I am performing an experiment to find the piece of wire with the highest/ lowest conductivity, and the highest/ lowest resistance out of two samples. The two pieces of wire are Nickel Chrome and Constantin.

        

What We Did

Apparatus:         1 Power supply

                1 Voltmeter

                1 Ammeter

                6 Connector cables

                2 Crocodile clips

                1 meter long strip of wood with an attached 1 meter long wire of Nickel Chrome

                1 meter long strip of wood with an attached 1 meter long wire of Constantin

Measurements needed:        Amps

                        Volts

                        Centimetres

        Considering that in the ‘Length of Wire’ experiment, our strand of wire was 1 meter long and in 10cm segments, and there were 2 wire types, there was going to be a total of 20 measurements of Voltage, Amps and centimetres. In the thickness of the wire experiment, there were 2 wires, and 3 different thicknesses. Therefor there was a total of 6 measurements of Voltage and Amps, along with 6 equations to solve to find the resistance of each thickness. For the ‘Type of Wire’ experiment, we already had our measurements because we just had to use the same from the ‘Thickness of Wire’ experiment. So there were 6 measurements for this experiment aswell.

Plan of Investigation

        We first took the apparatus and assembled them in the way as shown (on next page). To get our results we had to first make sure that the two crocodile clips were holding the wire exactly 1 meter apart, and then took the readings from both the Voltmeter and the Ammeter. Next we changed the distance of the crocodile clips to 90cm and took the readings. Then 80cm, 70cm, 60cm and so on until we got to 10cm giving us 10 different results for the wire each time making sure that the distance between the clips was as accurate as possible. Once we had acquired all of our readings for one wire we progressed onto the next wire.

        We took 10m results for two wires and so moved onto the next experiment

        The next experiment we did was ‘Thickness of Wire’ experiment. This experiment will be done exactly the same as the previous, but we will be using 3 different thicknesses of each of the 2 wires. We will get one thickness of each wire, and attach our crocodile clips at each end of the wire making sure that they give the current the whole 1m of wire to run through.

        The last experiment we do not have to carry out because we have all of our results already from the previous test. All we have to do is make a table with headings of Wire Type, Wire Length, Wire Thickness, Voltage, Amps, and Resistance, fill it in, and then we have all of our results.

Fair Testing

        Usually when we are making sure a test is fair, we only change one thing.  In both tests however, we HAD to change two things. The type of the wire, and the length of the wire we had to change for the first test, and the type of wire and the thickness of the wire we had to change for the second. If we didn’t do this we wouldn’t have a test at all, never mind a fair one.

Results Tables on next page     

Obtaining Evidence

        

Safety

This experiment is not very dangerous however when working with electricity you need to keep safety first. Some of the main points are keeping the current low and safe as the wire WILL heat up as I found out. Handle equipment with dry hands, make sure circuit is totally connected before turning on the power otherwise touching a loose wire end may result in harm but should not if current is low enough.

Measuring

        We measured as carefully and accurately as possible to the naked eye using the apparatus of measurement we were given. However, we don’t know for sure that the apparatus we were given was as accurate as it needed to be. We measured over a suitable range of one meter, this gave us 10 results for each wire in the first experiment, and the more results you get the more accuracy you can get from your results. In the second experiment we only measure using three points per wire, and so we could have really done with a couple of more to make sure the further results followed suit.

Observations

We observed the readings on the voltmeter and ammeter as they changed however there wasn’t much of an increase in the ammeter at each stage of the experiment. We also observed a general increase in the voltage as the length of wire we use gets longer.

Analysing Evidence

Conclusion

Length

        I found out that as the length of the wire increases, so does the resistance against the current within the wire.

This is because when you make the wire longer, the current has further to travel thus increasing the resistance against the current. I can see this in my graph because the line is a mor or less straight one that passes through the point (0,0) on the graph

This means that the length of the wire is directly proportional to the resistance against the current within the wire. This means that when the length of the wire increases, the resistance against the current increases.

We can predict that this would be the same for both wires, and both thicknesses of the wirem hence we could make the statement that this pattern is the same for every wire in the world, with any length or any thickness. However to prove this fact we would have to test out more wires to get as many results as we can, and then make a more accurate statement

Width

 I found out that as the thickness of the wire increases, the resistance within the wire decreases. This is because the current has more space to move through when the wire is thicker. The electrons have more space to move from atom to atom instead of being compact into one thin wire where there isn’t as much space for electrons to move. Looking at my graph I can say that the relationship between the thickness of the wire, and the resistance against the current is not directly proportional. I can see this because on my graph the lines are not straight or reasonably straight, and they don’t pass through the point (0,0)

Type of Wire

        I found out that from the two types of wire we tested, Constantin gave out the least amount of resistance against the current. This means that Constantin is the better electrical conductor out of the two wires. The reason behind this is that Constantin lets electrons from within the current flow easier through itself than Nickel Chrome does. I drew a bar chart to show this data, and from the three thicknessess I used of each wire, Constantin gave out the least resistance against current for every thickness apart from the thickest we used, which was 0.90cm