The circuit should be set up as in the circuit diagram below. It is important that the ammeter is set up in series.
To ensure that the investigation is carried out in a fair way and that the results will be accurate and reliable, a number of points must be considered.
The only variable in the test will be the length of the wire. The wire must be pulled tight against the ruler to ensure the length is accurately measured. The same circuit must be used throughout the experiment, as a different circuit may be more effective than the other (eg. Series and Parallel). The same wires should be used; both the Constantan wire and the wire used to connect the components together, as different wires may have different amounts of resistance. The Ammeter should also be used, so that any resistance affects all the results. The power supply should be set up at 1V before the tests begin, and then left, so as the current being provided, is always the same. All equipment and conditions should remain the same. The experiment will be repeated 3 times and an average taken to make sure that the results are reliable.
I predict that the longer the piece of wire, the greater the resistance will be. This would be due to the freely moving electrons being resisted by the atoms in the wire. In a longer piece of wire, there would be more atoms for the electrons to be resisted by and so the resistance would be greater.
The relationship between the wire length and the resistance should be directly proportional and follow a trend or ratio. This is because in a wire that is twice the length of another wire, you would expect double the amount of atoms causing the resistance. For example, in a 40cm wire, the electrons would have to travel double the distance than if travelling through a 20cm wire. This would mean double the amount of atoms that the electrons would collide with and therefore the resistance would double.
Here are our preliminary results:
The table below shows the actual results.
Here is a line graph to show our results.
The results from the graph give a clear indication of how the length of the wire alters the amount of current flowing. There is clearly a reasonably strong negative correlation, which proves that when the length of the wire increases, the current that flows in the circuit decreases. The results that I have obtained from this experiment have supported my prediction, that “the longer the piece of wire, the greater the resistance will be” and my theory for this has been explained in my prediction. So the results have shown that my prediction was true.
The line of best fit shows that the results generally followed the expected pattern, which was that the wire length and the resistance should be directly proportional and follow a trend. The points are fairly close to the line, which shows how they were fairly proportional. Some, however, are slightly further away from this line, which would suggest that they are less proportional.
As mentioned, we used the same equipment to conduct the experiment. Our wire was, in places a bit worn and crinkled, which could have added to the resistance, meaning that the current would have had a harder job to get from one end to the other. Our power supply was set to 1V, and was unadjustable, which meant that the current was unadjustable, so we just had to trust that this was going to stay the same.
We had no anomalous results, however there were some unexpected results that we did get, the first two particularly. These were accurate results, however they did not fit on the line of best fit, and therefore do not follow the expected pattern exactly.
This experiment was a success, and proved that the longer the piece of wire, the greater the resistance will be.
I could use a similar circuit to find the amount of resistance that each length of wire had on a circuit, or find out how the thickness of constantan wire will alter the amount of current that flows through the circuit. To find the amount of resistance that each length of wire had, I would need to use a voltmeter, and then to find out how the thickness affects the amount of current, I would need different thicknesses of the wire.
Chris Foulkes 10 Otter Page of
