Investigation on the resistance of nichrome wire Essay
Investigation on the resistance of nichrome wire
If a length of a wire contains a certain number of atoms when that length is increased the number of atoms will also be increased. I have come to this conclusion because at 0mm-100mm the resistance of the wire is 1. 0 ohm if I look at 0mm-600mm the resistance is 4. 7ohms. The shape of my graph is in a straight line. The rate of change is the same as it goes up. I know this because the line of best fit is straight and goes up by about the same amount each time and can join most my points up apart from four, which does not fit (this could be down to an error in the measurement of the wire or a temperature rise).
Although by taking more than one result then calculating the average increased the reliability of my results and meant that in my graph I had no major anomalies. I got these results because if the resistance of wire is 1. 0ohm whichever part of the wire you pick where the distance between the crocodile clips is 100mm, it should go up by the same amount each time if you increase the length from the start by 100mm. This is why I think that it goes up in a straight line, because the amount of resistance goes up the same each time.
Also “if you have a longer piece of wire there are more atoms and electrons, which can collide to create resistance than in a shorter piece of wire, where there are less atoms and electrons”(1). This is because if you double the length of wire there would be double the amount of electrons and atoms colliding causing resistance. That is why the longer the length of Nichrome wire, the bigger the amount of resistance. I predicted that the longer the wire the more resistance so my prediction was right and I support my theory.
I also predicted that the line would be a straight line and it is, therefore my conclusion supports my prediction. I have not deducted the resistances of the leads because if I did not measure it, the graph line does not go through the origin because of this resistance being included. Where the line crosses the y-axis is the resistance of the clips and leads. If the wires diameter is increased the resistance will decrease. This is due to the increase in space for the electrons to travel through. “Because of this increased space between the atoms, there should be fewer collision.
If the cross-sectional area of the wire were greater, the resistance would be less because more current will be able to flow through the wire. “(1) Temperature has an affect on the experiment as the resistance increases with temperature. If the wire is heated up the atoms in the wire will start to vibrate because of their increase in energy. This causes more collisions between the electrons and the atoms as the atoms are moving into the path of the electrons. This increase in collisions means that there will be an increase in resistance.
The type of material will affect the amount of free electrons, which are able to flow through the wire. The number of electrons depends on the amount of electrons in the outer energy shell of the atoms, so if there are more or larger atoms then there must be more electrons available. “If the material has a high number of atoms there will be high number of electrons causing a lower resistance because of the increase in the number of electrons. “(1) Also if the atoms in the material are closely packed then the electrons will have more frequent collisions and the resistance will increase.
The reason that the length is proportional to the resistance is to do with free electrons. The free electrons constantly flow around the circuit, as fast as they can. The ions in the circuit though, get in their way, and the electrons and ions collide causing resistance. This is what causes resistance. “By increasing the length of the wire, we are adding more ions to the circuit therefore increasing the chance that they will collide. “(1) Evaluation Method I managed to set up the apparatus as accurately as possible. I used all the same apparatus for each experiment, I did this so that it was fair and made my results accurate.
During my experiment I have noticed several modifications I could make to improve on my investigation if I was to repeat it. The first modification I would make would be to use pointers instead of crocodile clips I would do this because pointers could be placed more accurately. I found it difficult to attach the crocodile clips onto the wire. I found this difficult because I had sellotaped the wire down to the ruler to keep it in place yet this did make making accurate measurements hard. As well as making these modifications I would also improve my Investigation by testing the same wire but different widths of that wire.
I would do this to expand on my Investigation. My results were quite accurate apart from four, which I found, did not match. It did not match because the others went up by 0. 7ohms but four is not the same because it went up by 0. 6ohms or 0. 8ohms. This is not really a big difference but it does mean that the experiment was not as accurate as it could have been. My anomalies could be down to many things but I think the crocodile clips might not have been put on straight instead they could have been placed on a tilt, this would mean that the distances in between the clips were incorrect.
All of the averages of the three experiment were either totally accurate or just 0. 1ohm out. They were all very close which means they are accurate. The only ones that have a bigger difference of 0. 2ohms between the are experiment three for the 0mm to 600mm which is 4. 8ohms and the others were 4. 6ohms and the experiment one for the 0mm to 900mm, which is 6. 9ohms and the others are 6. 7ohms. These were not anything to panic about because they averaged out correctly and gave no major anomalies. I think my results are still reliable. To also improve on my results I would use a digital voltmeter instead of an analogue meter.
I would do this because “a digital voltmeter is a lot more accurate than an analogue because if the needle in the analogue voltmeter is bent then the readings given off will be false whereas a digital voltmeter does not rely on a needle or any other manual movements” (1). Graph On my graph the points I have plotted are all joined apart from four. This means my line of best fit is accurate and that I have no major anomalies. Therefore my conclusion is correct because the graph should go up by almost the same each time. I spotted anomalies when I was looking at my results table because all of the resistances go up by 0.
7ohms but four goes up by either 0. 6ohms or 0. 8ohms. I think I got those anomalies because of a wrong measurement when I was attaching the crocodile clip to the wire. I probably just made the increasing gap bigger than it should have been because the resistance between the two points were more than normal 0. 7ohms. If I had time the additional experiments which I would have carried out to be sure of my graph results would be longer length of Nichrome wire, to see if the graph would carry on in a straight line and increase by the same resistance each time and the resistance of the clips and leads would have been less significant.
I do not think there is another way to investigate the variable I did apart from changing the apparatus and using a power pack, digital voltmeter and ammeter instead of using a multimeter. Things, which could affect the end result of my investigation, need investigating. Things that could affect my final results would be rusty old crocodile clips so I would have to test them to make sure they gave the correct resistance. I could do this by attaching two crocodile clips together in a circuit with a multimeter and if the resistance were different from 0. 3ohms I would know that they are not giving me the correct resistance.
I know this because in my preliminary experiment I did the same but with clean crocodile clips and they gave me a resistance of 0. 3ohms. If I were using a power pack I would also need to investigate the heating affect. I would have to use a thermometer to check the temperature of the wire. Lucy Kennington C2 1 G. C. S. E Science Coursework 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 Arkansas System
Type of paper: Thesis/Dissertation Chapter
Date: 13 October 2017
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