The Apparatus I will use are
- Wires
- Crocodile Clips
- Nichrome wire (max length of 100cm (1m))
- Voltmeter
- Ammeter
- Variable resistor
- Cell (battery)
- Ruler
- Wire Cutters
The circuit will be set up like this:
These are the results from using a computer simulated program. Unfortunately the current varied on this program. This is where these results will differ from mine as our currents will all ways be the same. From these results I am see that by choosing an interval size of 10cm is good, as there is a good difference between results, and there will not be many points that need to be plotted on a graph.
Step by step Instructions
- Set circuit up (pictured above)
- Use 100cm (1m) Nichrome wire of 0.26mm width
- Record readings on ammeter and voltmeter and work out resistance using formula.
R = V/I.
- Repeat steps one and two with 90, 80, 70, 60, 50, 40, 30, 20 and 10cm of Nichrome wire.
- Redo the whole experiment to get secondary answers.
- Change the width of the Nichrome wire 0.32mm wire and follow the same instructions.
Prediction:
I will predict what happens for each variable in a paragraph each, and then try and link the two together so form a final prediction of what I think will happen when changing length and width of the wirer.
Length:
I predict the longer the wirer the higher the resistance will be. This is because the wire is built up of atoms; within those atoms at the centre in the nucleus are protons (p+) as well as neutrons. As electrons (e-) pass the atoms they are attracted to the protons (p+). (As shown by magnets opposites attract so e- is attracted to p+) Most of the protons and electrons do not join as the charge pulling the electrons round the circuit is stronger. Even though some of the p+ and e- do not join there is enough attraction there to slow the e- down. This means that it takes more time for the charge of e- to get round the circuit.
Current= charge/time
Width:
I predict the thicker the wirer the less resistance there will be. The e- (electrons) will still be attracted to the p+ so this will still cause the current to slow down. But there is a larger area in which e- can pass. This means more e- can pass a certain area during a period of time, meaning the charge takes less time to get round the circuit. This should mean that the Nichrome wire is thicker than the other wire in the circuit, the current should be increased (only if though)
There are two factors which will affect both kinds of wire these are
Heat will not affect this experiment as I am using variable resistors to make sure that the current stays the same. This means they will not be a higher current so there will not be temperature increases.
As electrons are negative (-) and protons are positive (+) I think that some of them will join together. Some of the e- ions will join the p+ ions. This will make the charge decrease, as less e- will be getting back to the cell (battery)
So as the lengths decrease so does the resistance. The resistance should be proportional to the length. The wider the wire the less resistance, this means if there is a length of 100cm and a thick and thin wire the resistance of the thinner wire will be greater.
In thin wire the electrons do not have much space to move around the Metal atoms.
In thick wire electrons have a lot of space to move around the Atoms.
Measurements:
I have used a computer program to simulate the experiment. I will try different intervals in which my wire will be cut. I want an interval which gives good variation, while also not having too many results that it will take a lot of time to produce a hand written graph.
From these results I have decided that 10cm intervals give the best intervals to the amount of results collected. The only problem with using the simulator is that the current varies; this means heat plays a factor in the resistance, and the calculations to work out the answers are harder.
These are the results from my Experiment.
Analysis:
From the graphs I have produced I can see that the results have a very good positive correlation. With both graphs there are no completely irrational points marked. From the two individual graphs there prove my first prediction correct “I predict the longer the wirer the higher the resistance will be”. This is justified by the graph, because as the lengths get longer, the graph climbs. Showing that the longer the Wire the higher the mark, meaning the higher the resistance.
My second prediction “I predict the thicker the wire the less resistance there will be”. The results prove this correct. To help show this I plotted both results on the same grid. This showed how the resistance of one wire was much higher than another. The Higher resistance came from the results of the thinner wire. Meaning the thicker wire had less resistance on the flowing electrons. The table above also shows how the resistance altered between the two thicknesses.
The thickness of the wire can be seen as directly proportional:
Thicker: 20=k 5 20 5 = 4 K= 4 4x5= 20
Thinner: 20= K 1.25 20 1.25 = 16 K= 16 16x1.25= 20
Evaluation:
I think the experiment that me and my partner did was very successful. At the start of the investigation me and my partner realised the variables which were about to change. We decided on changing two variables. By changing two meant that a lot of changes could occur and the whole experiment could get complicated. By setting up a specific plan with details on how to do the experiments it allowed us to be organised and run the experiments so the results were not compromised. The accuracy of our experiment was shown by our results, when we repeated them afterwards they gave the exact same results. That shows how our measuring was very accurate. When choosing variables I was going to change, I realised that the current running though the circuit was likely to change, either because the battery (cell) was running out, or that we used a different battery (cell) as we didn’t complete all the testing in one day. By the current charging meant that it affected the heat of the wirer. By the temperature of the wirer changing meant that the flow of electrons flowing though it would be affected. The only way in which my partner and I could keep the same current round the circuit was to use variable resistors. This meant by using an Ammeter and a Variable resistor, we could choose a current in which we wanted, and then maintain it though out.
As we were attaching the Nichrome wire with crocodile clips we had to make sure that the distance between the ends of the clips was always the distance we wanted. Each time we measured a length we had to add 1cm to it. By doing this meant that 0.5cm each side could be used to secure the Nichrome wire to the crocodile clips, without having an inaccurate length.
To make sure the accuracy of our results were as best as possible we recorded all the results to two decimal places. This helped make clear differences between the gaps in the results, as at some points the voltage decreased by 0.06 Volts. Without going to 2d.p would have meant that this difference would not have been noticed.
To make sure that the results were reliable we ran did the experiment twice. This meant that if there was a massage difference in results then we could find the average and use that to plot a graph. As it turned out our results were exactly the same. This meant that time wasn’t needed working out the average.
To help show the difference in resistance between the two thicknesses of wirer I plotted the results on the same graph. This allows the interpreter to see the extent of the difference.
I do not think there could have been any improvements in the way we ran the experiment, as our results are accurate, and show good correlation. I think we could improve the lengths and widths of the wirer. By having longer and thicker/thinner wire would mean that the results would be extended. If we investigated 4 different widths, and lengths up to 200cms in gaps of 10cms, and then also change the current, it would give us sufficient results to be able to form a formula which would be able to incorporate different lengths/widths/current of Nichrome wirer, and give what the resistance of it would be, without having to do an experiment.
By doing this investigation has helped me understand how electrons flow in circuits, and understand how the number of metal atoms within a wirer also affects the flow of charge around a circuit. This investigation is about physics, but has helped me understand chemistry better, as I understand how the atom is built, and how its protons affect the electrons.