Thermal Linear Expansion Laboratory

Purposes

Set Up

Due to the limited number of materials, we will be exploring these systems as a class.

linearexp.gif (3099 bytes)

Measurements (include the units!)

Description of object Var Copper pipe Steel pipe PVC pipe
The initial length of the pipe Li __________ __________ __________
The initial temperature of the pipe ti __________ __________ __________
The final temperature of the pipe tf __________ __________ __________
Calculated change in temperature tf - ti __________ __________ __________
The degrees of rotation of the dial q __________° __________° __________°
The diameter of the pin d 0.00065 m 0.00065 m 0.00065 m
Calculated change in length DL __________ __________ __________
Calculated coeficient of linear expansion a __________ __________ __________
Calculated error in a ea __________ __________

Procedure

  1. Take the initial measurements.
  2. Run steam through the pipe.  Lay pipe on paper towels, swathe in paper towels to prevent heat loss.  Set three to four thermometers under the towels on the pipe to monitor the pipe temperature. Recommend that only two of the three pipes above be used: it can take up to an hour for the full pipe length to heat to around 70°C.  Copper and PVC worked well.  Alternative: find a system that delivered more steam than the flask system that was used Spring 2000.
  3. Observe the rotation of the dial
  4. Wait until the full length of the pipe is at the final temperature.
  5. Record the rotation in degrees of the dial.

Calculations

p = 3.141592
DL = (p × d)(q/360°)

The coeficient of linear expansion a can be determined from the formula for linear expansion:
DL = a Li Dt
DL = a Li [tf - ti]
a = DL/(Li[tf - ti])

Use the following table to calculate your percentage error ea:

material a/°C) material a/°C)
aluminum 24 ×10-6 glass, pyrex 3.6 ×10-6
brass 19 ×10-6 iron 12 ×10-6
concrete 12 ×10-6 lead 29 ×10-6
copper 17 ×10-6 quartz 0.5 ×10-6
glass, crown 9 ×10-6 steel 12 ×10-6

Homework

  1. Which material examined in the lab expands the most when heated?
  2. Which material examined in the lab expands the least when heated?
  3. What will the change in length be for a 5.0 meter PVC pipe in Minneapolis, Minnesota between winter and summer if the winter temperature is -15°C and the summer temperature is 30°C?
  4. From the perspective of linear expansivity, why cannot rebar used in concrete be made from a light but strong and corrosion resistant material such as aluminum?
  5. Why is copper pipe preferred by plumbers for connecting sinks to the pipes in the wall?

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