Noor Ahmed 10 C
Science
Mr. Hennard
5/10/11
Lab Write Up:
How the length of a wire affects its Resistance
Research Question:
How does the length of nichrome wire effect the over all resistance of a circuit?
Hypothesis:
This experiment will be discussing how the length of a piece of nichrome wire
affects the overall resistance of a circuit. The hypothesis for this experiment is this: as
the length of the nichrome wire shortens the amount of resistance will also decrease.
My reasoning for this hypothesis is that the amount of resistance in a wire increases
with a wire of longer length due to the fact that there becomes a larger distance for the
electrons to travel through, inevitably causing more collisions therefore slowing the
flow of electrons creating higher resistance.
Background information:
Dictionary definition of resistance: A measure of an object's reluctance to allow
charge to pass through it.
A piece of wire observably is created from and contains atoms. Upon closer
investigation, it is plain to see that the longer a piece of wire is the more atoms there
will be enclosed. When a circuit is connected to a battery source, which sends charge
through the path there is always the reluctance of the mediums sending charge
through it. The longer a wire attached to a circuit may be the higher the level of
resistance will be. The logic behind this is the fact that the electrons charging through
the wire will face more atom collisions in a longer wire, because there will be more
atoms to potentially bump into. In the same way a shorter piece of wire will carry a
fewer number of potential collisions because it is made up of fewer atoms.
Apparatus:
1.
2.
3.
4.
5.
6.
7.
8.
Voltmeter
Ammeter
105cm Nichrome wire
1 Meter Stick
2 5 cm. pieces of Scotch Tape
5 Leads
1 Battery Source
2 Crocodile Clips
Diagram:
Variables:
Type of
Variable
Variable
Independent Length of nichrome wire
Dependent
Control
Amount of resistance in
the circuit
1. The same Meter
stick
2. Type of wire
3. Thickness of the
wire
4. Leads/# of leads
5. Battery
6. Temperature of the
wire
7. Temperature of the
room
8. Crocodile clips/#
of crocodile clips
How the Variable is Manipulated, Measured or
Controlled
The nichrome wire will be cut to 105 centimeters,
and used for each trial and each measurement
throughout the entire experiment.
The change (or difference) in resistance is
essentially the base of what we are researching.
This will inevitably change as the length of the wire
gains/shrinks, in length.
1. In this experiment we will be using the same
meter stick just to make sure we do not
change anything unneeded.
2. The type of wire is imperative to maintain,
because the resistance of a wire changes
with its type. We also maintained this
because if there were any imperfections in
the wire it would affect all data and not just
one set.
3. The thickness of the wire will automatically
be the same with the type of wire. We are
not gathering any information about the
relation with wire thickness; if we changed
the thickness it would only obscure any data
we collect.
4. The number of leads we used was 5. We
used the same 5 reliable leads throughout
the experiment.
5. The battery should be the same every time
you take down information because the
amount of energy it is sending should be the
same, every time.
6. The temperature of the wire can change the
resistance so it is important that it remains
the same.
7. The conditions that you do you’re
experiment should always be the same since
slight changes can make a large difference.
8. We used the same 2 reliable crocodile clips.
Each of these variables is essentially being
controlled in order to have a proper a lab that we
can gain legitimate information from. No variable is
more important than another in insuring that we
have a fair test. It is imperative that one maintains
each of the variables in order to maximize the
validity of the data.
Fair Testing:
All of the control variables and use of apparatus allow us to maintain the
stability of the experiment to the greatest extent possible. This makes for a fair test
because you know that all of the data has been collected under the same terms. All of
the variables besides the independent and dependent need to remain the same because
if they are not then you have not conducted reliable information.
Method
This is where I will describe the steps needed in order to carry out this
experiment
1. Start out by collecting all of the listed apparatus needed to carry out the
experiment.
2. Draw a table resembling the one below (A as in amps, V as in Volts, and R as
in Resistance):
Wire Length
Trial 1
A
V
R
Trial 2
A
V
R
Trial 3
A
1 meter
75 cm.
50 cm.
25 cm.
10 cm.
3. Cut a 105-cm. piece of Nichrome wire and extend it across the meter stick.
Tape the ends the ends to the ends of the meter stick using one piece of the 5
cm. cut tape on each end.
V
R
4. Assemble the circuit as shown in the diagram, using the 5 leads, voltmeter,
ammeter, battery source, and nichrome wire strung meter stick.
5. Start completing your first trial for the first measurement by connecting the
extended leads to measure 1 meter of wire.
6. Turn the battery on to the lowest level.
7. Take down the information given for the amps and voltage.
8. Turn of the battery source and calculate the resistance for the first trial.
9. Turn the battery on again once having calculated the resistance and take down
the second trial of information for amps and voltage.
10. Repeat steps 8 and 9 for the third trial.
11. Once having completed the first interval of data move the leads (crocodile
clips) to fit the length of the next (75cm).
12. Repeat steps 5-9 to take down the data same as you did for the first interval.
13. Continue moving the leads every time you finish an interval of data, and
repeat steps 5-9 to take down the data.
14. Make sure you right down all of your results in the data table.
Data Collection:
Wire Length
1 meter
75 cm.
50 cm.
25 cm.
10 cm.
Trial 1
A
0.11
0.14
0.19
0.37
0.87
V
R
1.78
1.79
1.76
1.68
1.59
16.18
12.78
9.26
4.54
1.83
Trial 2
A
V
0.12
0.15
0.18
0.38
0.88
1.80
1.79
1.78
1.67
1.60
Data Analysis:
Resistance = Voltage/Amps (for every trial of ever value)
Data Presentation:
Attached
R
15
11.93
9.8
4.39
1.81
Trial 3
A
0.11
0.14
0.17
0.37
0.88
V
R
1.82
1.81
1.76
1.68
1.59
16.54
12.93
10.35
4.54
1.80
Conclusion:
The data present on the attached graph illustrates a reasonably reliable set of
data. Overall the line of best fit matches the data, laying against the line in a fairly
even manner. However there are two apparent odd bits of information. Trial two of
the first (1meter) test and trial three of the third (50 cm.) test seem to be the outliers of
the data. One could argue that these to point are relatively close to the lines, and that
could be so but in relation to the other trials of data they are out of the range, more
distant to the line and the other points. Overall however, the pattern of the data
matches hypothesis, being that as the wire shortens the resistance will also decrease. It
was interesting to see how large the difference was between 1 meter and 10 cm; the
slope of resistance was worthy of note because I initially thought perhaps it would
have been a smaller difference, between each interval. As a whole this has been a very
successful experiment that needs few implements to improve it for a second time.
Evaluation:
The experiment conducted consisted of positive and negatives that created the
final outcome. Inevitably small things didn’t go as planned, and there were things that
could have been improved, however I think on the whole the data was reliable. The
reason I feel this way is because although there we slight in accuracies the data in
general came out the way we wanted it to, and as a group we learned more about the
resistance in nichrome wire. I believe that all of the instruments we used to conduct
the experiment did their job properly and for this experiment that was sufficient.
Things that were subjectively off were the way that we did the trials and the
intervals that we tested. First off, every trial that we took we took by turning on and
off the battery and checking the reading another time. The reason this was a problem
was that it should have been the same every time, and ended up not working that way
and we took down varying results. We also planned on measuring 5 cm. instead of 10
cm. as our last value but the wire at that point was overheated and melted the tape
surrounding it so we decided on doing 10cm. instead. In the future it would probably
be best to tart with the smaller values and work our way up as opposed to the
opposite.
Improvements to the Method:
Weakness (Issue with method)
Collecting Larger Values First
Suggested Improvement to Method
If I was to go back and re-do the
experiment the first thing I would
improve would be to start with the lowest
value on the table. When doing the
experiment the first time, the nichrome
wire overheated at 5cm., began to steam
and melted the tape surrounding it.
Therefore we were not able to take down
3 trials of 5cm. and instead changed it to
10cm. In order to get the best results
going back I would probably start with
the lowest interval because it will not
have had the time to overheat and
Battery Level
inevitably burn when it comes time to
take down the data.
Perhaps a change that could improve the
experiment would be to change the level
at witch we tested our values. We kept
the battery on the lowest level and in the
future it might make an interesting
experiment to test how drastically the
change in charge can have an effect on
the resistance of the wire. It could
possibly make for a more accurate set of
data, due to the fact that you wouldn’t
just be turning the experiment on and off.