Resistance and the Length of Wire
Purpose: In this experiment, a relationship between the resistance of current flow in a wire versus the length of the
wire will be investigated. The electrical property of the material the wire is made of will also be explored.
Materials:
-
wire on meter stick
a multi-meter set to 200 
Procedure:
1. Make sure that your multi-meter dial is turned to 200 Ω toward the right side. The screen will read OL.
2.
Place one probe of the multi-meter at the end zero position on the meter stick and the other at 10 cm.
3.
Read and record the multi-meter in a data table. The meter reading will change and it may take some time
to before the value stops. Wait until a value stays for about 5 seconds before recording.
4.
Repeat the measurements with the probes 20, 30, 40, etc. cm apart and record.
5.
Turn OFF the multi-meter by turning the dial straight up to O.
Length of wire (cm)
Resistance (Ω)
10
20
30
40
50
60
70
80
90
100
6.
Graph your data of resistance () v. length of wire (cm). Draw a “line of best fit”, bisecting your data
points.
7.
Find two new points on your line of best fit and label them. In a corner of your graph paper, calculate the
slope of this best fit line.
Questions and Analysis
1.
What relationship can be found from your graph? Write a sentence that uses both x-axis and y-axis
variables and the relationship correctly.
The formula for the resistance of a conductor is given by
R
l
A
Where R represents _____________________ measured in __________
Where l represents _____________________ measured in _________
Where A represents _____________________ measured in __________

Where  represents _____________________ measured in __________
2.
3.
Now look carefully at the formula. Which variables are constant? These variables combine to form the
slope of your graph. Write these two variables in fraction form and set them equal to your calculated slope.
From your equation in question 2, calculate the experimental resistivity (exp) of the wire material.
4.
The gauge number of a wire is a reference to its thickness; the larger the number, the thinner the wire. The
gauge number of the wire is given, use the attached gauge table to find the cross-sectional area of your wire
and record both.
5.
From the attached gauge table, determine the type of conductor the wire was made from and calculate the
% error. Use your experimental value (exp)and the accepted value (acc)from the table.
% error =
Experimental - Accepted
Accepted
6.
Name and explain four factors that can change resistance.
x 100
Resistivity Table
Temperature = 20˚ C
R
Material
Silver
Copper
Gold

Aluminum
Tungsten
Nickel
Platinum
Nickelsilver
Nichrome
Carbon
Silicon
Glass
Rubber
l
A
 = Resistivity (Ω cm)
1.59 X 10 –6
1.72 X 10 –6
2.44 X 10 –6
2.82 X 10 –6
5.6 X 10 –6
7.8 X 10 –6
11.0 X 10 –6
4.9 X 10 –5
11.5 X 10 –5
3.5 x 10 -3
640 X 10 2
1.0 X 10 12
1.0 X 10 15
Gauge Number Table
Gauge Number
000
00
8
12
14
16
18
20
22
24
28
30
“the thickness of a wire”
Diameter (cm)
Cross Section (cm2)
1.040
0.8503
0.9266
0.6743
0.3264
0.08366
0.2053
0.03309
0.1628
0.02081
0.1291
0.01309
0.1024
0.008231
0.08118
0.005176
0.06438
0.003255
0.05106
0.002047
0.03969
0.001237
0.03175
0.0007917
Formal Lab Report
Formal lab reports will be occasionally assigned and will be worth 50 points. They should be
typed, and have a cover page (consisting of a title, “physics”, your name, and the due date,
centered on the first page). They should be in the following format:
Purpose: (“To find the relationship between . . .”, etc.) This is the point of why the
experiment is being conducted, usually referencing a problem.
Hypothesis: A hypothesis is often referred to as an “educated guess,” which is a prediction that
will be tested in the experiment. Not all labs will have a hypothesis. Record a hypothesis before
starting the experiment. A hypothesis that is subsequently disproved does not make the
hypothesis a failure; there is no need to change the original (previously untested) hypothesis.
Materials: A list of the materials required.
Procedure: A step-by-step description of the experiment, clearly stated.
Data: These are the results of the experiment, presented in one or more of the following
formats: tables, graphs, or drawings (the form the data takes is dependent on the experiment).
Include sample calculations.
Questions: Record and answer any questions in the lab.
Conclusion: The conclusion should make reference to the problem in the purpose, hypothesis,
procedure (especially in terms of the validity of the data), and the data. All conclusions should
be driven by the data. It is essential that the student discuss any factors that may have affected
the validity of the data, error analysis, and (depending upon the lab) describe how to improve the
lab.
Typing symbols: if you type the following letters, highlight the target, and change the font to
“symbol”, you will get the following symbols:
q w r u p a g l b n m W S D


to type “°”, go to the insert and symbol menu.
to superscript (x2) or subscript (x2), highlight the target, go to font and check the box