Resistance of a Wire
...ngth of the wire, the resistance will double. This is because when the wire is half its length, there is half as much space for the electrons to move around freely. The same amount of current will go through the wire in double the amount of time, which means the resistance must be double. METHOD 1) Firstly assemble the apparatus needed: A power supply Connecting wires A rheostat An ammeter A voltmeter A 1000cm length of Nichrome 26 wire A meter rule Scissors 2) Set up the circuit as shown below. 3) Adjust the rheostat so the voltmeter reads 3.0v. This should be kept constant throughout the experiment. ANALYSIS I have drawn two graphs to show my results, one showing resistance plotted against width and the other showing resistance plotted against 1/width. The first graph shows that as the width is increased, the resistance is decreased. At first this decrease large but the curve becomes much flatter as it gets closer to zero ohms. The second graph shows that as the value for 1/width is increased, the resistance increases. It is a straight line that goes through the origin (0,0) which means that resistance is directly proportional to 1/width. This means that as 1/width is increased; the resistance increases by the same proportion. For my qualitative prediction I said that as the width of the graphite paper is reduced, the resistance increases. From the first graph, you can see that this is true. This proves that if the paper is less wide then there is less space for the electrons to move around freely so there is more resistance. In the graph, when the width was 2.0cm the resistance was 6250 and when the width was 1.0cm the resistance was 12500 . For my quantitative prediction I said that if I halve the width of the graphite paper, the resistance would double. This also proves to be true, for example when the width was 6cm the resistance was 1852 and when the width was 3cm the resistance was 4000 . It cannot be expected to be exactly double because there are many other factors that could slightly influence the results. This proves that if the paper is half as wide; there is half as much space for the electrons to move around freely so the resistance must be double. I did not obtain any anomalous results even though I did not average any of my results, as this would have made it much more difficult to see any anomalies. This meant that no repeats were necessary. I think that my results are certainly accurate enough to support a conclusion and I have included this in the analysis of the predictions. EVALUATION The experiment did work well and as I have already mentioned, I did not receive any anomalous results. All of the results were within reasonable experimental error of the line of best fit but the results were by no means perfect. During the experiment I noticed certain flaws in the method and if I were to repeat the experiment I would change some aspects of it. The main problem was in getting the correct width and length. Using scissors was simply not very accurate, if I could do it again I would use a shredding machine to cut the graphite paper accurately. I do not believe that the bulldog clips were very accurate because it was difficult to fix them at the correct length and angle. Another problem was that the resistance in the bulldog clips would have added to the overall resistance, making the resistance larger than it would have been. If I repeated the experiment I would have used partly transparent bulldog clips so I could see where I was attaching them and I would also measure the resistance of the bulldog clips before the experiment and minus it from the results. Repeating all of the widths again and producing an average of them would have made my results more accurate and instead of having 1cm s...