Electricity, Magnetism, and Thermodynamics

Oberlin College Physics 111

Syllabus for Spring 2024

Learning goals: Through your work in this course, you will

But the primary goal of this course is not to make you remember that the electrical force between two charged particles falls off like the distance between them squared. The primary goal is to inspire you to be creative, take risks, and "boldly go where no one has gone before".

Classroom Teacher: Dan Styer, Wright 215, 440-775-8183, Dan.Styer@oberlin.edu
home telephone 440-281-1348 (9:00 am to 8:00 pm only). Instructions for meeting with me are given under "Schedule" here.

Pronouns, nouns, adjectives, and the character of science: I don't care what pronouns you use when referring to me. Similarly, you may call me "Dan", or "Mr. Styer", or "Dr. Styer", or "Prof. Styer", whichever you find most comfortable. My personal preference, however, is that you call me "Dan". In this course I will present upsetting conclusions violently opposed to our common sense and common experience. (For example: That electrical energy can flow from one circuit and into another without passing through wires. That light added to light can sum to darkness. I make no apologies for presenting upsetting conclusions: An education that avoids difficult or disturbing issues is no education at all.) I hope you'll accept those conclusions because they are based on experimental evidence and on cogent, clear, fact-based reasoning -- experiments and reasoning that you or I or anyone else could execute. If you accept those conclusions instead because I have earned the right to put a fancy shingle in front of my name, my teaching will have been an abject failure.

Laboratory Teacher: Bryan Terrazas, Wright 211, bterraza@oberlin.edu, office hours Mondays 2:00 to 3:00 pm or by appointment.

Meeting times: Class: Monday, Wednesday, and Friday at 9:00 am at Wright Laboratory room 201.
Conference: (optional) Tuesday at 11:00 am at Wright Laboratory room 209.
Laboratory: Tuesday, Wednesday, or Thursday at 1:30 pm at Wright Laboratory room 214.
(The first lab will be a brief orientation on the week of 5 February.)

There is a dedicated tutor for this course called a "HOOT". He is Iago Braz Mendes. Sessions are Sunday and Tuesday, 5:00 pm to 7:00 pm, starting on 11 February, at Wright Laboratory room 114.

Course web site: http://www.oberlin.edu/physics/dstyer/P111. I will post handouts, problem assignments, and model solutions here.

Topics:

Textbook:

Obtainable from OpenStax. The electronic version is free, but a print version is also available for a relatively modest cost. I will call this book "LSM".

Lectures: In this course I will need to represent many different types of entities on the chalkboard simultaneously. To help keep these different sorts of things straight, I will use various colors. (Some students have found it helpful to take notes with a variety of colored pens.) I will use

the color:    to represent:
white    physical objects
yellow    mathematical lines and surfaces
red    charge and current
blue    electric field
green    magnetic field

Problem assignments: The problem assignments in this course are not a dry appendage designed to keep you indoors on sunny days. Instead, the problems are central to your learning in the course. Problem solving is a more active, and hence more effective, way to learn than reading text or listening to lecture. Problems will be posted on the course web site every Wednesday and are due at the beginning of class the following Wednesday unless there is an exam. My model solutions will be posted at the end of this class, so late assignments cannot usually be accepted. (I may make an exception in the case of a medical or family emergency, but in most cases it is to your advantage to move on to the next assignment rather than to let old work pile up.) In writing your solutions, do not just write down the final answer. Show your reasoning and your intermediate steps. Describe (in words) the thought that went into your work as well as describing (in equations) the mathematical manipulations involved. For numerical results, give units and apply significant figures.

Why do you have to "show your reasoning and your intermediate steps"? Suppose someone claimed "I won reelection in November 2020. I won by a landslide." but could not provide evidence supporting his assertion. Would you belive him? I hope not. Similarly with any scientific (or non-scientific) problem. If you merely present the answer without showing supporting data or reasoning, you have not solved the problem.

The very name "reasoned discourse" means that you present not only your conclusion, but also the reasoning behind that conclusion. If you present only your result, you are not engaged in reasoned discourse.

The problems will come, not from the textbook, but from my "Problems for Physics 111".

You are welcome to consult the library, the Internet, AI resources such as ChatGPT, your friends, or your enemies in working the assigned problems, but the final write-up must be entirely your own: you may not copy word for word or equation for equation. When you do obtain outside help you must acknowledge it. (E.g. "Following the suggestion on page 357 of Elby, The Portable TA to use a cylindrical Gaussian surface, I find that. . ." or "Employing the substitution u = sin(x) (suggested by Carol Hall). . ." or even "In working these problems I benefited from discussions with Mike Fisher and Jim Newton.") Such an acknowledgement will never lower your grade; it is required as a simple matter of intellectual fairness. Each assignment will be graded by a student grader working under my close supervision.

Laboratories: Your laboratory work is an important part of this course, both for its own sake and for the light it sheds on the classroom material. The laboratory is also a good place to question, explore, and generally have fun. Laboratory sections meet for three hours once a week on either Tuesday, Wednesday, or Thursday afternoons starting promptly at 1:30 pm in Wright 214. There will be laboratory-related questions on the exams.

Exams: There will be two in-semester exams and a final. The in-semster exams will be 50 minute exams held at class time on Wednesday 6 March and on Wednesday 24 April; the final exam will be at 9:00 to 11:00 a.m. on Thursday, 16 May (the time set by the registrar). No collaboration is permitted in working the exams. To each exam you may bring an 8.5 by 11 inch page of notes (use both sides), but no other material. (In particular, your lab manual and lab notebook are not permitted.) Calculators are permitted. Before each exam I will distribute a sample exam consisting of exam questions that I have given in previous incarnations of this course. In determining your grade I will drop the lowest hour's worth of exam score (that is, either of the two in-semester exams or half the final, whichever is smaller).

At each exam you're allowed one sheet of paper with your own notes. What are the reasons for this policy?

Guest lectures: The Department of Physics and Astronomy periodically invites visiting scientists to lecture at Oberlin. I will announce these visits in class. If you attend the guest lecture and submit to me a one-paragraph description, you will be awarded 20 extra-credit problem-set points.

The purpose of the guest lectures is to broaden your horizons: to show you physics as it is done today and to present you with a viewpoint different from my own. You will not understand everything that the visiting speakers say . . . neither will I! One objective of the guest lectures is to show you how to get something out of a talk even when you don't understand everything in the talk.

Grading: Your final numerical grade will be compounded of 25% lab, 37.5% problem assignments, and 37.5% exams. In addition, you must receive a passing lab grade to pass this course. On a 40-point scale, those with 40-36 points earn the grade "A", 35-30 points earn the grade "B", 29-20 points earn the grade "C", 19 or fewer points do not pass.

Reserve reading: The following books are on reserve in the Science Library. (They are located on shelves along the south wall, not far to your right when you enter, near some comfortable chairs to encourage browsing.) A text previously used in this course is

These two texts treat the subject matter of this course from a more advanced and/or idiosyncratic point of view: While this one treats these matters from a more elementary and algorithmic point of view: Tensors, cross products, and completely antisymmetric rank-2 tensors: Two books particularly useful for thermodynamics are: You will undoubtedly notice that the problems and exams in this course, or any other physics course, exercise not only your knowledge of physics but also your skills in solving problems. You will find many hints for honing your problem-solving skills in the books And be sure to browse in

Tentative Laboratory, Exam, and Class Schedule

Electricity
Week 1     Lab: Organizational Meeting (brief)
5 February     Introduction
7 February     Electric Charge, Electric Force, and Electric Field
9 February     Visualizing Electric Field: Arrows, Field Lines, and Flux
Week 2     Lab: Electrostatics
12 February     Gauss's Law I
14 February     Gauss's Law II
16 February     Electric Potential
Week 3     Lab: Capacitance
19 February     Conductors in Electrostatic Equilibrium
21 February     Capacitors
23 February     Electric Potential Energy
Week 4     Lab: Mapping Electric Field
26 February     Current: Charge in Motion
28 February     Circuits I: Informal
1 March     Circuits II: Formal
Week 5     Lab: DC Circuits I
4 March     Electrical Safety, Shielding, Grounding
6 March     First Exam
8 March     Discharge of a Capacitor: Physics by Common Sense
Magnetism
Week 6     Lab: DC Circuits II
11 March     Magnetic Forces on Moving Charges
13 March     Magnetic Forces on Currents and
    Magnetic Field Made by a Single Moving Point Charge
15 March     Making Magnetic Field
Electromagnetism
Week 7     Lab: Using an Oscilloscope
18 March     Making the Equations Consistent
20 March     Making E by Changing B
22 March     Implications of Faraday's Law for Circuits
(Spring Break)
Week 8     Lab: Solar Cell
1 April     Uses of Inductors
3 April     Alternating Current Circuits I
5 April     Alternating Current Circuits II
Week 9     Lab: Measuring Magnetic Field
8 April     Solar Eclipse: no class
10 April     Alternating Current Circuits III: LCR circuit
12 April     Something is Missing
Week 10     Lab: AC Circuits I
15 April     Maxwell's Equations and Light
17 April     Electromagnetic Energy and Momentum
19 April     Polarized Light
Thermodynamics
Week 11     Lab: AC Circuits II
22 April     Fluids and Pressure
24 April     Second Exam
26 April     Temperature
Week 12     Lab: Polarization of Light
29 April     Heat and Work
1 May     Heat Capacities; Adiabatic Changes; the Carnot Cycle
3 May     Efficiency of Carnot Engines
Week 13     Lab: Calorimetry
6 May     The Second Law
9 May     Definition of Entropy
10 May     What is Entropy?
Final exam: 9:00 -- 11:00 am, Thursday, 16 May.