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To investigate the factors affecting current in a wire.

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To Investigate The Factors Affecting Current In A Wire Introduction The aim of this investigation is to find out the factors that affect current in a wire. Electric current is defined as the rate of flow of electric charge. Variables that may affect the resistance of the wire Every appliance has a resistance. If the resistance is high, the current will be low. If the resistance is low, the current will be high. The variables that can affect the resistance in a wire are: - Cross-sectional area of the wire - Length of the wire - Temperature - The material (resistivity) - Voltage Cross-Sectional Area The thicker the wire is, the lower the resistance, therefore the higher the current (given that all other factors are constant). When a wire is thick, there are more electrons available to carry the current. Free electrons are available in metal (wire), if the metal has a larger cross-sectional area - more electrons will be available. If the wire is thinner, fewer electrons will be available to carry the current. A thick wire has more free electrons and more space. A thin wire has less free electrons and is more 'squashed' together. This means that the electrons are likely to collide more with the metal ions in the wire. Collisions in a metal wire will result in an increase in resistance because the ions from the metal wire will be getting in the way of the flow of electrons. And if there are more collisions, the flow of electrons will be disrupted more. Therefore there'll be less current. R ? 1 a Length of a Wire As the length of the wire increases, the resistance increases. Length is proportional to resistance. And as the resistance increases, the current decreases. As the length of the wire decreases, the resistance decreases hence the current increases (provided that all other factors are kept constant - especially voltage). ...read more.


This was done to make it more convenient when putting on the crocodile clips on the desired locations. So that the wire was completely flat therefore more accurate. Before measuring the current through 10cm of wire, the power pack was left off for a long time. So that the wire could completely cool down. Results The results that were recorded there and then were in a tabular format. After the experiment was completed, these results were transferred to an excel spreadsheet. And the resistance was calculated using the formula: R = V I From these results, two graphs were drawn, for use in the analysis of the investigation. Another extension I could do is maybe investigate how the other variables affect the current in a wire. So if I were testing whether the cross-sectional area affects the current in a wire, I would have to keep all other variables constant. Then I would test different diameters of the same length, material, temperature and voltage. I would expect the current to increase as the cross-sectional area increases. Because increasing that would increase the number of electrons available to carry the current. And also it has more space for the electrons to travel therefore they won't be bumping (colliding with each other) as often. But if it were a thin wire, there would be more frequent collisions between the electrons and the ions. Hence the electrons get slowed down. RADIOACTIVE DECAY CURVES EXPERIMENT Analysing Evidence: Simple Conclusion - From this experiment, I found out that for both isotopes, the activity decays with time. Processing Evidence - From the 2 graphs, I calculated that the half-life for isotope A is approximately 8 minutes and the half-life for isotope B is approximately 1 minute. These are fairly constant over the given time interval. Therefore the half-life is consistent for both isotopes. So I conclude that isotope A is STRONTIUM 93 and isotope B is either STRONTIUM 94 or PROTACTINIUM 234. ...read more.


Because they give the results to a greater degree of accuracy and maybe I could've spotted whether the significant figures affected the outcome of a particular result. For example, 0.2A is the same as 0.16A. A multimeter is less likely to make this assumption. A straighter piece of wire could've been obtained so there would be no corroded or kinked bits in the wire. Then next modification I would make would be to use pointers instead of crocodile clips to attach to the wire. I would do this because pointers are more accurate in measuring the length of the wire. In the experiment, I did not control the room temperature but instead just assumed it was kept constant. So maybe the room temperature could be adjusted so as not to make it very hot, otherwise the resistance of the wire would be greatly affected. I found that I had plenty of time to spare at the end, so maybe next time I could wait longer between readings so as not to get any heat effect at all. These changes would improve the accuracy and reliability of the experiment. Extension Work To further the investigation, I could maybe keep the current constant to measure the heat dissipation. Or I can take an unknown length of wire (that can't be measured because it's so long). So this unknown length of wire will be rolled up like a coil. And I can use this experiment to find the length of it (provided that all other factors are kept constant for a fair test). So what I would do is measure the current through that wire and keep the voltage constant at 2V. Then I can use the formula: Resistance = S x 1 . Length Then using that formula, I can work out K (a constant value). If I'm using the same sort of wire and same thickness (Nickel Chrome 32SWG) then from my earlier calculations, I know that K = 10. So I can work out the length of an unknown nickel chrome 32 SWG wire by the following calculations: Page 1 Varun Sivabalan ...read more.

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