Measurements
I will need to measure quite a few things during this experiment. Length of the wires id one thing I will need to measure, and I will use a meter ruler for this purpose. Voltage is another measurement and I will use a voltmeter to measure this. I will measure the current using an ammeter. The cross-sectional of the wires I use will also have to be measured and I will do this using a micrometer.
When measuring the voltage and the current I will repeat the circuit three times so that I can get a result as accurate as possible. If I do not have enough time I will try at least to repeat the circuit twice then at least I will have a fairly more accurate result than just doing the circuit only once. I will also average out the voltage and the amps when I have completed the experiment as this may make it easier to draw a graph or to see a pattern more easily.
Prediction
In the wire there are three electrons which carry the current. They accelerate towards the positive; they collide with the metal atom. If the area increases more electrons can flow, so there is more current therefore less resistance; for example water in pipes.
From this I will expect to find from the experiment that the bigger the diameter the more electrons that can pass through it. Therefore I think that when the diameter increases the resistance will decrease. I think this because more electrons will be able to go through the wire with fewer collisions as there is more space for the electrons to travel through.
Background
I got all this information that has been included in my prediction from my notes in class and my textbook.
I decided to do a trial run before doing the actual experiment to make sure that the experiment would go right first time without any problems.
These are the results from the trial run:
In the trial run the length of the wire was 50 cm so this is the length that I have decided to use in my proper experiment. I have also decided to use the voltage of 6V on the power pack as this gave the best results; the current is not too high that it will melt the wire and not too high that the results will not give a very good conclusion. I have also decided to use all of the lengths of wire that there are between 0.15 cm and 0.57cm.
Graph Analysis
I have found from my graph that as the area increases the resistance decreases. The shape of my line of best fit is a curve. The rate of change goes fast at first on the graph but then starts to slow down. This is because the diameter of the wire gets not that much wider than the one before at first, but then it starts to get wider with each different wire. My first graph suggests that I should draw another graph to find out if the resistance is in anyway inversely proportional to the area. So for my second graph I will do resistance against 1/area.
From my second graph I found that my line of best fit is a straight line. This tells me that the resistance is inversely proportional to the cross-sectional area.
R 1/A
R= k/A
K= gradient
The second graph shows that as the 1/Area increases so does the resistance. The gradient of my line of best fit is 0.15. As the gradient= k, for constantan of 0.5m; k= 0.15Ωmm².
So R= 0.15/Area
Conclusion
I have concluded that as the cross-sectional increases the resistance decreases. I have also found that the resistance is inversely proportional to the area. The curve graph shows me that the resistance decreases as the area increases. The straight graph shows me that resistance is inversely proportional to the area. As I explained in my prediction the electrons carrying the current in the wire are accelerating to the positive. They collide with the metal atoms which mean they lose energy. Losing energy means that there is more resistance. So when the area increases there is more space for the electrons to get through so they don’t lose as much energy, therefore there is less resistance.
Accuracy
I think that the results from my investigation were relatively accurate. I used mostly accurate equipment to get the best results possible. I used a micrometer to work out the diameter of the wire. This piece of equipment was very precise and gave me the diameters I was looking for. For measuring the voltage I used a voltmeter, this was pretty accurate as it gave me the voltage to 4 significant figures. To measure the current I used an ammeter which was also an accurate piece of equipment because it gave me readings to two decimal places. All of these pieces of equipment were really easy to use which gave me an even better chance of getting good results.
In my results I did not seem to get any anomalies at all. There were none in the results table or any in the graph. I did three repeats for the recordings of each wire and I did not need to do any extras.
Reliability
I think that I had enough results to come up with a good graph and there were no gaps in the results either. There was also just enough of a good range to get fine results. Although, I might have added extra diameters in the higher range for instance in between 0.45 and 0.57. There is also a clear line of best fit.
Conclusion
The accuracy of the results helped me to get a good conclusion. If the accuracy had not been that good then the results would have been terrible and so I would not have been able to get a good conclusion from them. The reliability of the results was also an important factor of getting a good conclusion. If the results had not been reliable then I might have come to the wrong conclusion thinking that the results were reliable when they were not. The accuracy and the reliability of the results helped a great deal for me to get an accurate and reliable conclusion.
Improvements
- For the first improvement I would use a new power pack so that it would give out the voltage I wanted. Not like the one I used in the experiment which was at least 3 volts under what I wanted it to be.
- I would also use wire that had not been wrapped up as when I tried to measure the length it was right on the exact length.
Extension
For further investigation next time I would change the length. From that experiment I would be able to find out whether there was less or more resistance with the different lengths of wire. I could also investigate changing the material of the wire which would give me an idea of what material gives the most or least resistance. Finally I could investigate the temperature and this would tell me if there was less or more resistance with hot or warm temperatures
Overall I think that the experiment was a good success and I found out a lot from it.
