PASCO EM-8812 Resistance Apparatus - Manual (Page 15)

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M o d e l N o . E M - 8 8 1 2 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
15
Teachers’ Notes and Typical Data
Experiment 1: Exploratory Study of Resistance
Part A
The relationship between R and is linear,
and the line passes through the origin.
This means that R is proportional to .
Part B
The inverse-square curve fits best. This
means that R is proportional to 1/D
2
, or
that R is proportional to 1/A.
Part C
The table below shows resistivities calculated using data from Part B and the formula .
These data show that the resistivity is about equal (approximately 7.3
µΩ·cm) for all four brass samples.
(cm)
V
(mV)
I
(A)
R
(m
Ω)
24 33.3 0.992 33.6
20 27.7 0.988 28.0
16 22.3 0.990 22.5
12 16.7 0.990 16.9
8 11.1 0.990 11.2
4 5.5 0.991 5.7
D
(cm)
V
(mV)
I
(A)
R
(m
Ω)
0.13 13.7 0.992 13.8
0.10 21.3 0.990 21.5
0.081 33.3 0.992 33.6
0.051 86.9 0.998 87.1
D (cm)
ρ (µΩ·cm)
0.13 7.29
0.10 7.27
0.081 7.26
0.051 7.35
Average: 7.29
ρ
RA
------- =