Temperature

1. Temperature Physics 102 Professor Lee Carkner Lecture 1

2. 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!

3. 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

4. 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

5. 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

6. 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

7. Grading on Tests and PALs • Written answers must be in complete sentences • Numbers must have units • Answers must reasonable • If not reasonable, explain why • All work must be neat and easily readable

8. Thermodynamics • What is thermodynamics? • Thermo • Dynamics • Thermodynamics is the study of thermal and mechanical energy • How do you transform one into the other?

9. 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

10. Temperature • How does temperature manifest itself? • e.g., the height of a column of fluid • We still don’t know what temperature is

11. 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)

12. 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

13. 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

14. Glass tube Physics: Increase of length with increasing temperature Pros: Cons: Resistance Physics: Electrical resistance increases with increasing temperature Pros: Cons: Dial Physics: Increased bending of bi-metal strip with temperature Pros: Cons: Radiation Physics: Change in type and amount of radiation emitted with temperature Pros: Cons: Types of Thermometers

15. 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

16. 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

17. 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

18. Linear Expansion • The degree to which the length of an object changes is given by: DL = L aDT • 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 bDT • Where b=3a

19. 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

20. 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!