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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”, 6 th edition Scientific calculator Bring both to class Lab manual WebAssign card Help session:

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Temperature l.jpg
Temperature

Physics 102

Professor Lee Carkner

Lecture 1


Things to know l.jpg
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!


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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


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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


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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


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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


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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


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Thermodynamics

  • What is thermodynamics?

    • Thermo

    • Dynamics

  • Thermodynamics is the study of thermal and mechanical energy

    • How do you transform one into the other?


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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


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Temperature

  • How does temperature manifest itself?

    • e.g., the height of a column of fluid

    • We still don’t know what temperature is


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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 l.jpg
    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


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    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 l.jpg

    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


    Temperature scales l.jpg
    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


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    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


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    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


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    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


    Thermal expansion and thermometers l.jpg
    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


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    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!