Physics Coursework - Factors that affect the resistance of brine-soaked paper

I will do six different experiments and each of these three times making a total of 18 experiments.

To find out the resistance I will take the reading of the current and the voltage each time and then divide the voltage by the current to get each resistance. I will then average the mean reading for each of the lengths.

Diagram:

RESULTS

For a graph of these results, please see the attached called Graph 1.

CONCLUSION

We can see from my results table that there is a clear positive correlation with the resistance and the length of brine-soaked paper. As the length increases, so does the resistance. From my graph, I can see that the positive correlation is quite strong, however I cannot tell whether the best fine line goes through the origin on my graph and therefore I cannot tell whether the correlation is directly proportional or not. It is also hard to plot where I think the best fit line should cross on the y-axis from this graph. To make the above notes clear in my graph and clearly explained, I shall do another set of experiments ranging from 1cm up to 4cm to add to my results table.

RESULTS 2

CONCLUSION 2

From these other sets of results I can now see that the same thing is happening again and now I will pull all the results together and put them into a results table then make a graph showing all the results on one graph and see whether the best fit line crosses  through the origin or not.

RESULTS all together:

The graph for all these results together is also attached, see Graph 2.

CONCLUSION RYDER

I can now tell from these results that I have done the experiments well as the averages are very near to the line of best fit and there are no odd results. I can see that the line of best fit does go through the origin. This is clear on both graphs 2 and 3 (see attached). There is a clear strong positive correlation from the results and we can see this on the graphs. If we look at graph 2 we can see that all our results were close together for each time we did the experiments. This is good as it gives us clear results and shows we did the experiments well. From graph 3 we can tell that the length and the resistance of brine-soaked paper are directly proportional.

My prediction was correct. As I increased the length of brine-soaked paper, the resistance did too. My prediction of the graph was also correct as we can see in both graphs 2 and 3.

EVALUATION

I think there were some weaknesses in our experiments. The bulldog clips were a little rusty and therefore this could have prevented all the current so affecting our results. The solution might well have evaporated during the nights and the warm whether making it slightly more concentrated. Using various different ammeters and voltmeters may have made a difference due to the sensitivity and use of them.

If I were to do this investigation again, I would overcome the above problems by using brand new bulldog clips and keeping using those ones all the time. I would keep the solution in a container that would keep it at a constant temperature. The circuit equipment, I would use new ones and keep them all through to know that they can not get damaged or be different.

We did not have any odd results. A few of them were spread apart slightly for example 3cm the highest and lowest had a difference of 0.72mA but the resistance worked them out to be more similar and the average was not strayed away from the line of best fit.

I am more certain that my conclusions are correct because we made sure that our experiments were fair each time and I looked and analysed my results and graphs before making my conclusions. Any experiment that I thought needed to be re-done or added. I did which makes me more certain that my conclusions are right.

To find out more about this investigation, I would do a lot more experiments using longer lengths too and I would do experiments for all the different factors I could have chosen for the concentration, width of paper and voltage.