Resistance of a Wire Investigation

	 Resistance of a Wire Investigation
Introduction In this investigation I will carry out an experiment to distinguish how the length of a wire, disrupts the behaviour of the resistance. Throughout this investigation I will include my prediction, method, diagram, results and a graph to show the relationship between the length of the wire and the resistance. Remember that resistance occurs when the electrons travelling along the wire collide with the Ions of the wire. Also remember when the resistance is increased, the current will decrease. Resistance is a measure of how hard it is to move the electrons through the wire. The length of the wire also makes a difference in the resistance because, if the length of the wire is increased then the resistance will also increase as the, electrons will have a longer distance to travel and so more collisions will occur. Due to this the length increase should be proportional to the resistance increase. Metals are good conductors of electricity, which is why the big free group of electrons can get away by applying the voltage. Then if an Ion gets in the way of an electron, and the electron collides with the Ion then the electron, will be slowed down and the Ion will also capture some of its energy. The most frequent effects that this will cause would be, a decrease of current and the metal will acquire water. My Hypothesis My prediction in this investigation will be, when you increase the length of the wire, this will lead to the increasing of the resistance and it might also release heat energy. In a longer piece of wire, there would be more Ions for the electrons to collide with and so this would increase the resistance. This is caused, from the distance the electrons have to travel. When the electrons have to travel a further distance, there is more of a risk for them to collide with the Ions. The free electrons collide with the Ions, causing high resistance and low current flow. When the collision occurs, this causes it to release energy. The high flow of energy, which is acquired, makes the wire burn. I also predict that to find the resistance, the formula would be Voltage / Current. I predict that the relationship between the length of the wire, and the resistance of the wire will be directly proportional. This means that as the length of the wire increases, the resistance will increase in equal increments. I expect that this experiment will abide to Ohms Law. This is because, I believe that the temperature will be constant and it will be proportional to the voltage, this will also result in an increase in resistance. Safety Precautions!!! Throughout this experiment, I will make sure that safety is one of my top priorities. I will ensure that none of the wires are frayed and that there is no water near any electric equipment as in all electrical experiments. I will be extremely cautious when measuring the voltage of the wire in case the wire became very hot. I wore goggles as a safety measure although it was not evident, that any sparks etc would be produced in this experiment. Factors affecting resistance The temperature of the wire will have an effect on the resistance because; if the wire is heated up the Ions in the wire will start to vibrate because of their increase in energy. The causes of this are that more collisions between the electrons and the Ions will occur, as the Ions are moving into the path of the electrons. This increase in collisions means that there will be an increase in resistance. Another factor, which could affect this experiment, would be the type of material used, which would be able to affect the amount of free electrons, which are able to flow through the wire. The amount of electrons will be decided by the amount of electrons in the outer energy shell of the atoms, so if there are more or bigger atoms then there must be more electrons accessible. If a 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. If the materials atoms are congested then this will cause the resistance to increase, since there will be more collisions. The length of the wire will effect the resistance, because the longer the wire the greater the resistance. Also the width of the wire can affect the resistance, by decreasing the resistance. Apparatus The apparatus I will have to use in this experiment are as follow: Crocodile Clips, Power Pack, Wires, Voltmeter, Ammeter, Constantine (wire), Metre Ruler and sticky tape. Method The method I used in this practical was first, to connect the voltmeter and ammeter to the power pack. After I had done that I placed the Constantine on the one-meter ruler, and stuck sticky tape to hold it in place. Then I connected one end of the Constantine, to the voltmeter and the other end to the ammeter. Then I started to take readings after each measurement of the Constantine. The measurements started from 10 cm?s and went up to 80 cm?s, and that is where I stopped. Diagram [image] [image] [image] [image][image][image][image][image][image][image][image] A -???????????????????????????- [image] [image] [image][image] V Results -?? First set of results Average Resistance Length of wire Voltage Current Resistance 10 cm 2.52 1.39 2.8 20 cm 2.94 0.52 5.7 30 cm 2.83 0.31 9.13 40 cm 2.99 0.26 11.5 50 cm 3.06 0.22 14 60 cm 3.12 0.18 17.5 70 cm 3.16 0.17 18.6 80 cm 3.51 0.14 25.1 2.3 5.4 8.46 10.5 13.95 15.37 16.3 21.47 Second set of results Length of wire Voltage Current Resistance 10 cm 2.56 1.36 1.8 20 cm 3.00 0.58 5.1 30 cm 2.89 0.37 7.8 40 cm 3.05 0.32 9.5 50 cm 3.06 0.22 13.9 60 cm 3.18 0.24 13.25 70 cm 3.22 0.23 14 80 cm 3.57 0.20 17.85 Above are the results I received from the experiment. The numbers increase evenly which, is an indication of an accurate experiment. I have also added an average results table, which goes up evenly and this shows that it has been an accurate experiment. I found out the average results by adding both resistances from each table at each measurement and then I divided it by two. Fair Testing To ensure that my experiment was as fair as it possibly could be, I had to take care with a lot of things. I made sure the factors that might affect my experiment working well would have been dormant. These were things like temperature, which can affect the wire either by the heat in the room or from the voltage running across the wire. To tackle this problem, I made sure that the power pack was turned off between readings so that the wire did not get hot, and hence affect the reliability of my results at each value. I also tried to limit the amount of human error in my experiment with things such as putting the clips, on the exact lengths and recording the readings on the ammeter and voltmeter correctly. I think that these are important factors because, it can have a negative effect to how accurate and reliable the results were on the whole. It could also leave me with anomalous results that have no reason behind their appearance. In my prediction it also states, that to find the resistance you have to divide the voltage by the current, and my results show that this was the correct formula. Ohm?s Law Ohm?s Law is a set of formulas used in electronics, to calculate an unknown amount of current, voltage or resistance. It was named after the German physicist Georg Simon Ohm. Ohm?s Law says that there is a relationship between these three factors. So if you know two of the values you can easily work out the third one. V= Voltage l= Current R= Resistance V = I x R V I = V / R R = V / I I R Here is a graph showing steady increase in voltage, in a circuit with constant resistance, produces a constant linear rise in current. [image] [image]A steady increase in resistance, in a circuit with constant voltage, produces a progressively weaker current. This is shown on the graph below. Ohm?s law only applies if the temperature is constant, and is also at the same time proportional to the voltage. This means as the temperature increases the resistance will increase aswell. Conclusion In this investigation I found out that the decrease in current is the increase in resistance, this is because the electrons although less of it they collide with the Ions. Or the thickness, or thinness of the Constantine also can affect the amount of collisions in the experiment. I have found out that my prediction was correct. Resistance is caused when the free electrons moving through the wire collide with the Ions making their path through the wire more difficult. So the resistance will also depend on how big the Ions are, if they are small there will be less collisions and if they are large then there will be more collisions. After drawing a Graph to demonstrate the relationship between the length of the wire and the resistance, I found out that the relationship is directly proportional. [image] Resistance of wire In ohm?s Length of wire in cm The graph also illustrates a positive correlation, which means that the results that I received are reliable. This provides proof that when the piece of wire becomes longer, the resistance will also increase in equal increments. Evaluation == I think that this experiment has been a very successful one, as my results supported my prediction. My results were particularly accurate as each result was taken two times at the various voltages, and then I calculated the resistance, which was initiated by using the formula V/C. There were no strange results (anomalies) within my results table, and I think that this was because of the extreme caution and care, which I put into making sure that the experiment, was set up correctly. I tried to measure the wire as accurately as possible and, I made sure that the crocodile clips were situated straight and holding the Constantine in the correct position. I think another one of the reasons why my experiment is quite accurate is because; I tried to measure the wire as accurately as possible. The wire was stretched until it was nearly in a straight line so a bit was overlapping at each end. I have noticed, now that I have finished my investigation, that there are things I could have done to obtain more accurate results. I do not think that doing any more results, in my experiment would have made it any more accurate. I feel that the only way to make it more accurate would be to use a different method, like using a different type of wire, which would most likely have a different effect on the resistance. A further experiment I could do would be to see whether the diameter of the Constantine affects the resistance. This would be fascinating because it is similar to the experiment I have done. I also think that if I had modified the crocodile clips and, instead used pointers this would have given me a more accurate result. This is because the tip of the pointers, have a much smaller area than the crocodile clips, therefore giving an accurate measurement of the length of the wire. This is a further experiment I could have done, to vanish one of the factors, which can affect my experiment. I could have made the temperature factor which can effect my results disappear. When the temperature becomes hot, the Ions in the Constantine start to vibrate, thus developing more collisions and increasing the resistance. To embark upon this difficulty you can, wrap a piece of coil around the Constantine (wire). After I had done that, I would put the Constantine with the coil wrapped around it, into a beaker with water in it. This will stop the resistance from rising, and creating a more precise result. End of Coursework I have also provided a bigger version of my graph on the following page.

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