Calcium carbonate and hydrochloric acid Essay
Calcium carbonate and hydrochloric acid
Accuracy & Methods of Improvement Although it was generally an accurate and fair experiment there were bound to be some inaccuracies and errors. One that was difficult to completely stamp out was where the crocodile clip was placed. For example, at a length of 90cm if the end of the clip was fixed exactly on the 90cm mark, the actual length that current was flowing through may be 90. 3cm since the clip head is 3mm wide. This is why we measured the wire to two significant figures, so it rules out any inaccuracy that could be caused by the thickness of the crocodile clip.
To improve this inaccuracy we could use an item which connects the circuit to the wire with just a pinpoint. A way of tackling this problem is by having something in between the crocodile clip and wire such as a coin. The crocodile clip would in this case, be attached to a coin and the edge of the coin can be held down on the various points on the wire. This means the connection is much thinner and it enhances overall accuracy. This would then improve the precision of the measurements, as that point would be connected exactly on the correct length.
Another inaccuracy that could have affected the results is also linked with the length of the wire but not how well we measured it. When the wire was attached to the metre stick, some minor coils may have remained so when the lengths were taken the actual length would be different, since the wire would not be totally flattened out. Although this error would affect all the results so there would be no discrepancy between any readings because of this, it would still affect the overall results obtained and could pose a slightly incorrect trend when plotted on the graph.
There is one major way to reduce inconsistencies with any experiment. This is to repeat the experiment more times, as this is a process which increases the chance of obtaining enhanced accuracy with the results. By having more readings trends can be noticed more easily and even minor anomalies can be identified, and consequently stamped out. It then improves all round accuracy, as the average is more precise, since it takes into account all the readings that are taken. This provides an accurate and more reliable final calculation, which is the resistance in this investigation. Extending the Experiment
Although we have identified the inaccuracies with this experiment, there are ways we can extend this particular experiment, which will still be investigating the effect of different lengths of wire on its resistance. One way we could do this is to repeat the experiment but with a longer piece of wire. So the lengths of wire could be taken every 10cm, starting from a length of 200cm. This would show whether the trend between length and resistance is still true when the overall length of wire is longer. This experiment would have 20 readings if the lengths were taken every 10cm.
Similar to the original experiment, a clear trend could then be obtained from these results. Another experiment we could carry out is to again repeat the original experiment, but using a wire of another material, such as a copper wire. This would be to show whether the trend obtained using the constantan wire, is true for other metals as well. By doing this experiment we can see how resistance changes with length, according to the material. So even if resistance increases with length for both wires, we can see how much the resistance changes from one reading to the next reading from each set of results.
For example, the second wire may also follow the same trend, but the average difference between the resistance at each reading may only be 0. 1, whereas the resistance with constantan changed much more significantly. This would ultimately show how the resistance/cm of wire is different for the various materials investigated. Another Similar Experiment As well as improving and extending this experiment we could carry out other experiments to determine which other factors affect the resistance of a wire such as the material.
One such experiment could be to investigate how temperature affects resistance. Since the effect of temperature is investigated all the other variables would be controlled. Many things have to be decided so that the practical remains a fair test, such as a suitable material and length for the wire and a value for the current, e. g. 0. 20A. These would all remain constant throughout the experiment while the temperature varies. In this investigation the chosen length of wire would be used to carry out the experiment but at different temperatures.
For example, if the chosen temperatures are taken at every 5 degrees Celsius from 20 up to 65, a water bath will be required. The water bath would first be set to 20 Celsius and the wire will be placed in that. After controlling the necessary variables the reading for the potential difference should be taken. The water bath will then be heated to 25 Celsius and the procedure will be repeated. This process would be repeated at the various temperatures, and then the experiment would be carried out a second time for enhanced accuracy.
Finally the resistance can be calculated from the average of the voltage readings. I predict that as temperature rises so will the resistance. This is partly explained by the kinetic and particle theory, because when temperature rises there is more kinetic energy in the atoms of the wire so they vibrate more frequently, increasing the number of collisions with the flowing electrons. Hence resistance increases. This experiment is a way of showing and conforming this theory. The next page shows a typical format for the results table of this experiment:
Temp. (Degrees Celsius) Current (A) Potential Difference 1 (V) Potential Difference 2 (V) Average of PD (V) Resistance () 20 I expect that the graph obtained from this experiment would not be a straight line, but a curve whose steepness increases as the temperature increases. This is because when the temperature is increased the atoms of the wire vibrate with greater frequency, to increase the resistance.
However, although the temperature is increased evenly, the frequency with which the atoms in the wire vibrate rises sharply but not proportionally. This is why the graph would be a curve and not a linear graph. Graph obtained & Anomalies By looking at the distribution of points around the line of best fit, I can see that our results had no major anomaly as all the points are fairly close to the line. However, the resistance values I obtained with the length of wire at 75cm and 80cm, were two points that are slightly distant from the, compared to the other readings.
This was probably merely a random error as there is no specific reason for the calculations at those particular lengths to be slightly inaccurate. Other than that there were no anomalous results since all the points on the graph are more or less situated near the line of best fit. Based on the theory, I predicted that the line on my graph would go through the origin. However, it does not intercept the origin, which means that there has been a minor systematic error somewhere during the experiment. A likely error could be linked with the connections of the wire to the circuit.
Since the crocodile clips are not very precise and the connection to the wire is therefore loose, there may have been air in between the connections which would have increased the overall resistance, because the reading would have included the resistance of the clips. Since this inaccuracy would have affected the entire set of results, this may have pushed my entire graph up so that it doesn’t go through the origin. One way of resolving this problem is to solder the clip onto the wire, to prevent air between the connections.
Another method id by using something with a smaller surface are so the point in contact with the wire is more exact. This would improve accuracy and not let other minor factors affect the resistance measured. Overall, by looking at the way I carried out the experiment and the results I obtained, I think the investigation was successful and displays a true pattern of how the length of a wire affects its resistance. However, as I have identified, there are many other ways that I could have carried out in order to improve the reliability and obtain more accurate results.
University/College: University of Arkansas System
Type of paper: Thesis/Dissertation Chapter
Date: 12 October 2017
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