Safety: I feel that to make the experiment a safe one I will keep the crocodile clips upright so that they don’t touch anything else and short circuit. Also I will only turn the circuit on when taking readings so that people don’t play and get electric shocks and so it doesn’t overheat.
Reliability: To make it reliable I will take each reading of the same length three times but try different positions, if the readings are very different I have done it wrong, if they are different by a decimal point then I can say they are reliable but not always correct.
Accuracy: I can make it accurate by measuring the length of the wire to the nearest millimeter. I can also use digital meters so that I have the closest measurement I can get. I could also use a stopwatch so that I could take the readings after the same amount of time.
Processing Results: In the preliminary experiment I had three different wires with three different types of thickness. I had three tables to go with the wires and I had to calculate the average resistance of the three wires. To do this I used the mean by adding the results of one of the wires (which I did three times, but in different positions) and divided by three. This gave me an average for each wire and I intend to do this with the different lengths of this experiment.
Conclusion: The resistance increased with length just as I predicted in my prediction. This is because the further the length of the wire then the further the electrons have to jump. For example, if the length was of the wire was 30.0cm (to the nearest millimeter) and the resistance is 6.2Ω, then the resistance of the wire will have increased if the wire was at 120.0cm, which has a resistance of 13.2Ω, which clearly shows what I said was true.
If you look at the graph then you can see I have strong positive correlation except for the first four averages I have collected. I have come to the conclusion that this can be the result of three things.
- The voltmeter, which we had, was broken and it finally packed in around the 50.0 – 60.0cm mark.
- We didn’t measure as close to the nearest millimeter as we had hoped and
- The temperature of the wire had increased and therefore affected the resistance of the wire.
In the prediction I predicted that the resistance of the wire would rise with the length which it did. I was able to predict this with the help of the preliminary experiment, investigating the resistance of the wires made from different metals, because in it we used the same length of wire for the whole experiment (60.0cm). From this I had a 50/50 chance of getting it right and with a bit of logic and this diagram,
I was got it right.
The diagram helped because it shows the movement of the electrons. The electrons are negative and they move from right to left. This is because the two negatives repel each other and the electrons are pushed to the positive side by the repelling force. As they reach the positive side they are pushed round and round. Also, as we carried on with the experiment the wire heated and the electrons started to move faster. As they move faster it gets harder for them to jump and land which also affects the resistance.
If you look at the graph there is two lines on it (a pencil line and a red ink line) these represent the two different results. The red ink line is the results from ‘physics by experiment’ which is what the graph is supposed to look like. The pencil line is my results that I collected. Just from looking at the graph I can tell that my results were reliable, because they go basically side by side, but not accurate, because they do not go directly on top of each other. This can be the result of two things,
- The wire was at a different temperature to the one in ‘physics by experiment’ and
- My measurements weren’t as accurate as the ones in the book.
Evaluation: If you look at the graph that I have drawn you can see that the first four results are anomalous and are away from the other marks. This is because we had a broken voltmeter, which we had to change when we got to about 50.0 or 60.0cm. After we changed the voltmeter our results seemed to go on course and be just of the mark with the ‘physics by experiment’ results.
I feel that my results were very reliable but not very accurate. The first four set of averages I had were basically the same and varied from a couple of decimal points which are reliable but not accurate. The results of the rest of the points were more accurate just not as accurate as they could be, if you look at the graph (the red ink line), but I think they were very reliable. The most they varied from was on the last reading which was one whole Ω from 13.8Ω to 14.8Ω.
I feel the conclusion I came to was the best I, personally, could have come to. I also feel that I could have had a better and more accurate conclusion if I had extended my experiment into lengths of over two meters and up. To make it even more accurate I could have tried using different metals and different types of thickness for example, using constanton with SWG (Standard Wire Gage) 24, 28 or even 36 to get a wider range of results. After doing that I could have declared that,
“Resistance rises with length”.
I could say that now but I don’t know that if I get to a certain length it might stop rising and just stay the same from there onwards.