is, I think, a good way to integrate all the material into a straight-forward precession. I can think of some things that can definately be moved around, however. I ask anybody who knows about this material to help out and make comments/suggestions on this outline, because I would like to start moving/renaming/deleting pages here to make things better ASAP. --Whiteknight (talk) (projects) 17:21, 3 July 2006 (UTC)

I would suggest moving relativity towards the bottom of the list and looking at Mechanics of Electricity directly after Electrostatics. From there Magnetism would come in as allegory to electricity, which seems to work well. I've just finished taking a class in this (PH 212/252 at most colleges), and this was the general layout. Essentially, this stuff is confusing as all get out, and it's somewhat easier to tackle if you do it one idea at a time and build slowly. Since magnetism behaves so similarly to electricity, it seems much easier to study it after one has some knowledge of electricity.

--Thatnerdyguy 15:40, 24 July 2006 (UTC)


 * I agree with you, i think. Although, the Special Relativity chapter of this book occurs before this chapter, so readers should have some background knowledge of it. This subject is sufficiently difficult, however, and maybe we should just push it off till the end. Magnetism is best learned (from my experiance as well) as an allegory for electricity, so we can worry about that second-to-last. --Whiteknight (talk) (projects) 16:36, 24 July 2006 (UTC)

Rename
This page needs to be renamed to electromagnetism... because it speaks not only of electrodynamics, but also electrostatic. ''Raylton P. Sousa qualquer coisa estou aqui! =D'' 02:22, 26 February 2011 (UTC)