1. Welcome to Physics 7A! Winter 2011 Prof. Robin D. Erbacher 343 Phy/Geo Bldg erbacher@physics.ucdavis.edu Prof. Robin D. Erbacher 343 Phy/Geo Bldg erbacher@physics.ucdavis.edu

2. Physics 7A -A/B This course has two instructors:  Prof. Robin Erbacher (me) rderbacher @ucdavis  Prof. Hsin-Chia Cheng (Lead DL Instructor) hcheng @ucdavis You are enrolled in Physics 7A-A/B, lectures Mondays.  7A-C/D is offered this quarter as well but has different meeting times. Final exam is Saturday March 19 th, 10:30 am-12:30 pm  If you know you cannot make the final, you should take 7A in a different quarter. There are *no* make-up exams. This course has two instructors:  Prof. Robin Erbacher (me) rderbacher @ucdavis  Prof. Hsin-Chia Cheng (Lead DL Instructor) hcheng @ucdavis You are enrolled in Physics 7A-A/B, lectures Mondays.  7A-C/D is offered this quarter as well but has different meeting times. Final exam is Saturday March 19 th, 10:30 am-12:30 pm  If you know you cannot make the final, you should take 7A in a different quarter. There are *no* make-up exams.

3. Course Website and Policy Our website will be centered around Smartsite. Please read the course policy as soon as possible and let us know if you have questions.

4. Academic Dishonesty Cheating of any sort is not tolerated. This includes but is not limited to: Copying during quizzes/exams. Taking a test for another student. Having a friend use your clicker to register you as present when you are not. Modifying a quiz before asking for a re-grade. As soon as dishonesty is suspected the student is referred to Student Judicial Affairs.

5. Personal Response System A.K.A - Clickers! We will use these to allow you (and us) to gauge your understanding on conceptual questions during lecture. You will receive credit for participation by answering questions. No matter whether correct or wrong. You need your own with your own student ID (bookstore). Bring clicker to next lecture!

6. QuizzesQuizzes We will have 5 quizzes during lectures, on alternate weeks. You must attend your assigned lecture time: sleeping is not an excuse to go to a different lecture. Your first quiz will be next week, Monday Jan 10th. Bring a calculator -- you may need it and we don’t have any to lend. QRST Green circles help identify you (name, ID). Purple circles helps them enter results accurately. We use letter “rubric” codes for partial credit scoring.

7. Grading Policy The full course policy is in the document linked on Smartsite under Resources. You must read this! Quizzes: The lowest of your 5 quiz scores will be dropped for the final quiz average. There are no make- up quizzes. If you miss one, that one will be dropped. Final Grade Determination Your final grade is calculated two ways: 5% PRS + 45% top 4 quiz avg + 50% final exam +/- DL OR 5% PRS + 20% top 4 quiz avg + 75% final exam +/- DL The most favorable score is used for your grade.

8. Your First DL… Discussion Labs (DLs) begin immediately after lecture today with section 1. All DLs are in EPhSci 2319. Equipment tables are set up there. People who are wait-listed or not enrolled in the DL need to obtain a PTA number from their TA: In DL : Don’t join a table immediately. Collect in a corner while the TA begins business, Then the TA will address enrollment issues. Full sections will give PTA numbers at the 2 nd meeting. Important

9. Who Am I? I’m an Associate Professor of Physics (tenured) here at Davis. My research is in elementary particle physics. I’m from Pacifica, CA (well, Los Angeles originally) I went to U.C. San Diego for undergraduate, majoring in physics, with minors in Lit/Writing and Poly Sci. I went to graduate school at Stanford University. PhD thesis at SLAC (Stanford Linear Accelerator Center). “Precision Measurement of the Spin Structure of the Proton ” Postdoctoral Research Associate at Fermilab (Fermi National Accelerator Lab) in Chicago suburbs. Professor: UC Davis Physics department.

10. Particle Physics Research protons anti-protons + Fermilab (Tevatron): (Fermi National Accelerator Lab), near Chicago. CERN (LHC): (Conseil européen pour la Recherche Nucléaire) Fermilab

11. What is Physics? We begin with the child-like wonder about our everyday world. Why is the sky blue? Is there anything colder than ice? How does a light switch work? How do magnets work? How do planes fly? Why does scuffing your feet on carpet “zap” you? Why can some people play pool with great precision?

12. Physics: Find Common Models to Explain Many Phenomena Some of these models use the same principles: Depends on the question asked!

13. QuestionQuestion How do we know that M Earth = 5.98 x 10 24 kg? “Look it up in a book” misses the point. Treat the Earth, planets, and the sun as systems that obey the same principles (or models) as mundane objects such as apples and blocks.

14. Models of the Universe Using similar principles and models we can measure the mass of stars and galaxies: We know how much stars weigh (roughly). We know how much light stars give off (roughly). … So we can “count” the stars and figure out how much of the mass is “stuff we know”. But “stuff we know” is only ~<3% of the mass of the galaxy! Lots of discoveries to make!

15. Physicists…Physicists… Wonder about the world around them. Try to explain phenomena using a few principles (models). We cannot “pick and choose” when an explanation works What is the world made of? What holds the world together? Where did we come from? While our models may not always hold true, we have some understanding of when they’re valid. Physics is taking this approach in the physical world!

16. What is Physics 7? Physics 7 is a 3-quarter series of physics classes, typically taken by bio-science and other non-physical science majors. Physics 7A: Energy conservation, thermodynamics, particle models of matter. Physics 7B: Classical Mechanics, rotational motion, fluids, circuits. Physics 7C: Wave phenomena, optics, electricity and magnetism, the atom and modern quantum mechanics.

17. What is Physics 7, really? Physics 7 is a new approach to teaching and learning introductory physics. It involves: Learning by doing. Active learning. Application of models to various physical systems. Learning by exploration in a small group. Using a chalkboard and discussing openly.

18. What is Physics 7? It will require your active participation! Your DL grade will reflect this. Models… Discussion /Lab Lecture Quiz & Final Text

19. The Physics 7 Approach Active learning is key to “getting” the concepts in Physics 7 and being able to apply them to new situations. Most of your learning will take place in the Discussion Labs (DLs), so attendance is mandatory. The lecture will provide a framework (and in some cases a review) for the subject material, and will allow more explanation and demonstration of concepts. Your DL instructor will only give you guidance and pointers about the right way of thinking-- they will not in general solve the problems for you! To solve the problems, interact strongly with your small student group (5-6 people) and the DL section (the whole class: ~30 people).

20. A Slightly Different Philosophy We do not emphasize getting the right answer, though that is important too. In DLs, FNTs (For Next Times), quizzes, and the final, we are looking for indications that: 1) The problem is clear to you. 2) You are arriving logically to the next step. 3) You clearly understand which model to apply to the problem at hand, why, and how to do it.

21. Physics 7A Strategy Learn to think logically and to make valid arguments when describing a system or solving a problem. Learn to apply analytical principles and logic to understand problems and devise solutions. Learn to reason with models and explain the world around us. We are not here to memorize equations or rote procedures in problem-solving.

22. Models

23. The Bohr Model of the Atom “The atom is nothing but a little electron orbiting around a proton.”

24. Examples of Models Models in Physics: Newtonian mechanics Standard Model of particle physics Standard Model of cosmology Models in Biology: Protein-lipid interaction model Protein-protein interaction model (Don’t ask me about these last two!)

25. Models in Physics 7A Three-phase model of matter Energy-interaction model Mass-spring oscillator Particle model of matter  Particle model of bond energy  Particle model of thermal energy Thermodynamics Ideal gas model Statistical model of thermodynamics We start with These two…

26. Intro: Three Phase Model

27. Three Phase Model of Matter The basic idea

28. Graph of Ice to Steam Stage A: This is the very cold ice starting to warm up Here, it goes from -30 to 0. It is all still ice. Energy is added, but no phase change.

29. Graph of Ice to Steam Stage B: Ice is now at zero degrees and heat (energy) is still being added. As energy is added, the temperature is constant and stays at zero until all ice is gone. Solid/liquid co-exist. All the energy went into melting the ice, not changing temperature.

30. Graph of Ice to Steam Stage C: It is now all water and heat (energy) is still being added. The heat goes into raising the temperature of the water. No phase change.

31. Graph of Ice to Steam Stage D: The water is now at the boiling point (100 deg) and heat is still being added. The energy goes into changing the water into steam. No temperature change. This is another mixed phase. Liquid/Gas co-exist.

32. Graph of Ice to Steam Stage E: All of the water has now turned into steam. As heat is added, the temperature increases. No energy goes into changing phase, all into making the pure substance hotter.

33. Intro: Energy Interaction Model

34. Energy Systems E therma l E bond E movement (KE) E gravit y E electri c E sprin g There are many different types of energies called energy systems:........ For each energy system, there is an indicator that tells us how that energy system can change: E thermal : indicator is temperature E bond : indicator is the (mass of) initial and final phases

35. Energy Interaction Diagrams - Closed System EaEa EbEb EcEc Conservation of Energy The total energy of a closed physical system must remain constant. So, the change of the energies of all energy systems associated with the physical system must sum to zero. Change in closed system energy = ∆E a + ∆ E b + ∆ E c = 0

36. Energy Interaction Diagrams - Open System EaEa EbEb EcEc Conservation of Energy The change of the energies of all systems associated with an open physical system must sum to the net energy added or removed. Energy is added or removed as Heat (Q) or Work (W). Change in open system energy = ∆E a + ∆ E b + ∆ E c = (Energy added) - (Energy removed) = Q + W. Energy addedEnergy removed

37. Energy Interaction Diagrams Example: Melting Ice T i = 0°C  T f = room temperature Temperature Energy of substance solid liquid gas l-g coexist s-l coexist Initial T MP T BP Final

38. Energy Interaction Diagrams Example: Melting Ice Process 1: Ice at T=0ºC  Water at T=0ºC Process 2: Water at T=0ºC  Water at room temperature Temperature Energy of substance solid liquid gas l-g coexist s-l coexist Process 1 Initial T MP T BP Process 1 Final / Process 2 Initial Process 2 Final

39. Energy Interaction Diagrams Example: Melting Ice Process 1: Ice at T=0ºC  Water at T=0ºC Ice Initial phase Solid, Final phase Liquid E therm al E bond

40. Energy Interaction Diagrams Example: Melting Ice Process 1: Ice at T=0ºC  Water at T=0ºC Ice ∆T=0 ∆E th =0 Initial phase Solid, Final phase Liquid E therm al E bond Heat

41. Energy Interaction Diagrams Example: Melting Ice Process 1: Ice at T=0ºC  Water at T=0ºC Ice ∆T=0 ∆E th =0 Initial phase Solid, Final phase Liquid ∆E th + ∆E bond = Q+W ∆E bond = Q E therm al E bond Heat m water

42. Energy Interaction Diagrams Ice E therm al E bond Example: Melting Ice Process 2: Water at T=0ºC  Water at room temperature Initial phase Liquid, Final phase Liquid

43. Energy Interaction Diagrams Ice E therm al E bond Example: Melting Ice Process 2: Water at T=0ºC  Water at room temperature Initial phase Liquid, Final phase Liquid ∆E bond = 0 T ∆E th + ∆E bond = Q+W ∆E th = Q Heat

44. Thermal Equilibrium and Heat

45. Heat Transfer An ice-cube at 0 o C sits in a bath of water at 0 o C. Water and ice can exchange heat with each other but not with the environment. What is the direction of heat transfer? A. From ice-cube to water B. From water to ice-cube C. Neither of above D. Impossible to tell 0 0 C Water Ice-cube 0 0 C

46. Thermal Heat Starting definition of heat (to be revised much later): Heat (Q) is the transfer of energy from a hot object to a cold object because the objects are at different temps. Energy leaves hot objects in the form of heat. Energy enters cold objects in the form of heat. Corollary: If the two objects are at the same temperature, no Q (heat) flows between them. Low temp High temp Q

47. Thermal Equilibrium If the two objects are at the same temperature, no heat flows between them. in thermal equilibrium A system in thermal equilibrium is a system whose temperature is not changing in time. T final Energy leaves hot objects in the form of heat Energy enters cold objects in the form of heat Low tempHigh temp

48. EquilibriumEquilibrium The Zeroth law of thermodynamics says: Since they are in thermal equilibrium with each other, there is no net energy exchanged among them. If objects A and B are separately in thermal equilibrium with a third object C, then A and B are in thermal equilibrium with each other If objects A and B are separately in thermal equilibrium with a third object C, then A and B are in thermal equilibrium with each other

49. EquilibriumEquilibrium The Zeroth law of thermodynamics example: Let the third object C be the thermometer. If the two readings are the same, then A and B are also in thermal equilibrium. Energy (heat) will not flow between A and B if put together.

50. Reaching Thermal Equilibrium A cup of hot coffee left in a room… A thermometer Cold beer It can take some time for things to reach thermal equilibrium with its environment. ~ what is happening at microscopic level? => more to come when we cover Particle models of thermal energy

51. Slowing things down… C = [C] = J/K Coffee cup: ceramic material A thermometer Tip: metal Body: glass, plastic Beer glass: glass Heat capacity [C] of substances: A measure of the amount of energy required to increase the temperature of the substance a certain amount

52. Heat Capacity Heat capacity C is an extensive property: 2kg of water will have twice the heat capacity of 1kg water Heat capacity of substances: A measure of the amount of energy required to increase the temperature of the substance a certain amount C = [C] = J/K

53. Specific Heat Capacity Porcelain 1.1kJ/kgK Tip:metal (Silver: 0.24kJ/kgK) Body: plastic ~ 1.2kJ/kgK Glass 0.84kJ/kgK Specific heat capacity C p is an intensive property: Specific heat capacity only depends on the substance Specific heat capacity C p of substances: the amount of energy per unit mass/unit mole required to increase the temperature of the substance by one degree Kelvin [C p ] = kJ/kgK = kJ/moleK

54. An Aside on “calories” The scientific "calorie" is spelled with a lower-case "c". One "calorie" = 4.184 Joules The "dieter's" calorie is spelled with an upper-case "C". One "Calorie" = 1000 calories

55. Next Time: Energy Conservation, more on Equilibrium, Heat Capacity, Specific Heat, More Energy Interaction Diagrams

56. Reminder…Reminder… Next lecture contains a quiz. Bring your calculator. Bring your Clicker for participation credit.

57. Background Information:

58. A Model: Definitions Models can help us organize our thinking, can contain other models, and can be very useful. Models also have limitations: experiment is the final judge.

59. Three Phase Model- Definitions Pure substances: one chemical substance -water vs. unpasteurized apple cider Phases: solid, liquid, and gas Temperature: measure of the hotness of something Energy: here, it is something that is transferred in the form of heat or work Phase change temperature: the unique temperature at which a pure substance changes from one phase to another

60. Conservation of Energy Energy is both a thing (quantity) and a process. You & I contain energy, as do the chairs you sit on and the air we breathe. We cannot see it, but we can measure the transformation of energy (or change,  E). Conservation of Energy Energy cannot be created nor destroyed, simply converted from one form to another. If the energy of an object increases, something else must have given that object its energy. If it decreases, it has given its energy to something else. Energy transfer is done through Heat or Work. NOTE: The total energy of a closed system remains constant! This course is about energy, how its transferred, how its conserved.