PHYSICS 200 CLASS 12 SPRING 2004 (11 February 04) CONCEPTS: 1. Capacitor as a device for storing electric charge

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1 PHYSICS 200 CLASS 12 SPRING 2004 (11 February 04) ASSIGNMENT: HRW, Chapter 26 CONCEPTS: 1. Capacitor as a device for storing electric charge 2. The ability of a capacitor to store charge depends on its geometry and on the "dielectric" used 3. capacitors in series and parallel circuits RECOMMENDED QUESTIONS AND PROBLEMS: Concentrate on the problems for Sections 2 and 3, and on the sample problems. ON-LINE TUTORIALS: Chapter 26, Problems 13, 17, 27, 29, 39 TURN IN: Chapter 26, Problems 7, 9 1. The next exam will come after chapter Recommendation: I suspect many of you would find it helpful to begin keeping a problem notebook, in which you include your worked solutions to the sample problems, and to the problems you are doing in addition to the homework. 3. Remember that the lab meets today and tomorrow. Note the following lab schedule change, as described in my We will spend two weeks on this experiment. Please review carefully the material on graphing and curve fitting in the back of your Physics 191 lab manual.

2 PHYSICS 200 CLASS 13 SPRING 2004 (13 February 04) ASSIGNMENT: HRW, Chapter 26 CONCEPTS: 1. capacitors in series and parallel circuits 2. energy stored in a capacitor 3. Note that the energy stored can be written in terms of either the charge stored on the capacitor, or the electric field. Can one say where the energy "really" is? 4. Effect of a dielectric on capacitance. RECOMMENDED QUESTIONS AND PROBLEMS: Concentrate on the sample problems, questions and problems involving capacitors in series and parallel circuits. NOTE: Textbook authors often draw their circuit diagrams in ways that make it difficult to work out series and parallel combinations. It often helps to think carefully about the textbook diagrams, and then redraw them so that series and parallel combinations are more evident. TURN IN: Chapter 26, Question 5; Problems 13*, 17*, 20. In addition, for Problem 13, assume V = 100 volts and calculate the charge stored on each capacitor.

3 PHYSICS 200 CLASS 14 SPRING 2004 (17 February 04) ASSIGNMENT: Text, Chapters 26, 27 CONCEPTS: 1. energy stored in a capacitor 2. Effect of a dielectric on capacitance. 3. Electric current; note that one can define current independently of the atomic model used by the text. Note also that since we have charge in motion, we can relax our equilibrium result that the electric field is zero inside a conductor. Be sure you understand this point. RECOMMENDED QUESTIONS AND PROBLEMS: Do as many questions and problems as you have time for from Sections 5 and 6 of Chapter 26. TURN IN: Chapter 26, Question G-36; Problems 27*, 29*, 38, Remember that the next exam will come after Chapter 28. I am tentatively scheduling it for Thursday, 11 March. I think we can finish Chapter 28 on 27 February, just before the spring break. When we get back, be can review on Tuesday and have the exam on Thursday. 2. The laboratory will meet on Wednesday, Thursday and Friday of this week. The laboratory will not meet next week (week of 23 February).

4 PHYSICS 200 CLASS 15 SPRING 2004 (19 February 04) ASSIGNMENT: Text, Chapter 27; handout CONCEPTS: 1. Electric current; note that one can define current independently of the atomic model used by the text. Note also that since we have charge in motion, we can relax our equilibrium result that the electric field is zero inside a conductor. Be sure you understand this point. 2. current density 3. Ohm's Law Keep in mind that Ohm s Law is really not a law at all. It is a rule that describes the behavior of a large class of materials, but by no means all. We will see examples in the laboratory of materials that do not obey Ohm s Law. 4. electric energy is dissipated, and appears as heat, when a current goes through a resistance RECOMMENDED QUESTIONS AND PROBLEMS: Most of the problems are interesting. NOTE: Do not forget the green supplementary problem book. There are more worked examples; and in addition, many of the questions are more interesting than the ones in the text. ON-LINE TUTORIALS AVAILABLE FOR: Chapter 27, Problems 11, 19, 25, 35, 37 TURN IN: Chapter 27, Question G-26; Problems 8, 19*, 37*, 42; Extra Credit, Problem 10 (Hint: think about how you handled variable charge density in the context of Gauss s law.) DO BUT DO NOT TURN IN: G-59, G Remember that problems and questions prefaced with G are in the green supplementary problem book. Answers to odd-numbered problems are in the back. 2. I hope to spend only one day on this chapter. Don't let yourself get behind. 3. The essay on "Exponential Growth" is very important. I will probably not spend much time on it in class, but you should read it carefully it is material you will use many times in any area of science or engineering. At some point, I will ask you to turn in problem 2 on page 803. We will also use these ideas in chapter 28.

5 PHYSICS 200 CLASS 16 SPRING February 04 ASSIGNMENT: Text, Chapter 28 CONCEPTS: 1. emf as a "charge pump" that maintains a potential difference in a circuit. Read carefully the qualitative discussion on pages Kirchoff's Laws (or rules) for simple DC circuits--there are two of them 3. resistances in series 4. resistances in parallel RECOMMENDED QUESTIONS AND PROBLEMS: Concentrate on the questions, problems, and sample problems through Section 6. ON-LINE TUTORIALS AVAILABLE FOR: Chapter 28 7, 13, 33, 37, 47 TURN IN: Chapter 28, Question G-27; Problems 12, 13*, 17, G The second exam will be on Thursday, 11 March, and will cover chapters First-year students: Before you register for next fall's classes, be sure you find an advisor in your major department, and talk over your program with him/her, well before you register. For physics and most pre-engineering majors, your advisor should be in the Physics Department. (Students interested in chemical engineering should find an advisor in the Chemistry Department.) Any of us in the Physics Department would be happy to act as an advisor just ask! 3. The laboratory will not meet this cycle (26-27 February and 8 March). In the following cycle (12/15/16) March, we will do Experiment 5, RC Circuits.

6 PHYSICS 200 CLASS 17 SPRING 2004 (25 February 04) ASSIGNMENT: HRW, Chapter 28; "Exponential Growth " handout CONCEPTS: 1. voltmeters and ammeters 2. RC Circuits--be sure you review exponential functions and logarithms carefully. RECOMMENDED QUESTIONS AND PROBLEMS: Concentrate on the Questions and Problems for Sections 7 and 8. Problems 45 (Chapter 27), and its continuation, Problem 56 (Chapter 28) are also interesting. Remember that the simulations on the HRW web site are another good source for problems involving multi-loop circuits. Be sure that you understand how to solve this class of problems! TURN IN: Chapter 28, Question G-34; Problems, 31, 51, 52; "Exponential Growth" handout, problem 2 DO BUT DO NOT TURN IN: Question G-37; Problems 36, G The next exam will be on Thursday, 11 March. The exam will cover Chapters 26 through 28 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. The exam will consist of questions and problems similar to those at the end of the chapters in HRW. It often helps to give yourself a sample exam: Pick a problem from HRW (or from the green supplemental problem book) and see if you can do it under test conditions that is, in 10 or 15 minutes.

7 PHYSICS 200 CLASS 18 SPRING 2004 (27 February 04) ASSIGNMENT: Text, Chapter 28; "Exponential Growth" handout CONCEPTS: 1. RC Circuits 2. exponential functions RECOMMENDED QUESTIONS AND PROBLEMS: In Chapter 28, be sure you have worked through all of the sample problems, and then try to do as many more as you have time for. Be sure you understand how to use Kirchhoff s laws to analyze the voltages and currents in a circuit. DO BUT DO NOT TURN IN: Chapter 28, Problems 37*, 43, 52, The second exam will be on Thursday, 11 March, and will cover Chapters 26 through 28. You may bring to the exam one sheet of paper with anything you like written on it except solved problems and worked examples from the text. The exam will consist of questions and problems similar to those at the end of the chapters in HRW, and in the supplementary problem book. 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 than plugging numbers into formulas. And try to do some problems under test conditions that is, pick a problem you have not done and try to do it in 10 minutes or so.