Resistance of a Wire
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Resistance of a Wire Plan Aim To find out how length affects the resistance of a wire. Introduction In this investigation I will be looking at the effect length has to resistance in a wire. The wire I will be using is Nichrome Wire an I will be discussing on what resistance is, what affects resistance an how it can be controlled Background Information All things are made up of atoms and are made up of three ions, protons electrons and neutrons. Protons are positively charged, and are found in the nucleus of an atom along with neutrons that have no charge. Electrons are found in rings surrounding the nucleus of an atom. The electrons on the outer most rings in the atoms can sometimes become loose in some materials, eventually splitting into single free electrons. These electrons can move around freely, passing into the next atom and moving in random directions. Voltage is the measure of the electrical status or potential between two points. Voltage causes all these free electrons that are moving around in random directions to form a line and flow in one direction. Voltage can be measured by a voltmeter and in the unit of volts (V) When the flow of electrons is formed, it can pass through materials that will allow it to. When the flow of electrons passes through a material, it is referred to as current. There are two types of current, direct and alternating. Direct current is when the charges in the flow of electrons can only move in one direction whereas in alternating current, the charges can move in more than one direction. Current can also be measured by an ammeter and in the units of amps (I). = Direction of charges When the flows of electrons move through a material easily, the material is called an electrical conductor. Wires are very good electrical conductors and that is the reason they are used in electrical appliances.
This way I could prevent any faults from occurring and make my results more accurate. Length (cm) Voltage (v) Current (A) Resistance (?) 10cm 2.43 2.74 0.89 20cm 2.8 1.72 1.67 30cm 2.96 1.27 2.33 40cm 3.06 0.99 3.09 50cm 3.12 0.79 3.95 60cm 3.17 0.69 4.59 70cm 3.22 0.6 5.37 80cm 3.25 0.52 6.25 90cm 3.25 0.48 6.77 100cm 3.28 0.44 7.45 Actual Results When I had taken down all of my readings, I created a table, displaying all the required information. Length (cm) Experiment 1 Experiment 2 Average (ohms) Voltage (v) Current (A) Resistance (ohms) Voltage (v) Current (a) Resistance (?) 10cm 2.44 2.88 0.85 2.44 2.92 0.84 0.85 20cm 2.83 1.73 1.64 2.81 1.82 1.54 1.59 30cm 3.01 1.27 2.37 2.93 1.24 2.36 2.37 40cm 3.08 0.98 3.14 3.09 1.01 3.1 3.12 50cm 3.16 0.79 4 3.15 0.81 3.84 3.92 60cm 3.21 0.68 4.72 3.19 0.69 4.62 4.67 70cm 3.23 0.6 5.38 3.24 0.6 5.4 5.39 80cm 3.26 0.52 6.27 3.26 0.52 6.4 6.34 90cm 3.28 0.47 6.98 3.29 0.47 6.9 6.94 100cm 3.33 0.43 7.74 3.31 0.43 7.7 7.72 The experiment was completed twice for optimum accuracy within my limitations. Also the average and all the results were rounded to two decimal places as this inserted a common denominator. Analysis Findings After having completed the experiment and analysing the readings, I can confidently state that the resistance of a Nichrome wire increases, as the length increases. This is due to the collisions between metallic atoms and the electrons in the current. Also as the resistance increases, the current decreases at an equal rate. The movement of free electrons together all flowing in one direction make current. The vibration of the fixed, metallic atoms within the wire creates an opposition for the free electrons. If there is more resistance this means that the free electrons are having a stronger force opposing them.
Percentage Difference (%) 10cm 0.8 0.8 0 0 20cm 1.6 1.6 0 0 40cm 3.1 3.2 0.1 3 80cm 6.3 6.4 0.1 2 Length (Cm) Resistance (?) Predicted Results (?) Difference (?) Percentage Difference (%) 10cm 0.8 0.8 0 0 20cm 1.5 1.6 0.1 6 40cm 3.1 3.2 0.1 3 80cm 6.4 6.4 0 0 The percentages were rounded up to the nearest whole percent. As you can clearly see the differences are very minimal and are all under 10%. The smaller the percentage difference, the more reliable they are. Conclusion In conclusion to having completed the whole investigation, I conclude that the predictions I made at the start were correct. The resistance did increase as the length increased. This was due to the increase in probable collisions between the metallic atoms and the free electrons that are passing through the wire. The resistance and length did have a directly proportional relationship. As said in the reason for this prediction, if the length of the wire were to double, so would the number of possible interactions, which would double the resistance. This would be the same if the length were to triple or quadruple. I feel that the investigation was a success in most ways but it did have minute faults that could have been avoided with more equipment. Such anomalous results could have been prevented and if I had to do the same experiment and investigation again, there are some things that I would take into consideration that I may have paid little attention to the first time. The preliminary test was to familiarise myself with the circuit and procedure but not all the sources of error in the circuit had arisen in the preliminary experiment. This is the reason they were not prevented after the when the actual experiment was to be done. On an overall feeling about the experiment, I feel that it was an accomplishment in research over resistance and the results derived from the test were reliable and can be used in evidence when proving that length does affect resistance in Nichrome wire. - 1 -
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