Resistance of a wire coursework Essay Example for Free

Resistance of a wire coursework Essay Then we measured the first measurement of resistance at 100a c, increasing the temperature too over 300a c. Taking s measurement at every 10a c. At one point in the investigation the heat started to melt the plastic coating around the wires, we quickly noticed this was a problem so we attached the wire to a clamp, this was to stop the bare wire touching the metal sand tray, as this would cause the resistance in the metal of the tray to be measured as well, this would cause the ammeter to short circuit. After collecting results, we plotted a scatter graph, drawing a line of best fit, we also indicated any anomalies. I took the photo myself Safety When doing our investigation we had to take into consideration the safety aspect, this is because we were using very high temperatures up to 300a c. We used safety goggles to protect our eyes from the heat, and in case of spitting from the water in the preliminary work, to the sand in the main experiment. We also kept or distance from the experiment to protect from heat and spitting just like the goggles. After we’d finished we left the equipment to cool before the technicians to clear away, with a safety sign. We also used heatproof mats so the worktop was protected, as well as this it protected glass or porcelain pieces of equipment from thermo-shock (high to low temperature, very quickly) http://www. amazing1. com/Graphics/oly-lsg-4-1. jpg Obtaining Evidence Before we began our real experiment we carried out preliminary work to find out what was the best was to test the resistance of a wire, or how we could. So we tried using temperature as something that would either increase of decrease the resistance. In our preliminary work we found that the resistance started to change when the temperature exceeded 90a c. However we found that this was a problem because we were using water to heat the coiled wire. Waters boiling point is 100a c so we had to discard the idea and change it. So we used a sand tray as sand has a much higher melting point then water. We also repeated many of the experiments as well as the preliminary work to find out whether or not this was just a case of human error, and that we didn’t need to change the experiment. Also in the temperature experiment we used Copper at first; we then used Nichrome as this has a much higher resistance so the results would not be as high. In my results we identified outliers, and also calculated a mean, or the average for all of the results for the change in length of wire/thickness. In the first experiments for length of wire we didn’t specify a length of time that we were going to measure resistance on the wire for, we just laid the wire on the other wire, however this would have heated the wire giving us less accurate results. I decided to change this by only touching the wire for 2 seconds at every 10cm, allowing enough time to obtain results, but not long enough for the wire to be heated. http://reprap. org/mediawiki/images/9/99/Blunt_step10. jpg Patterns In Results In our results there were many patterns shown, for example as the length of wire increased in the length/ width experiment so did the Resistance of the wire. As well as this as the temperature increased further and further, the resistance of the wire increased as well. These patterns both show that our predictions were correct. However in both of these experiments’ there were a few anomalies. For example lengths 130cm on 28 gauge wire, and 150cm on 36 gauge wire. In the temperature test, temp 140a c and 250a c were anomalies. Conclusion My results show that as the length and the thickness of the wire increased, so did the resistance, which supports what my prediction. This is shown because when the length of wire was 40cm long (28 gauge) the resistance average was 2. 9 ohms, at 100cm the resistance average was 5. 4 ohms and finally at 160cm the resistance average was 7. 9 ohms. This is then supported by the 36 gauge wire, at 40cm the resistance was 9. 2 ohms, at 100cm the resistance was 19. 2 ohms and at 160cm the resistance was 27. 7. This clearly shows that there is an increase in resistance when there is an increase in length. In the temperature experiment my results show that as the temperature increased so did the resistance of the wire, however there were a few anomalies in the experiment. At 100a c the resistance was 1. 5, as the temperature increased to 220a c the resistance was 3, however at 240a c the resistance was 2. 9, this shows an anomaly in the results. After the temperature increase again so did the resistance e.g. at 300a c the resistance was 3. 6 Overall I think that my conclusion supports what I wrote in my prediction. This is because I predicted that as the length/temperature was increased so would the resistance of the wire. My experiments were a success. However if I were to do this again I would repeat each of the experiments more times to eradicate any anomalies that may have occurred through the investigation. Evaluation I think that my investigation went well, this is because my results that I have gathered support what i wrote in my prediction. However they were a few problems in the experiment for example, when we increased the temperature one of the connecting wire began to melt, this was due to the wire been too close to the Bunsen’s flame. This made our experiment short circuit, meaning we had to start the investigation from scratch. Also in our length experiment the wire began to heat higher than we wanted because of the current in the circuit, this could have made our results less accurate. Although the wire may have heated more than we wanted I still believe that the results were very accurate, as we only had 4 outliers in all of our results. I think that the level of accuracy in my results is very high because we repeated each one of the experiments more than once. To increase the level of accuracy in the results I think that if I were to repeat the investigation I would repeat them more than just once; this allows you to eliminate any anomalies that occurred. There were a few anomalies in my experiment these were: 1. 130cm on 28 gauge wire 2. 150cm on 36 gauge wire 3. In the temperature test, temp 140a c and 250a c were anomalies I think the anomalies for the length experiment will have occurred because of human error e. g. not reading the results correctly, or touching the two wires together for too much time, this would cause the wire to heat up, causing a false reading of the resistance. In the temperature experiment, I think the anomalies may have also sprung from the connecting wire becoming too hot, meaning that the resistance would not have been the right reading. As well as this, if the connecting wires touched the side of the sand tray, this would cause the reading to be lower so this may have occurred at some point during the experiment. In the investigation we repeated some of the experiments more than once; this allowed me to make my results more reliable. Also it allowed us to eliminate anomalies. I think that I should have taken more results because I still have anomalies in my results. However I did check if my results were correct by repeating each of the experiments more than once. When I did repeat the experiments the results I got were identical apart from the anomalies which some of them did not occur more than once. This proves that by repeating them it reduced the number of mistakes made. I also think that the range of results I collected was sufficient to give me answers for my prediction and conclusion. If I had to use my results to as evidence to back up my conclusion then I would be very confident. This is because my evidence supported my prediction, and all of the evidence was clear and easy to show in many different ways, whether in a table, bar/line graph or in any other form of data representation. I believe that I could use my results as evidence because it clear, concise and is very easy to understand. Thing that I could do to improve my investigation would be to make sure that there was only one variable (one thing I was changing) and to ensure that all aspects of human error were eliminated before starting the experiments. One further experiment that I would do would be to use a wider range of material for the coil of wire to give me more evidence, such as how the material changes the resistance. 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