Temperature Physics 102 Professor Lee Carkner Lecture 1 Things to Know Physics 102: Principles of Physics Professor Lee Carkner Thing you will need Giancoli, “Physics”, 6th edition Scientific calculator Bring both to class Lab manual WebAssign card Help session: TBA (Hopefully Tues, Thurs evenings) Lab section If you need to add a lab or change labs, fill out lab form Labs start this Thursday! How Does the Class Work? Read the book material before class Do the WebAssign homework Before class Download and print out class notes http://helios.augustana.edu/~lc/ph102 Be sure to set as “Pure Black and White” Come to class Do the PAL exercises Answer the Quizdom questions Lab once a week Three tests and final WebAssign Homework will be entered and graded online At webassign.com Click on student login Username is your first and last name together (e.g. “johnsmith”) Institution is “augustana” Password is same as last semester Augustana ID number if new to class After login, click on the current assignment and complete it WARNING: Can only submit it three times Homework Homework will generally be from book Will be posted on webpage if you want to look at them without a computer WebAssign will randomize numbers Available at noon M,W,F Due at midnight Tue, Thu, Sun Cannot turn homework in late or make up Can drop lowest three Each homework worth same amount (100 points) 10% of grade Can drop (or miss) three No make-ups or grade changes PAL What is PAL? Physics Active Learning Each class you will get a PAL worksheet Also will answer questions with Quizdom remotes Worth 15% of your grade Need to come to class Can drop (or skip) three PAL’s Grading on Tests and PALs 1. Written answers must be in complete sentences 2. Numbers must have units 3. Answers must reasonable • If not reasonable, explain why 4. All work must be neat and easily readable Thermodynamics What is thermodynamics? Thermo Dynamics Thermodynamics is the study of thermal and mechanical energy How do you transform one into the other? Where Does Thermodynamics Come From? Back in the early 1800’s people figured out that you can transform thermal into mechanical energy A heat engine Problem: Need to understand what is going on in the engine Temperature How does temperature manifest itself? e.g., the height of a column of fluid We still don’t know what temperature is Thermal Equilibrium A thermoscope Now put the thermoscope in a cup of water They are not transferring heat They are at the same temperature Two bodies at different temperatures placed together will exchange heat until they are in thermal equilibrium (and thus at the same temperature) Zeroth Law of Thermodynamics or if a thermoscope placed near one and then the other reads the same Zeroth Law of Thermodynamics If two objects are each in thermal equilibrium with a third object then they are also in thermal equilibrium with each other Thermometers In order for a thermoscope to be a thermometer it needs to be calibrated Example: the Celsius scale Put it in ice and mark the height of the column as 0 Fill in the numbers 1-99 (in even intervals) in between Only tells you temperature relative to the freezing point of water Types of Thermometers Glass tube Dial Physics: Increase of Physics: Increased bending length with increasing of bi-metal strip with temperature temperature Pros: Pros: Cons: Cons: Radiation Resistance Physics: Change in type Physics: Electrical and amount of radiation resistance increases with emitted with temperature increasing temperature Pros: Pros: Cons: Cons: Temperature Scales Gabriel Daniel Fahrenheit invented the mercury thermometer in 1714 Anders Celsius introduced his scale is 1742 William Thomson, Lord Kelvin, determined from theory that minus 273.15 degrees Celsius is the coldest it can get The Kelvin Scale In science we normally use the Kelvin scale Tells you temperature relative to absolute zero, the coldest anything can get No negative numbers TC = TK -273.15 TF = 9/5 TC +32 A temperature change of 5 Celsius degrees is equal to a temperature change of 9 Fahrenheit degrees Thermal Expansion Heating an object causes it to expand Why? The degree of expansion depends on the change in temperature and the coefficient of expansion We can measure temperature and look up coefficient of expansion Linear Expansion The degree to which the length of an object changes is given by: DL = L a DT Where a is the coefficient of linear expansion This applies to all dimensions of a solid length, width and height Change in length is proportional to length and temperature change If the linear dimensions of a solid change then the volume must change: DV = V b DT Where b=3a Thermal Expansion and Thermometers Consider two strips of metal with different coefficients of linear expansion attached together (bimetal strip) This principle is used in dial thermometers and thermostats Next Time Read: 13.4, 14.3-14.4, 14.6-14.8 Homework: CH 13, P 9, 10, 11, CH 14: 9, 33 Due midnight before class Note that you might have to look up values in the textbook Watch units!
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