Physics 2025 Lab 11: Thermal Expansion
Purpose of this Minilab
• Learn about and determine the coefficient of thermal
expansion.
• Determine the lowest possible temperature (absolute
zero).
Physics 2025 Lab 11: Thermal Expansion
Thermal Expansion in one Dimension (Length
Change)
 L  Lo  T
change in length
change in temperature
initial length
coefficient of thermal expansion (depends on the material)
Physics 2025 Lab 11: Thermal Expansion
Thermal Expansion Apparatus
length gauge
Thermistor
(resistance depends on temperature)
3 different
metal tubes
Physics 2025 Lab 11: Thermal Expansion
Inserting the Metal Tube
Angle
bracket
Gauge
pin
Attach thermistor.
Tighten screw.
Insert metal pin
as shown.
Tighten screw.
Physics 2025 Lab 11: Thermal Expansion
Cover Thermistor with Insulation, Attach
DMM.
Physics 2025 Lab 11: Thermal Expansion
Thermistor
•Thermistor has resistance that changes with temperature.
•Conversion scale is on the thermal expansion apparatus.
•You need to interpolate to get temperature for values in between
those that are listed.
•Interpolation procedure is shown in manual.
Physics 2025 Lab 11: Thermal Expansion
Steam Generator ( Change Temperature of Metal
Rod)
Rubber hose goes to metal
rod.
Remove
plug and
fill in
sufficient
amount
of
water.
Second
outlet
should
be
plugged.
Dial lets you change the amount of
steam generated.
Physics 2025 Lab 11: Thermal Expansion
Steam from
steam
generator
Put small cup here
to catch condensed
water.
Lift this end up so that condensed water
runs out the other end of the metal rod.
Physics 2025 Lab 11: Thermal Expansion
Measurement
• Set gauge to “zero” at room temperature.
• Start steam generator.
• Watch resistance (to monitor temperature) and length
expansion.
• Record highest temperature (lowest resistance) measured.
• Record maximum expansion measured.
• Calculate the coefficient of thermal expansion.
Note: Due to time delays relating to thermal conduction the
highest temperature and the largest expansion may not happen
exactly at the same time.
Physics 2025 Lab 11: Thermal Expansion
Absolute Zero Temperature
For ideal gases (gases at low pressure)
PV  n R T
Pressure
Temperature
(in degrees Kelvin)
Volume
Universal gas constant
Amount of gas in moles
Physics 2025 Lab 11: Thermal Expansion
Absolute Zero Temperature
PV  n R T
The ideal gas law implies:
As the gas is cooled more and more, the pressure sinks
(if the volume of gas and the amount of gas is kept constant).
 For P = 0 the lowest possible temperature is reached.
Physics 2025 Lab 11: Thermal Expansion
Estimating Absolut Zero Temperature
1) Keep volume of gas constant.
2) Keep amount of gas constant.
3) The P versus T graph is a straight line with slope nR/V.
P
nR
P
T
V
0
T
Measuring at least
4) Plot T in degrees Celsius.
5) Determine lowest possible T in Celsius. two points lets
6) Determine the uncertainty in lowest T. you extrapolate to
P=0.
Physics 2025 Lab 11: Thermal Expansion
Determining the Pressure of the Gas Inside the Sphere
Gauge Pressure = Pressure inside the sphere – Pressure outside the sphere
Read gauge
Measure with barometer
Varying the Temperature of the Gas in the Sphere
Dip the sphere into boiling water (to get approx. 100 Celcius).
Dip the sphere into ice water (to get approximately 0 Celcius).
Use the same sphere at different temperatures.
(the amount of gas in different spheres may not be the same).
Physics 2025 Lab 11: Thermal Expansion
Estimating the Uncertainty in Lowest T
P
0
T
Possible range of lowest
temperature.