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Investigating Factors Which Affect Electrical Resistance

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Investigating Factors Which Affect Electrical Resistance Brief What effect does varying the length of a wire have on its resistance? Background Information Variables involved in this investigation * Length of wire. * Material of wire. * Width of wire. * Starting temperature of wire. All of these affect the; * Resistance of the wire. * Voltage across wire. * Current in circuit. * Temperature of wire. The Length and Width of a Wire 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. However, if the wire width is increased the resistance will decrease. This is because of the increase in the space for the electrons to travel through means less likelihood of the free electrons having collisions and losing energy. Therefore, length of wire is directly proportional to resistance, and width (cross-sectional area) is inversely proportional to resistance. The Material of a Wire The type of material will affect the amount of free electrons which are able to flow through the wire. The more free electrons that there are in a space, the more collisions there will be between them, as the higher the resistance will be as a result. ...read more.


After performing these rough trials, it was decided that a 1V fixed power supply would be used in the proper experiment, as it would provide results for lengths from 30cm up to 100cm without the wire overheating. To increase accuracy, it was also decided to allow the wire to cool between experiments as the wire seemed to be getting hot was noticed at lower lengths and, as mentioned above, an increase in temperature results in an increase in resistance. By allowing the wire to cool between experiments a fair test could be assured. The preliminary experiments also confirmed that the ammeter and voltmeter were compatible with the power supply and that they provided an appropriate degree of accuracy. To ensure that this is a fair test, a fixed power supply will be used, measurements will be taken twice, and the same thickness of wire will be used. A wire will be used that will not overheat at short lengths, which would affect resistance. Safety In order to perform a safe experiment, a low voltage of 1V was chosen so that overheating was minimised. Also, lengths lower than 30cm were will not be tried, which will also help to avoid overheating. Apparatus * Metre rule marked in centimetres to measure the wire being tested to ensure a fair test * a Voltmeter and an Ammeter to measure the voltage and current, and hence find the resistance. ...read more.


My results are the result of taking an average of two experiments, so any inaccurate results that would have made it difficult to see a trend were evened out. If I wanted to increase the degree of accuracy in my results, I could have used more accurate voltmeters and ammeters, and not have rounded my result to 2dp, but I do not think that this very high degree of accuracy is appropriate for this experiment, as the level of accuracy to which my results were taken has provided me with sufficient data to see strong, consistent trends in it. If there are any anomalous results in my investigation which I have not noticed, they could be explained by Ohm's Law. If, at these points (more likely in the lower lengths), the wire was not allowed to cool completely so that the temperature was higher for that measurement, then this could have caused anomalous results. Whilst unlikely, this would cause a higher resistance as explained previously in my background knowledge. If I were to extend this investigation, I would like to see how changing other properties of the wire would affect its current, resistance and temperature. I would like to use experiment with using different metals for the wire, and also with using different widths. Another interesting factor to investigate would be how temperature affects other variables of the wire. ?? ?? ?? ?? 1 Octavia Younger Sc1: Physics ...read more.

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