Although if the zero error is very small in proportion the result value then it is unnecessary to subtract it because it will make very little difference and may cause you to make errors in the calculation and so get fluctuating results. Safety: This is quite a safe experiment to undertake although you must always be careful when undergoing an experiment as careless mistakes can cause accidents and something dangerous you may not have foreseen could happen. There is an electrical current being used in this experiment although it is very small and cannot harm you.
Carbon is also being used in this experiment and according to its hazchem it can cause irritation of the respiratory tract if inhaled, mild irritation and redness on contact with skin and most seriously chronic exposure is known to cause disease and cancer of the lungs. This means you must be sensible when handling carbon and wash it of quickly is gets on your skin. What I will do to verify my Hypothesis: I am going to plot a graph of Length against resistance and Width against resistance. This what I expect them to look like: – Graph expected for Length against resistance: Graph expected for Width against resistance:
Graph of Resistance against reciprocal of Width: If the graphs I produce with my results look like this then I will have verified that length is proportional to resistance and width is inversely proportional to resistance. To prove that the width and resistance have a proportional relationship I have to draw a graph of width against the reciprocal of the resistance. This should then produce a straight line, which passes through zero proving proportionality. I will then look to see if one variable seems to have more effect on the resistance than the other and I think that length will have more effect.
If there are any strange looking results on my graph then I will repeat them and see of I can obtain a more consistent value and re-plot the corrected ones. I will then draw a line on the curve which seems most suitable for the results it will be either be a best fit straight line or a best fit curve. Conclusion: Length against resistance The graph I produced when investigating the effect of length on the resistance of a carbon track very nearly produced the shape I had expected, which was a straight line that passed through zero.
It seems to follow the shape I had expected exactly up to the carbon track length of 12cm where afterwards the readings are always slightly below what would have been expected. This may be down the inconsistency of the carbon track, which may have had thicker carbon in the track over 12cm, and the resistance would be slightly lower than the rest of the readings because of this. Although when a best-fit line was drawn onto the graph that dissected all of the readings in half it did produce a straight line but this did not quite pass through zero but as shown on the graph it came very close.
This means that my hypothesis was approximately true and the small error can be explained by the degree of experimental error in this experiment, which I will look into in the evaluation. The shape of the graph suggests to me that length and resistance have a proportional relationship and this means that my idea was also correct. I know that they are proportional because the graph shows a straight line that approximately passes through zero, which indicates proportionality. If two variables are proportional it means that the ratio between them always remains the same.
Eg. 1 : 3 or 3 : 9 or 10 : 30. The shape of the graph also tells me that resistance of the carbon track increases as the length increases, I know this because the line is sloping upwards. Conclusion: Width against Resistance The width against resistance graph I produced was only roughly the shape I had expected as there were a few anomalous readings, which threw of the general pattern slightly. Although when I plotted best-fit line it made the pattern much clearer and it was almost exactly how I expected it to be.