THERMAL PHYSICS Flashcards
Thermal physics is the study of
Temperature, Heat, Internal Energy
o The process by which energy is exchanged
between objects because of temperature
differences is called ____
Heat
____ exists when two objects
are in thermal contact with each other and
there is no net exchange of energy between
them
Thermal Equilibrium
o 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
– Object C could be the thermometer
o Allows a definition of temperature
Zeroth Law of Thermodynamics
o Used to measure the temperature of an object
or a system
o Make use of physical properties that change
with temperature
o Many physical properties can be used
– Volume of a liquid
– Length of a solid
– Pressure of a gas held at constant volume
– Volume of a gas held at constant pressure
– Electric resistance of a conductor
– Color of a very hot object
THERMOMETER
____ can be
defined by the height of
the mercury column
TEMPERATURE
o Thermometers can be calibrated by placing
them in thermal contact with an environment
that remains at constant temperature
– Environment could be mixture of ice and
water in thermal equilibrium
– Also commonly used is water and steam in
thermal equilibrium
Temperature Scale
- ____
o When the pressure of a gas goes to zero, its
temperature is –273.15° C
– This temperature is called absolute zero
o This is the zero point of the ____
– –273.15° C = 0 K
o To convert: TC = T – 273.15
– The size of the degree in the Kelvin scale is
the same as the size of a Celsius degree
Kelvin Scale
defined as 1/273.16 of the temperature of the
triple point of water
Kelvin
Most common temperature scale used in the US
Fahrenheit Scale
____
o Temperature of an ice-water mixture is defined
as 0° C
– This is the ice point or the freezing point of
water
o Temperature of a water-steam mixture is
defined as 100° C
– This is the steam point or the boiling point
of water
o Distance between these points is divided into
100 segments or degrees
Celsius Scale
The ____ of an object is a
consequence of the change in the average
separation between its constituent atoms or
molecules
o At ordinary temperatures, molecules vibrate
with a small amplitude
o As temperature increases, the amplitude
increases
– This causes the object as a whole to expand
Thermal Expansion
o For small changes in temperature
o α, the coefficient of ____, depends
on the material
– See table
– These are average coefficients, they can
vary somewhat with temperature
Linear Expansion
– Use a bimetallic strip
– Two metals expand differently
* Since they have different
coefficients of expansion
Thermostats
Two dimensions expand according to
– γ is the coefficient of ____
Area Expansion
Three dimensions expand
– For liquids, the coefficient of ____ is given in the table
Volume Expansion
– Thermal stresses are smaller than for
ordinary glass
Pyrex Glass
Warming the oceans will increase the
volume of the oceans
Sea Levels
