# Physics 303 Classical fields / Electrodynamics

## Syllabus, Spring 2012

We meet at noon, MWF in SC 203.

### On the web

You can find the syllabus and other materials related to this course on the web at:
goshen.edu/fields , or
goshen.edu/physix/303 .

Grades will be available on moodle.goshen.edu.

I use your "goshen.edu" e-mail address for class communications. Some of you may use other e-mail services. If you do use some other service, make sure your goshen.edu e-mail account is set up to forward e-mail to the account you read most often. (Zimbra: Preferences > Mail)

### Instructor

Paul Meyer Reimer

Sci 011   ·   x7318   ·   gvoice: 312-3395   ·   e-mail: paulmr@goshen.edu

### Overview

The classical theory of electric and magnetic fields is developed using vector calculus. Topics include dielectric and magnetic materials, Maxwell's field equations, and electromagnetic waves. Prerequisites: Phys 203-204-General Physics I and II.

This is a 3 credit hour course. The College expectation is that you are spending 2-4 hours outside class for every hour in class.

### Texts and Tools

#### Required

David J. Griffiths. Introduction to Electrodynamics (3rd edition).  Prentice Hall, 1999.

Mathematica: You'll need to use a computer algebra system like Maple or Mathematica to visualize and solve some homework problems and potentially exam questions. You don't have to buy one: GC has a site license for Mathematica which is available on GC lab computers.

 homework 28% problem writeups (2) 8% 2 exams 38% final exam 23% participation 3%

A > 90%
B 80-89%
C 70-79%
D 60-69%
F < 60%

I may adjust this scheme down a bit (e.g. 89% might end up being good enough for an A), but I certainly won't adjust it up.

#### Homework

Working through the homework is perhaps more important for your learning than anything we do in class. Everyone will hand in their own write-up of each homework problem. But I encourage you to work through homework problems with others in the class.

Unless otherwise indicated, problems are from Griffiths' textbook.

#### Problem writeups

These comprise two short writing assignments.

Chose two problems to write up in more detail. These should be:

• less-than-trivial problems from the ones at the end of chapters.
• Not problems that were assigned for another purpose.
• You must pick your own problem: No two people will work the same problem. You *may* consult other people about your problem.

You'll use Mathematica to write up a solution with equations, diagrams as appropriate, and text which explains the approach you took to the problem, and references the physical principles you're using. Like (some) writing assignments from other classes, you'll hand in a first draft of this, and after feedback, a final draft. The rubric used to grade this comprises these categories:

• Exposition of the problem - Copy out the statement of the problem. Use a different font to visually distinguish your work from the specification of the problem. Label the problem with chapter and problem number.

• Diagrams and plots - Use a diagram to sketch out the physical system, and label the names of quantities (angles, coordinates, etc). You may hand draw this! Include plots of functions as appropriate, for example to indicate maxima or minima, or equipotentials, or a potential energy surface, or otherwise enlighten the problem in some way.

• Grammar and spelling - Use a more formal voice than when speaking, e.g. "a maxima" not "a max", "substitute in" rather than "plug in". Punctuation in physics papers is a unique issue. You should punctuate equations as if they were any other part of your writing: periods or commas frequently go at the end of a displayed equation.

• Correctness of your solution - Gotta make sure you do the problem right! See if you can do some sort of "sanity check" on your results as you go along.

• Clarity of narration - Think of your audience as other students in this class, with some general familiarity with the material. Name the principles and techniques you're using to solve the problem at each section of your problem. You may refer to equations in the textbook: give some context to say where such an equation comes from.

It is a common error to take for granted the vector nature of key quantities. The electric field is *always* a vector field with 3 components that depend on the 3 components of position (and possibly time as well: $\myv E(\myv r)$. We frequently make symmetry arguments to argue that the electric field has some simpler form. For example, the field around a charge at the origin has spherical symmetry, which means that $\myv E(r,\theta,\phi) = E_r(r) \uv r$. Once you point this out, you can start throwing around "$E(r)$" but not before you point out how $E(r)$ is related to the full vector field.

• Math typesetting / notation - Use real subscripts (not t0 when you mean $t_0$). Figure out how to get greek letters in Mathematica. (Esc-a-esc results in $\alpha$. Esc-q-esc $\to \theta$. Distinguish visually between vector and scalar quantities: scalars are usually displayed as non-bold italic quantities (Mathematica should do this automatically in math mode). Vector quantities are generally non-italic, and either have a little arrow over them, e.g. $\myv{b}$, or else appear as bold face, e.g. $\bf{b}$. Mathematica commands will generally appear as a monospaced font like this "Plot[ Sin[x],......]" without you having to do anything special. When displaying definite integrals, use the ' notation to distinguish between the integration variable and the integration limits, e.g. $$\int_{v_0}^{v(t)} \frac{dv'}{F(v')}.$$ It may be useful to number equations to refer back to them, or put in a hand lettered "star" or other convenient symbol beside one that you wish to refer back to.

#### Image credits

WileyMCB - Maya Lin's Storm King Wavefield.