PLEASE SEE OTHER SIDE

PHYSICS 200 CLASS 1 SPRING 2004 12 January 2004 ASSIGNMENT: Halliday, Resnick, & Walker, Chapter 22; HRW, Chapter 14, sections 1 5 CONCEPTS: 1. four "forces of nature"; how electric force fits in 2. electric charge: one of four "fundamental" quantities; units 3. Coulomb's law. Note similarity to law of gravity. 4. "shell theorems" (pages 296 and 302, and 510, highlighted in green), Note that the text does not prove these theorems. We will do so later on. RECOMMENDED QUESTIONS AND PROBLEMS: Most of the Questions and Problems in Chapter 22 are interesting; do as many as you have time for. In Chapter 22, on-line tutorials are available for Problems 3, 5, 13, 23, 25. See below for instructions. In addition, be sure to work through the sample problems carefully, with pencil and paper. Don t just read them physics is not a spectator sport! Often, the worked examples will show you how to approach the questions and problems at the end of the chapter. ---------------------------------------------------------------- TURN IN: Question 9; Problems 5*, 10*, 13*, 15. Asterisks (*) indicate problems for which on-line tutorials are available. See below for instructions. Be sure your answers are complete. Answers to Questions should be carefully explained- - and problems should be completely worked out. Hints: Question 9 see Fig. 22-4. Problem 13 requires a technique you studied extensively in first semester calculus. 1. I usually try to assign homework problems that encompass a range of difficulty. HRW comes with some nice web-based resources that may be of help both in understanding the physics and solving problems; the link is given on the course web page see my web site, http://employees.csbsju.edu/cgearhart. I hope to experiment with other web-based resources. I will try to assign at least one or two problems each day for which on-line help is available. These problems will be indicated by an asterisk (*). Let me know if you run into any trouble. PLEASE SEE OTHER SIDE

PHYSICS 200 CLASS 2 SPRING 2004 (14 January 2004) ASSIGNMENT: Text, Chapter 23, sections 1 6 CONCEPTS: 1. Induced electric charge; electric dipoles. 2. Electric Field -- Be sure you understand why we introduce this idea. Note that we can equally well speak of a gravitational field this idea may seem a little more intuitively reasonable at first. 3. Lines of force. This concept was introduced by Michael Faraday in the 19th century, and is a marvelous device for "visualizing" electric fields. 4. binomial theorem (calculation on page 526) it is an important and widely used tool for doing approximations 4. Concept of an integral as a device to add up infinitesimal point charges to find the field of an extended object. On-line tutorials: Chapter 23, Problems 13, 21, 23, 31, 39 RECOMMENDED QUESTIONS AND PROBLEMS: Concentrate on the problems for sections 3 5 at the end of Chapter 23 TURN IN: Chapter 23, Question G-23; Problems 10, 11, 13*; Extra Credit, Problem 16 Please note: Questions and problems from the (green) Problem Supplement book have a G in front of them, as in Question G-23 above. 1. Remember that on-line tutorials are available for the starred problems. 2. Remember to follow the guidelines in the course outline for writing up homework. 3. Problem 16 is moderately challenging. In order to approach it, it helps to understand in detail how HRW s calculation with the binomial theorem works, even though that theorem is not absolutely necessary for this problem. Note, for example, that the book skips several steps between Equations 23-5 and 23-6. The book does not expect that you will think those steps are obvious; it does expect you to work through the calculation on your own. I have put a few notes on the binomial theorem on the other side of this page.

2. I have asked you to read in Chapter 14 so that you can see for yourselves the strong analogy between gravitational and electrical forces. For the time being I will assign problems only from Chapter 22. 3. I check my email regularly, including evenings. It's a good way to get through to me quickly far more reliable than voice mail. I will be glad to try to answer questions from the reading and homework assignments via email. 4. Chapter 22 has two purposes. One is obvious to introduce you to static electricity and to Coulomb's law in particular. The other is less obvious to review the mathematics of vectors, and be sure you understand them and know how to work with them. Be sure you keep both purposes in mind!

PHYSICS 200 CLASS 3 SPRING 2004 (16 January 04) ASSIGNMENT: Text, Chapter 23, sections 6 9 CONCEPTS: 1. Concept of an integral as a device to "sum" infinitesimal point charges to find the field of an extended object. Be sure you can work through in detail, understanding every step, the derivations and sample problems in sections 6 7, as well as the calculations in class. 2. I will probably leave sections 8 and 9 pretty much to you. The first makes use of the ideas you studied last semester on constant accelerations and forces. Section 9 is less straightforward one needs to understand that it takes work to rotate an electric dipole in an external electric field; and hence, one can define a potential energy. You may already be familiar with these ideas see Chapter 10, Sections 8 10 for a review. RECOMMENDED QUESTIONS AND PROBLEMS: Concentrate on the problems for sections 6 and 7; but have a look at the ones for 8 and 9 as well. Problem 44 might be a good one to do. On-line tutorials are available for Problems 13, 21, 23, 31, and 39. TURN IN: Chapter 23, Problems 19, 22, 23*,24, 39* 1. This problem assignment is a challenging one. Do not wait until the last moment to start! It may help to work through the derivations and sample problems in the text, as well as your class notes. Hints: For problem 19, you may need to review the simple harmonic oscillator, which you studied last semester. The defining characteristic is that a particle in simple harmonic motion obeys Hooke s law, F = kx, and that the angular frequency ω = k/ m. Note that Eq. 23-6 gives the field along the axis of a charged ring. The result this problem asks you to prove is true only in the limiting case z << R (that is, very close to the ring) in other words, Hooke s law will turn out to be accurate only in that limit. A binomial expansion is not necessary, but will give more insight. Note that problem 22 is another max/min problem. For problems 23 and 24, pick a small chunk of each rod, and treat it as an infinitesimal point charge dq, and calculate the field from that point charge at P using Coulomb's Law; then, develop a scheme for "adding up" all these chunks (that is, integrating) along the rod. 2. Note that the binomial theorem is stated (but not proven) in Appendix E of the text, on page A10. See my handbook as well; and you might want to read further in your n calculus book. Also, test it numerically. For example, is ( 1+ x) 1+ nx numerically correct for a few specific values say, x =.1, n = 4?

PHYSICS 200 CLASS 4 SPRING 2004 (20 January 04) ASSIGNMENT: Text, Chapter 23, sections 7 9 Text, Chapter 24, sections 1 5. We will take two or three days on this chapter, so concentrate on the earlier sections for next time. Work through (don t just read) the worked examples! CONCEPTS: 1. Electric flux. 2. Gauss's Law. Be sure you understand that Gauss's Law is equivalent, both mathematically and physically, to Coulomb's Law. If they are equivalent, why do we need a second formulation? 3. Gauss's Law will permit us to prove a couple of interesting claims: We will be able to prove the two "shell theorems" we introduced in chapter 23. There are other ways of doing these proofs, but this one is the simplest. We will be able to show that if one has a charged conductor (for example, a piece of copper on which we have placed some electric charge), all the charge must reside on the outside surface of the conductor. RECOMMENDED QUESTIONS AND PROBLEMS: In chapter 23, be sure you understand how to do problems involving integration and the binomial theorem. In chapter 24, concentrate on the problems and questions for sections 1 6. Problem 11 is especially interesting it involves very little calculation, but a good deal of thought. TUTORIALS AVAILABLE: Chapter 24, problems 7, 21, 41 TURN IN: Chapter 23, Question 12; Problem 27; Extra Credit: Question 10 Chapter 24, Question 3; Problems 5, 10 1. I have asked you to read section 9 of chapter 23, but am only assigning one extracredit question (for which, as always, I will look for a clear, detailed explanation). We will look at this section again later in the semester, when we talk about magnetic dipoles. For now, be sure you understand why an electric dipole tends to line up with an external electric field. It may help to review the treatment of torque in Chapters 11 13 2. The second lab will meet on days 4, 5 and 6 of cycle 2 (Friday, Monday, and Tuesday, 23, 26, and 27 January). We will do Experiment 2, Electrical Circuits. Bring your lab manual, lab notebook, calculator, and so on with you.

PHYSICS 200 CLASS 5 SPRING 2004 (22 January 04) ASSIGNMENT: HRW, Chapter 24. CONCEPTS: 1. Gauss's law, and why it is equivalent to Coulomb s law. 2. "Gaussian surfaces." As you think about this idea, ask yourself the related question of how one measures the area of an irregularly shaped surface. 3. idea of "electrostatic equilibrium"--charges in equilibrium don't move around 4. The electric field inside a conductor must be zero. Be sure you understand why. 5. In electrostatics, the charge on a conductor must reside entirely on the outside surface. Be sure you can use Gauss s law to explain why. 6. Use Gauss's Law to calculate electric fields for "symmetric" geometries. RECOMMENDED QUESTIONS AND PROBLEMS: Be sure you understand the symmetry arguments used to apply Gauss s law to plane, cylindrical, and spherical geometries, and see if you can do some of the problems for sections 7 9. I will assign more problems along these lines next time. TURN IN: Chapter 24, Question G-25; Problems 7, 9, 15, 19, 25. For the question, remember that G- refers to the green supplementary problem book. As with all questions, be sure to explain your reasoning carefully. 1. The second laboratory meets days 4, 5 and 6, Friday, Monday and Tuesday 23, 26 and 27 January. We will do Experiment 2, Electrical Circuits. 2. First exam: We will spend Monday on Chapter 24, and then move on to Chapter 25. That chapter should take us about three days. This schedule should put the first exam sometime the week of 2 February.

PHYSICS 200 CLASS 6 SPRING 2004 26 January 04 ASSIGNMENT: HRW, Chapter 24 CONCEPTS: 1. Use Gauss s Law to calculate the electric field of problems with planar symmetry 2. Use Gauss s Law to calculate the electric field of problems with spherical and cylindrical symmetry. 3. Proof of shell theorems be sure you understand them RECOMMENDED QUESTIONS AND PROBLEMS: Do as many as you have time for in Chapter 24. Be sure you can do problems involving plane, cylindrical, and spherical symmetry, and that you understand how and why these symmetry arguments work. In addition, work through the Gauss s law simulation on the HRW web site. Be sure you do the self-test exercises. TURN IN: Chapter 24, Question G-30; Problems 26, 28, 29, 46 (part a only); Extra Credit: Problem 41 Note that Question G-30 is related to last Friday s demonstration. As with all Questions, be sure to explain your answer carefully. 1. Remember that the laboratory meets today and tomorrow. 2. The first examination will come after Chapter 25, which we will start on Wednesday. It will take about three days. Possible dates are therefore Thursday, 5 February or Monday, 9 February. The exam will cover Chapters 22 through 25 in HRW, and will consist of questions and problems similar to those at the end of the chapters in HRW. You may bring to the exam one sheet of paper with anything you like written on it except solved problems and worked examples (that is, sample problems ) from the text. Please turn in this sheet of paper with your exam. As part of your preparation for the exam, do lots of problems! Concentrate on the more interesting ones--that is, do not concentrate on the problems that involve no more that plugging numbers into formulas. In addition, have the important laws and results we have derived under good control--be sure you really understand them, so that you are not just reciting laws or equations that you don't quite understand. Be sure you understand and can reproduce derivations of important results and special cases, and the like.

PHYSICS 200 CLASS 7 SPRING 2004 (28 January 04) ASSIGNMENT: HRW, Chapter 8 (review); Chapter 14, section 6; Chapter 25, sections 1 4 Chapter 25 talks about electrical potential energy and the related idea of electric potential. Before going to far in chapter 25, we will review the ideas of potential and kinetic energy and conservation of energy that you studied last semester. CONCEPTS: 1. Potential Energy: Why is potential energy a useful idea? Why do we bother with it? What kinds of potential energies do you know about already? 2. potential energy of a simple harmonic oscillator 3. gravitational potential energy. Note that we have two cases: near the surface of the earth at arbitrary distances from the earth (chapter 14) 4. electric potential; relation between potential and potential energy RECOMMENDED QUESTIONS AND PROBLEMS: Do enough problems from Chapters 8 and 14 to give you a thorough review of potential energy. Tutorials: Chapter 8, Problems 19, 23, 43, 57; Chapter 14, Problems 5, 11, 21, 39, 53; Chapter 25, Problems 17, 22, 37, 43 TURN IN: Chapter 25, Problem 6; Chapter 8, problem 25; Chapter 14, problems 33, 39* 1. Remember that the first exam will come after chapter 25. 2. Hint for chapter 14, problem 39: Assume that the distance from the projectile to the earth will not be approximately constant, so that mgh will not give the potential energy. See if this assumption turns out to be correct. (There is an on-line tutorial for this problem.) PHYSICS 200 CLASS 8 SPRING 2003

PHYSICS 200 CLASS 8 SPRING 2004 (30 January 04) ASSIGNMENT: HRW, Chapter 25 Be sure to work through the sample problems! CONCEPTS: 1. equipotential surfaces; be sure you understand why equipotential surfaces are perpendicular to lines of force, and how to prove it! 2. potential of a point charge; finding the potential of an extended charge distribution by integration of infinitesimal point charges. Note that the integrals are scalars, not vector integrals, and so are often easier. 3. relation between the electric field and the electric potential. Be sure you can calculate the potential from the field (sec. 25.4) and vice versa (sec. 25.9) RECOMMENDED QUESTIONS AND PROBLEMS: Most of the problems in this chapter are interesting do as many as you have time for. ON LINE TUTORIALS FOR: Chapter 25, Problems 17, 22, 37, 43 TURN IN: Chapter 25, Problems 8, 21, 23, 28 and the following Question: Question: Can two different equipotential surfaces intersect? (Hint: This question is related to another one: Can two electric field lines of force intersect? It may be helpful to think about this question in both contexts. 1. The next laboratory will meet, Days 4, 5 and 6, Monday, Tuesday and Wednesday, 2 4 February. We will do Experiment 3, the Oscilloscope. 2. The first examination will be on Monday, 9 February. The exam will cover Chapters 22 through 25 in HRW. The exam will consist of questions and problems similar to those at the end of the chapters in HRW. You may bring to the exam one sheet of paper with anything you like written on it except solved problems and worked examples (that is, sample problems ) from the text. Please turn in this sheet of paper with your exam. As part of your preparation for the exam, do lots of problems! Concentrate on the more interesting ones--that is, do not concentrate on the problems that involve no more that plugging numbers into formulas. In addition, have the important laws and results we have derived under good control--be sure you really understand them, so that you are not just reciting laws or equations that you don't quite understand. Be sure you understand and can reproduce derivations of important results and special cases, and the like. Please see other side

3. Hint on problem 23 Note that you already have the potential of a point charge (derived in class) and the potential for a dipole (Equation 25-30, which I haven't derived, but which I trust all of you will do it would make a good exam question). Since the potentials are scalars, one can just add them. In the coordinate system chosen by the problem, the algebra is simplest if you choose the middle charge as the point charge, and the other two as the dipole. If you make this choice, NOTE THAT THE DEFINITION OF d IS DIFFERENT FROM THAT OF EQ 25-30. You must make the appropriate transformation. One gets the same result if you choose the two bottom charges as the dipole, but the algebra is a little more involved.

PHYSICS 200 CLASS 9 SPRING 2004 3 February 04 ASSIGNMENT: HRW, Chapter 25 CONCEPTS: 1. potential of a point charge; finding the potential of an extended charge distribution by integration of infinitesimal point charges. Since the integrals are scalars, they are often easier to calculate. 2. Potential of a charged conductor or conducting shell 3. Surface charge density (and hence the electric field) is higher in regions where the "radius of curvature" is small. A demonstration and our discussion in class should make this result plausible. See also the discussion in Section 25-10 of HRW. 4. corona discharge demonstration; relation to above 5. Calculate the electric field by taking the derivative of the potential RECOMMENDED QUESTIONS AND PROBLEMS: In preparation for the exam, work as many questions and problems as you have time for in Chapters 22 25. DO BUT DO NOT TURN IN: Chapter 25, Problems 33; and the following questions and problems: Question: If the surface of a charged conductor is an equipotential surface, must the charge be distributed uniformly over the surface? Hint: Recall today s demonstration. Problem: Start from Eq. (25-37), which gives the potential on the axis of a charged disk, and calculate the field. See if your result agrees with the direct calculation of the field that we did in an earlier chapter. Problem: A total charge Q is shared by two metal spheres of radii R 1 and R 2. The two spheres are connected by a conducting wire of length L that is much larger than the two radii. Find (a) the charge on each sphere; and (b) the tension in the R 1 R 2 wire. Explain why we assume L is large L compared to the radii. 1. Remember that the laboratories meet today and tomorrow. 2. Remember that the first exam is scheduled for Monday, 9 February. See the assignment sheet from the last class for details.