Safety
- Handle the power supply carefully.
- I am going to only use a voltage of four volts so the wire will not burn
- Be careful when touching the wire, as it may be hot.
- Be careful when the wire is connected, as it will get hot.
- Be careful when cutting the wire.
- Make sure the mains to the power supply is switched off when removing the wire from the circuit to be measured.
Apparatus
Power Supply
two Multimeters
Wire
Meter Rule
Two Crocodile Clips
Connecting Wires
Preparation
Set up a circuit the same as this.
Cut wires to these specifications
10 cm x3
20 cm x3
30 cm x3
40 cm x3
50 cm x3
60 cm x3
Method
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Set up circuit as above
- Draw out a results table
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To improve the accuracy, I have decided to set up the circuit with the metre rule taped to the work surface. This will make it easier and more precise as I will not have to keep on holding the wire then putting the crocodile clips on. I have chosen to use a meter ruler because the lengths that I will be measuring are to big for a smaller ruler and the meter ruler can be accurate to +1mm. Make sure that the metre rule is actually one metre long and not one or two centimetres shorter.
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Use all the wires (18 in total)
- Record Results.
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To collect the data for my graph I have chosen to take a range 6 of lengths in which I have repeated 3 times each. I believe repeating the lengths 3 times and make an average for each length will give you reliable results
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Draw a graph of the average results
My Results
RESISTANCE = VOLTS/AMPS
My Graph
AnalysisIn my prediction, I stated that:If the length increases than the resistance will also increase in direct proportion to the length.
From my graph on the previous page, I can see that the resistance of the wire is directly proportional to the length of the wire. I know this because the linear Line of Best Fit if continued goes straight through the origin showing that if the length of the wire is increased then the resistance of the wire will also increase in proportion to each other. The line of best fit is a straight and it goes though (0,0) if there is no length, there is no resistance proving that the resistance of the wire is directly proportional to the length of the wire. This proves my prediction right.
The length of the wire affects the resistance of the wire because the number of atoms in the wire increases or decreases as the length of the wire increases or decreases in proportion.
The resistance of a wire depend on the amount of collisions the electrons have with the atoms. My graph proves that as the length of wire increases so does the resistance. This means in doubling the length of wire doubles the resistance and so on.
Evaluation
In the Analysis and the graph I have shown two main anomalous points, this means that there must have been a slight error in my experiment. As the wire, length is bigger at these points I found it harder to stretch the wire out and consequently, measure it accurately, an error also may have accrued due to any of these factors:
- Quality of that cut of wire
- Quality of voltmeter (as I didn’t get all the results in one day I may have had a different power supply’s therefore they wont all be at the same accuracy)
Although the graph is overall accurate and the results precise it is easy to see, the anomalous averages plotted because they do not all lie along the same best-fit line. The graph shows that my results are reliable as there are only two main anomalous points, (which are easily accounted for)
I think that my experiments went well. My results prove that my prediction was correct. All of the measurements that I took were very precise as I used multi-meters to measure both voltage and current this improves accuracy because it gives a LCD display of the readings to two decimal places. The pieces of wire I cut accuracy was increased as I had taped the rule to the worktop; I also had an adjudicator to check my measurements.
If I were to redo this experiment I would:
1. Use a more varied amount of lengths so I could emphasize the exactness of my prediction.
2. Use brand new batteries because they give DC (direct current) therefore giving a constant reading of the voltage.
If I did all these things my experiment would give excellent results therefore backing up again my prediction.