Temperature

Physics 102Professor Lee

CarknerLecture 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 units3. 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

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:

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 -273.15TF = 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:L = L T

Where 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:

V = V T Where =3

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!