The resistance of a wire Essay
The resistance of a wire
This can be explained because as the length of a wire is increased then the distance the electrons will have to travel in an electric current will increase, so more collisions are likely to occur between them and the ions present. o I also predicted that the resistance of the nichrome wires would be inversely proportional to their cross sectional area. This was proven true since the graph illustrating this shows a straight line descending towards the right side of the graph and ascending towards the left side of the graph.
I can explain this because as the wires cross sectional area is increased the space for the electrons to travel through in an electric current will increase and due to this increased space there should be less collisions between them and the ions. o I also hypothesised that the graphs drawn from the results obtained would resemble the ones that I drew in the PLANNING section. This was the case as can be seen when comparing the graphs I drew with my hypotheses to the ones in this section.
This can be explained because the results obtained in the investigation match the patterns that I predicted they would follow i. e. resistance being directly proportional to the length of the wire and resistance being inversely proportional to the cross sectional area of the wire. o I predicted that not all materials would conduct electricity to the same extent. This was proven true since I discovered something called resistivity by doing some further research, this is the factor in the resistance that takes into account the nature of the material.
I found that all of the metals I used had different resistivities and so conducted electricity to different extents. I can explain this because all of the metals contained copper in different proportions and this element has two free electrons able to flow in an electric current, which is quite high. Copper therefore has a very low resistance and so the metals containing the most copper would have the least resistance out of all the metals used in the investigation and hence the least resistivity. Conclusion
It has been found that the resistance of a wire is directly proportional to its length and inversely proportional to its cross sectional area. This is because as the length of a wire is increased then the distance the electrons have to travel in an electric current increases, so more collisions occur between them and the ions present and as the wires’ cross sectional area is increased the space for the electrons to travel through in an electric current increases and due to this increased space there are less collisions between them and the ions.
It has also been found that the resistivity (this is the factor in the resistance of an element that takes into account the nature of the material) of the copper wire is less than the resistivity of the manganin wire, which is less than the resistivity of the constantan wire and which is less than the resistivity of the nichrome wire. The resistivity of constantan was found to be 51 10-8, the resistivity of manganin was found to be 43 10-8, the resistivity of copper was found to be 1 10-8 and the resistivity of nichrome was found to be 111 10-8.
The best conductor of electricity was therefore the copper wire and the worst conductor was the nichrome wire. EVALUATION Overall, I was pleased with my results. The procedure I used to carry out the experiment seemed to be suitable and good, as my results appeared to be very accurate in respect to my predictions. As can be seen from my graphs, I seem to have only obtained one anomalous result, which appears on graphs 3 and 9 (the ones relating to the copper wire).
To improve the results obtained in this experiment and improve the reliability of the evidence I would take more results so that better, more accurate averages could then be made from them and so more accurate graphs could then be drawn. I would particularly take more readings with the copper wire since this is where I obtained the anomalous result, the reason for this I think is that since its resistance was so low the ammeter and voltmeter fluctuated a lot making it hard to take readings from them.
I think that it is possible to support a firm conclusion with the results obtained in this experiment since all of the points on my graphs either lie on or near the line of best fit (except for my anomalous result) showing that there is a particular relationship between these results and the factors present while obtaining them. During this write up I calculated the resistivities of the metals that I used, I looked in an A-level physics book for the values it gave for the resistivities of those metals in order to compare them with the values I found.
The following are the resistivity values that I found in the book: o The resistivity for constantan is 49 10-8 o The resistivity for manganin is 44 10-8 o The resistivity for copper is 1. 7 10-8 o The resistivity for nichrome is 110 10-8 It can be seen that my resistivity values calculated in the ANALYSIS SECTION are very close to those found in the book. This further emphasises my opinion that my results are accurate enough to draw conclusions. Further Work.
To improve the experiment in order to provide additional and more reliable evidence for a conclusion I would carry out the experiment using additional different metals to see how their resistances would change as their lengths and cross sectional areas were varied. Such examples of these metals could be for example titanium, silver, steel, brass etc… 1 Show preview only The above preview is unformatted text This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.
University/College: University of California
Type of paper: Thesis/Dissertation Chapter
Date: 13 October 2017