I predict that in the experiments, the wire with a larger diameter will allow the electricity to flow easier, and therefore let a greater current to pass through at each voltage. This is because of the increased amount of energy that can flow through the wire at any one time, as more electrons are free to move.
I think that there will be a relationship that we can find between the current in different wires or the current and the voltage in the same wire, such as when the voltage doubles, the current doubles; or when the diameter doubles, the current doubles. However, I am not sure what the relationship will be, although I believe there will be one.
To ensure a good, detailed investigation, we should use at least three or four different diameters of wire, repeating each at least twice.
Specialised safety equipment will not be needed, but as always, we should be careful with mains electricity. We should also beware of the fact that bare wires will be used in the experiment, and they will heat up during the experimentation, due to resistance in the wires, and this could easily burn us or even start a fire if we are careless.
I think that the equipment we have selected will allow us to complete the experiment safely and successfully. The different diameters of wire will mean that in each case, a different amount of electrons will be able to flow through the wire, as shown below.
The reason the electricity can flow through the wire, is because of the free electrons that are lost when the metal atoms in the wire bond with each other, forming ions, cations (positive ions) to be specific. Copper has one electron on its outer shell, so it can lose this and form a sea of delocalised electrons, which can conduct electricity. They do this by flowing through the wire, towards the positive terminal of the power pack, because the electrons are negatively charged.
Observations
When we did the experiment, we used the equipment mentioned in the Apparatus, and successfully obtained the following results:
Wire Diameter: 20s.w.g.
1.42mm ; 1.41mm ; 1.41mm ; Average : 1.413mm
Wire Diameter: 24s.w.g.
1.05mm ; 1.05mm ; 1.06mm ; Average : 1.053mm
Wire Diameter: 32s.w.g.
0.25mm ; 0.255mm ; 0.25mm ; Average : 0.252mm
Wire Diameter: 36s.w.g.
0.185mm ; 0.185mm ; 0.185mm ; Average : 0.185mm
Wire Diameter: 38s.w.g.
0.145mm ; 0.15mm ; 0.15mm ; Average: 0.148mm
Analysis
Looking at these results, we can see that the thinner wire allow smaller currents. We an also see that the current increases as the voltage increases.
If we examine the graph (below), we can see there is an obvious relationship between P.D. and the current. As the P.D. increases, the current increases. We can also see that the current is smaller in the thinner wires, such as the 38s.w.g.. This is because of the restricted flow of electricity, due to the lower number of free electrons in the wire.
Comparing this to the original prediction, we can see that they match up fairly well, as I said, "the wire with a larger diameter will allow the electricity to flow easier, and therefore let a larger current flow with each voltage." Looking at the results tables and the graph, we can see that this is fully supported.
Looking at the results we can see that there may be a relationship between the current in a wire at a voltage and the current in the same wire at a different voltage. For example, at 1.0V, the current in the 24s.w.g. wire is 0.98A, and at 2.0V, it is 1.96A, which is about double the current at 1.0V. Therefore the relationship between the current and the voltage in the same wire is, as the voltage is doubled, the current is approximately doubled as well.
As I explained in the Planning section, the amount of current that can pass through the wire depends upon the number of delocalised electrons, which In turn is determined by the number of copper atoms, or the width of the wire. This is demonstrated below:
This flow of electrons is due to the copper atoms losing the electron on their outer shell, as it is in an arrangement that allows fairly easy loss of one electron. This arrangement is because of copper's proton number, 27, so the electron configuration is 2,8,15,1. There is only one electron in the outer shell.
Evaluation
I think the procedure was fairly good and accurate, but could have been improved. The results we achieved were also fairly good as we did not find any anomalies.
Most of the points on the graph were either perfectly on top of the lines of best fit or very close to them. The only inaccuracies were at the smaller currents, such as with the 36s.w.g. and the 38s.w.g. wires.
As I mentioned, the procedure was good, although it could have been improved by repeating the measurements, in order to get more accurate results. We could have used different, more accurate meters as well, or if we had used a more efficient set of equipment, with less resistance.
I find that the evidence is reliable enough, and since there are no anomalous results, we can assume a firm conclusion can be made.
As additional evidence is concerned, we could have repeated all the results with a different set of equipment, including different wires and power pack. In order to extend the experiment, we could try one wire, but with different length, and find out if that affects the current when we change the P.D., for example, we could try the 32s.w.g. wire at 10 cm, 20 cm, 30 cm, 40 cm, and 50 cm.
In order to improve the original experiment, we could have made sure that there was always a good connection between the wire and the crocodile clips, by using crocodile clips with a stronger spring, or sellotaping the parts together, or both. Another improvement would be allowing more time for the experiment, so that we could have repeated all of the measurements again, and taken our time more.
