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M o d e l N o . T D - 8 5 1 3
E x p e r im e n t # 2 : An g s t r o m ’s M e t h o d
11
A. Aluminum
Set-up
1.
In DataStudio set the sampling rate of the Temperature Array to 2 Hz. Create a
graph to display temperatures measured by both thermistors in the aluminum bar
(T5 and T6).
2.
Set the power supply to output an 8 V positive triangle wave with a 30 s period,
as shown in the diagram. See the PI-9877 DC Power Supply manual for detailed
instructions.
Procedure
1.
Start recording data. While driving the apparatus with the triangle wave, monitor
the temperature waves until each has stabilized with constant amplitude. Stop
recording and delete the data run. (Let the power supply continue to run.)
2.
Start recording data. After two complete cycles of the driving wave, stop record-
ing.
3.
On the graph, measure the amplitudes of both waves (A
c
and A
f
) and the time dif-
ference between corresponding peaks of the two waves (
∆
t). Make a copy of the
table below and record these measurements in it.
4.
Repeat steps 2 and 3 for a total of three data runs and record all values in your
table.
5.
On the power supply, set the period of the triangle wave to 40 s and repeat steps 1
through 4.
You can start the following analysis while you wait for the system to stabilize.
6.
Set the period of the wave to 50 s and repeat steps 1 through 4 again.
Analysis
1.
For each of the data runs recorded with a 30-second triangle wave, calculate the
thermal conductivity (k). What is the average value of k? What is the uncertainty
of the average?
8 V
0 V
30 s
Power Supply Settings:
Max. Voltage
8 V
Min. Voltage
0 V
Period
30 s
Auto-repeat
−
0
Period (s)
A
c
A
f
∆
t
k
(W/m·K)
Average
k
(W/m·K)
30
40
50
Average
