Experiment 3: voltage versus length – PASCO EM-8812 Resistance Apparatus User Manual
Page 17
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T e a c h e r s ’ N o t e s a n d T y p i c a l D a ta
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The following refinements to the experiment setup can be used to improve the data and make the experiment eas-
ier:
•
Increase the sample rate of both sensors (from the default of 10 Hz) to reduce the uncertainty of the slope of
the V versus I graph.
•
Set a stop condition in DataStudio (or on the GLX) to automatically stop data after slightly less than 10 s
(the length of the applied voltage ramp).
•
Set the DC Power supply to automatically stop after a single ramp.
Experiment 3: Voltage versus Length
The graph shows V versus data for the smallest brass wire (A = 0.00203 cm
2
) with I = 1.00 A. The slope equals
ρI/A; thus ρ = 7.46 µΩ·cm. The table below shows ρ determined in this way for all wires.
For the four brass samples, the average value of
ρ is 7.35 µΩ·cm with a standard deviation of about 0.08 µΩ·cm
(1.1%).
A
(cm
2
)
I
(A)
slope =
ρ
Ι
/A
(mV/cm)
ρ
(µΩ·cm)
Brass
0.0127
2.00
1.15
7.28
0.00811
2.00
1.80
7.30
0.00519
1.00
1.42
7.37
0.00203
1.00
3.68
7.46
Copper
0.00811
2.00
0.439
1.78
Aluminum
0.00811
2.00
1.23
4.99
Nichrome
0.00811
0.500
6.63
108
Stainless Steel
0.00811
1.00
9.78
79.3