The electrical resistance of rires Essay Example for Free

The electrical resistance of rires Essay In this investigation I will be looking at the resistance of wires to an electrical current and determining the factors that affect the resistance of a wire. There are five main factors that affect the resistance of a piece of wire. These are as follows: 1) The material that the wire is made of. 2) The length of the wire 3) The thickness (or diameter) of the wire. 4) The temperature of the wire. 5) Voltage of the circuit. However, in my investigation I will only be looking at two different factors that affect the resistance of the wire. These two factors are length of the wire and thickness of the wire. Apparatus For this investigation I will need several pieces of apparatus, these are as follows: 1) A ruler (to measure the length of the piece of wire that is being used). 2) Wires (to connect the circuit together) 3) A multimeter (to measure the resistance of the wire) 4) A role of Constantine wire. Method In this investigation I will do as follows: As I will be investigating one variable at a time, I will need to keep the other variables constant. When measuring the length I will always use the same material: Constantan wire. Also I will make sure that the wire does not get hot by not measuring any less than 10cm. Also, I will always use the same thickness wire, 32SWG (standard gauge). However, when I am looking at the factor of thickness I will make sure that the wire does not get hot, that the wire is Constantan wire and that the wire is always a set length, 50cm long. I need to keep the variables that I am not looking at or measuring the same at all times because of the fact that if I have two variables varying at the same time then I will not know which variable affected my results or how much it affected them. Because of this I will only be looking at one factor at a time to make sure that my results are as accurate and true as possible. In both factors I will always be using the same multimeter throughout. I will look at the factor of length first. In this I will keep the variables that I am not investigating the same so as to make it a fair test. Then, I will set up my circuit (See below this paragraph) Then, I will take readings of the resistance with the wire at a length of 10cm using the multimeter set at 200?. Multimeter Ruler Constantan wire I will then repeat the experiment with a 20cm piece of wire and measure the resistance of that. I will do this with pieces of wire 10cm, 20cm, 30cm, 40cm, 50cm, 60cm, 70cm, 80cm, 90cm and 100cm long to get a good range of readings and results. When I will measure the affect that thickness has on the resistance of a piece of wire I will do the experiment with 20, 24, 26, 28, 30, 32, 34 and 38SWG thickness of Constantan wire. I will also repeat each test for both variables 3 times and gat an average to make it a fair test. Predictions My hypothesis for the investigation concerning the length is this: As the wire gets longer, the resistance will increase. This will be in direct proportion and will produce a straight-line graph. I think that this will occur: As the electrons move through the wire, they collide into ions. This makes the resistor hotter and is what causes the resistance. The longer the piece of wire, the more ions for the electrons to collide into, therefore the resistance will increase. The graph that I will plot should be a straight-line graph; according to OHMS LAW. The graph should look like this: Ohms law states that for some conductors, the current flowing is proportional to the voltage, provided that the temperature does not change. For example, if you double your length of wire, then the resistance will also double. My prediction for the other factor that I am going to investigate, thickness, is this: As the thickness of the wire increases, the resistance will decrease. This is inverse proportion. I predict that this will also give a straight-line graph but going downwards instead of upwards. The graph should look like this: I think that this will happen because of the fact that the thicker the wire, the greater the number of electrons that will be able to travel through it at one time. Results Testing the thickness. Using a 50 cm long piece of Constantan wire: SWG Equivalent in mm 1st attempt 2nd attempt 3rd attempt AverageThe Graphs Testing the Thickness using 50cm Constantan wire Testing the Length using 32SWG Constantan Wire Analyzing the Data Length From my results and my graphs I can see that as the length of the wire increases, the resistance of the wire also increases. As my graphs gave a straight line at all times and points, I can say that the resistance is directly proportional to the length of the wire. Because the resistance is directly proportional to the length, I can say that if the length is 10cm and the resistance is 0. 5Ohms, when the length of the wire is 20cm, the resistance should be 1. 0Ohms. These results support my prediction. An odd occurrence is that the line does not pass through the origin (0,0). I believe this is because of slight errors in the readings whish make the line pass just above the origin. Thickness From my results, I can see that as the millimeters increase the resistance decreases. Therefore we can say that the thickness is inversely proportional to the resistance, as the thickness increases the resistance decreases. This was as I expected. However, in my prediction, I predicted that the graph would be a straight line and in my actual results my graph turned out to be a curve. Because of the fact that the graph is inverse proportion, I can say that if you double the SWG then you will half the resistance. My results support part of my prediction (that the resistance will be inversely proportional to the thickness) but not the part that states that the graph will be a straight-line graph. On this graph I used millimeters instead of SWG because it makes it easier to see the relationship between the resistance an the thickness of the wire. Evaluation In my investigation, I only investigated two of the different factors that affect the resistance of a wire. However, there are more than that, as I stated earlier on in my plan. There are also the factors of Material, Temperature and Voltage to be investigated. I could have extended my investigation further by also looking into and testing these other 3 factors. However, I only investigated 2 factors, the length and thickness. Length I think that overall, my results were fairly accurate but definitely could have been more accurate. For 32SWG, the results were a little inaccurate but nevertheless were accurate enough to produce a good directly proportional straight-line graph. I could have made more accurate results and a more varied set of results by doing the experiment at more than just 32SWG. This would have given more varied results at different thicknesses. I could have made my results more accurate by doing the experiment more than 3 times (perhaps 5 times) and taken the average of each set of results. This would have given me more accurate results. Inaccuracy in the results (like in the first attempt on length at 40cm) may have been due to the fact that the equipment used may not have been working properly or plain human fault. Also, when measuring the length of wire to be tested, it is possible that I may have slightly misread the length on the ruler by a couple of millimeters because of kinks and twists in the wire making it nearly impossible to get a perfectly straight piece of wire. This may have caused slightly inaccurate results. Thickness My results for testing the thickness were, on the whole, quite accurate with the exception of minor mistakes. This could have been due to an inaccurate length of wire, a temperature change or an inaccurate reading. However, the over all results produced a good smooth inversely proportional curve. If I were to conduct this experiment again I would have used more accurate equipment and tested more lengths at more SWGs than I did to give a more varied set of results. 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.