Temperature and thermal equilibrium

Hot Cold

Thermometer

Celsius, Fahrenheit, Kelvin

• Andres Celsius (1701-1744). Celsius’ scale relates to the freezing temperature of

water

• 0°C• and the boiling temperature of water

• 100°C

• TF=9/5 32

5

9 CF TT

In mid. continental Russia schools are closed when temperatures reaches -35ºCWhat is the temperature in Fahrenheit's?

Temperature is proportional to the kinetic energy of atoms and molecules: T~KE

Lord Kelvin

• Kelvin’s scale related to the absolute zero – the point

where nothing else can be colder. For the ideal gas, the volume would have reached 0

T (°C)

P (Pa)

-273.15

Conversion of T scales:

15.273 CTT

Thermal expansion

NORMAL SOLIDS

oLL

LINEAR THERMAL EXPANSION OF A SOLID

The length of an object changes when its temperature changes:

TLL o

coefficient of linear expansion

Common Unit for the Coefficient of Linear Expansion: 1CC

1

Example 3 The Buckling of a Sidewalk

A concrete sidewalk is constructed between two buildings on a day when the temperature is 25oC. As the temperature rises to 38oC, the slabs expand, but no space is provided forthermal expansion. Determine the distance y in part (b) of the drawing.

THE BIMETALLIC STRIP

THE EXPANSION OF HOLES

Conceptual Example 5 The Expansion of Holes

The figure shows eight square tiles that are arranged to form a square patternwith a hold in the center. If the tiled are heated, what happens to the size of the hole?

Conceptual Example 7 Expanding Cylinders

Each cylinder is made from a different material. All three have the same temperature and theybarely fit inside each other.

As the cylinders are heated to the same,but higher, temperature, cylinder C fallsoff, while cylinder A becomes tightly wedgedto cylinder B.

Which cylinder is made from which material?

VOLUME THERMAL EXPANSION

The volume of an object changes when its temperature changes:

TVV o

coefficient of volume expansion

Common Unit for the Coefficient of Volume Expansion: 1CC

1

An Automobile Radiator

A small plastic container, called the coolant reservoir, catchesthe radiator fluid that overflows when an automobile enginebecomes hot. The radiator is made of copper and the coolant has an expansion coefficient of 4.0x10-4 (Co)-1. If the radiator is filled to its 15-quart capacitywhen the engine is cold (6oC),how much overflow will spill into the reservoir when the coolant reaches its operating temperature (92oC)?

Why do they tell you to leave a faucet slightly open in the winter up north? .

HEATHEAT

The process by which energy is exchanged between objects because of a difference in their temperatures.

SI: [J] – joules

» James Joule

12.6 Heat and Internal Energy

DEFINITION OF HEAT

Heat is energy that flows from a higher-temperature object to a lower-temperature object because of a difference in temperatures.

SI Unit of Heat: joule (J)

Heat / Energy / Work units

3 types of energy transfer

• Conduction

• Convection

• Radiation

Conduction

• the process whereby energy is transferred directly through a material without any bulk motion of its particles.

• Conduction is mostly common in solids.

• Depending on whether materials conduct heat easily, they are divided into conductors and insulators.

Conduction

k – thermal conductivity

Convection

process in which energy is transferred through a material with any bulk motion of its particles.

Convection is common in fluids

Convection

Radiation• the process in which energy is transferred

by means of electromagnetic waves.