Prediction:
I predict that lengthening the wire will increase the resistance in proportion to the length. I
think this because the longer the wire the more ions inside it and so the more likely the electrons are going to collide with the ions. So if the length is doubled the resistance should also double. This is because if the length is doubled the number of ions inside the wire will also double resulting in twice the number of collisions slowing the electrons down and increasing the resistance. When turning on the voltage to a circuit the electrons lose energy as they pass though the wire because they collide with the atoms, slowing them so then causing more resistance. So the longer the wire the greater the resistance.
Metals conduct electricity because the atoms in them do not hold on to their electrons very well, and so creating free electrons, carrying a negative charge to jump along the line of atoms in a wire. Resistance is caused when these electrons flowing towards the positive have to jump atoms. So if we double the length of a wire, the number of atoms in the wire should double, so the number of jumps double, so twice the amount of energy is required: There are twice as many jumps if the wire is twice as long.
This is a graph of my predicted results it shows that the length is proportional to the resistance.
Results:
Graph on separate sheet
The graph is a straight line through the origin, which means the resistance is directly proportional to the length. This means that if the length is 40cm, and resistance is 2. Then if length is doubled to 80cm, resistance also doubles to 4. My results are not perfect but show this quite accurately.
This is because of the scientific idea, stated in the planning that if you double length, you double the number of ions in it, so doubling the number of electron jumps, which causes resistance.
The results support my predictions well, the results turned out the way I had expected, they match the predicted line well. I had predicted a straight line through the origin.
As you can see each wire is made up from rows of ions keeping its structure and its ability to be electrical. Once passing a current though it the electrons pass though causing an electrical current. The electrons have to pass though the ions, which can cause resistance. The longer the wire is the more ions there is to pass though so slowing down the electrons down as they collide with each other and the ions.
Conclusion/ Analysis:
From the graph on the previous page I can see that the resistance of the wire is proportional to the length of the wire. I know this because the Line of Best Fit is a straight line showing that if the length of the wire is increased then the resistance of the wire will also increase.
This experiment was quite accurate. There were no anomalous results on the graph but there was a most inaccurate result at 40cm. 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, which shows the longer the wire the higher the accuracy.
I did the test 3 times each to improve accuracy but the inaccuracy in some results could have been because of the wire being to long and it is difficult to get an accurate reading of length by eye. maybe the wire might have 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. I would use a digital voltmeter instead of an analogue meter. I would do this because a digital voltmeter is a lot more accurate than an analogue because if the needle in the analogue voltmeter is bent then the readings given off will be false whereas a digital voltmeter does not rely on a needle or any other manual movements. The wire might not be completely straight, it may be of different thickness throughout the length. These would have contributed as well to an 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.
