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ANALYSING From this experiment I have found out that there are different factors that affect the resistance of a wire. The factors that I have investigated are the length and thickness of a wire. In the experiment, as the wire got shorter, the resistance decreased, and if the wire were increased then the resistance would increase too. If the thickness of a wire were to be changed then the thicker the wire, the less resistance and the thinner the wire the more resistance it will have. I have also found out that the resistance is calculated by dividing the voltage by the current.
This calculation was used in my experiment and showed that the resistance is roughly constant. If some odd results were obtained, it was because at a low voltage the power packs are inaccurate and at a high current, we might gain a heating effect. Ohm’s law can be proved by the graph due to the fact that the graph has a straight line; therefore it has a constant gradient, meaning a constant resistance whatever current is passing through it, providing the temperature is constant. If the graph were a curved, then that would mean that the resistance was changing.
If that were the case the resistance could be found for any point by taking the pair of values (V, I) from the graph and sticking them in the formula R= V/I. (Information obtained from physics revision guide. ) That would be disobeying Ohm’s law. In my opinion, the resistance of the 32- copper wire seemed odd since the thinnest wire is supposed to have the highest resistance. However a good conductor, which is what copper is, will allow current to flow through it easily. Therefore that’s why the ammeter reading for the copper wire, which measures the current, was very high, compared to the reading of the other types of wire.
A nichrome wire would have more resistance than a copper wire of the same size, because less current flows through it, making it not such a good conductor. We can also conclude that the thickest wire, type 26, had the highest resistance because less current could flow through it. EVALUATING: This investigation was conducted following the method above. By following those steps, I managed to obtain more than enough readings to plot a graph with and I managed to obtain accurate results, until the wire reached 30cm (TABLE 1). However my previous readings were fairly accurate, which were more enough for me to plot a graph with.
I had seven readings when only 6 are needed to plot a graph. The results of the first experiment my group conducted, (TABLE 2) were much more accurate than the second one (TABLE 1). The resistance was very constant, however we did not complete the experiment. We planned to carry it on the next lesson, but it would not have been a fair test because we used a different power pack and the voltage was not the same. We found out that we were getting odd results to our previous ones; therefore we had to start the whole thing again.
We made sure we finished that experiment and even had time to conduct another: an investigation to find out whether the thickness of a wire would affect the resistance. Since I only had to investigate five different wires, obtaining five results, this investigation was easier to conduct because there were fewer to do and I knew exactly what I was doing. It took me less time to set up the circuit and it was definitely a fair test. However when it came to the 32-copper wire the resistance was very high. I expected it to be high because it was one of the thinnest wires, however not that high.
I suspect I either recorded the wrong reading or because at low voltage the power pack was inaccurate and at high current there was a heating effect. However, as I mentioned in the analysing section, there was a simpler explanation. From previous work, I remembered copper is a very good conductor, therefore the high current reading. In future if I conduct another similar experiment to this one there are some improvements that could be made: I could compare my results with other people to see if they got the same or near enough results.
That way I would know whether I was on the right tracks. If I am stuck on connecting the circuit, I could draw a diagram first and follow that. I should finish every experiment the same day; so that I get more accurate results and can compare the results to the results of another experiment, on the same subject and would not have waste time having to start the same experiment again. I could have done some further research and find out what and if there are any other factors that affect the resistance of a wire and then I could have conducted an experiment.