Chapter 10 Thermal Physics 1. Temperature and the zeroth Law of Thermodynamics 2. Thermometers and...

Chapter 10

Thermal Physics1. Temperature and the zeroth Law

of Thermodynamics2. Thermometers and Temperature

Scales3. Thermal Expansion

Thermal Physics What is Thermal Physics? What is Heat? What is Thermal Contact? What is Thermal Equilibrium?

Zeroth Law of Thermodynamics

If objects A and B are separately in thermal equilibrium with a third object, C, then A and B are in thermal equilibrium with each other.

Allows a definition of temperature

Thermometers What is a thermometer? A Mercury thermometer Gas thermometer

Temperature Scales How does one

define a temperature Scale?

The Celsius scale The Fahrenheit

scale The Kelvin scale

Kelvin Scale Why do we

need this scale?

What is first point?

What is triple point?

Some KelvinTemperatures Some

representative Kelvin temperatures

Note, this scale is logarithmic

Absolute zero has never been reached

Converting Among Temperature Scales

273.15

932

55

329

95

C K

F C

C F

F C

T T

T T

T T

T T

Converting Among Temperature Scales –Example

1. A pan of water is heated from 25 °C to 80 °C. What is the change in temperature on the Kelvin scale and on the Fahrenheit scale?

Thermal Expansion What is thermal expansion? Linear Expansion Area expansion Volume expansion

Applications of Thermal Expansion – Bimetallic Strip

Thermostats Use a bimetallic strip Two metals expand differently

Since they have different coefficients of expansion

Thermal Expansion – Example

1. A steel railroad track has a length of 30.00 m when the temperature is 0°C. What is its length on a hot day when the temperature is 40°C?

Thermal Expansion – Example

1. A hole of cross-sectional area 100.00 cm2 is cut in a piece of steel at 20°C. What is the area of the hole if the steel is heated from 20°C to 100°C?

Unusual Behavior of Water