Resistance Of A Wire

Evaluation

Evaluation Experiment one: This experiment was quite accurate, as when it is compared to the manufactures line which is on the same graph, we can see that this line is at most only 0.4? different form the manufactures line. This is a percentage difference of approximately 8%, using the formula: Difference ? original X 100 This shows that the results were good, as 8% is a very small margin of error. The error bars on the graph show that the most inaccurate result was the 60cm result. This could be down to an error in the measurement of the wire or a temperature rise. The two results for 100cm are exactly the same, and it is near to the manufacture's line, so this is the most accurate point.

The other three readings have almost the same inaccuracy, an average of 10%, which again, is fairly accurate. The inaccuracy could have been because of the wire coming from a different manufacturer to the predicted results, as there is some discrepancy between the amount of copper and nickel in different brand's wire. The ammeters and voltmeters could have been damaged and reading falsely on both the meters used.

Measuring the lengths of the wire is also a inaccuracy as the rulers used are not exact, and it is difficult to get an accurate reading of length by eye, as the wire might not be completely straight, it may be of different thicknesses throughout the length. These would have contributed as well to the error. These results would be difficult to improve on as they are reasonably accurate, and there were no anomalous results. But if I were to do this experiment again, I would use newer, more accurate ammeters and voltmeters, a more accurate method of measurement, and take a much wider range of readings, and more readings so that a more accurate average can be taken.

I would also investigate other factors, such as temperature, voltage and current, and see how these effect the resistance. I would also do the experiments under different conditions such as temperature and pressure to see if it makes any difference to resistance. As these results had a range of only 5 readings, from 0-100cm, and were only repeated twice, and that the results are not 100%, accurate due to the errors discussed earlier, then I would say that these results are not strong enough to base a firm conclusion on because there are so many sources of error, which are explained earlier.

Experiment two - These results were not as accurate as experiment one. I had predicted that the resistance should halve as area doubles, which it does, however not to the predicted curve. When the resistance is 24ohms, the % inaccuracy is 6%, and when the resistance is 6 ohms, the inaccuracy is 8%. These inaccuracies are fairly large. The error bars, however, are too small to be drawn accurately on the graph. They are at most