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Resistance of a Wire

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Introduction

Resistance of a Wire By Steven Hodkin Science Coursework Plan I am going to investigate the effects of changing a piece of wire in a circuit. The type of wire that I will be using is s.w.g. 32. I will see if the length of the wire will make a difference in the resistance of the circuit. In this experiment there are several variables. The ones that I am going to change are the length of the wire and position on the variable resistor. The ones that I will keep the same are the voltage, the current and the heat of the wires. I will work out the resistance by dividing the voltage by the current. Prediction I predict that the longer the length of wire the more resistance there will be. I therefore think that the graphs that my results will generate will look like the one below. The reason that I think the longer the length of wire the more resistance there will be is because the longer the wire the more static metal ions there will be. Therefore the harder it will be for the electrons to move through the wire without hitting the ions. The ions in the metal are fixed ion molecules therefore when the electrons hit them they will rebound. This makes it difficult for the electrons to pass through the wire quickly, therefore the resistance will increase. ...read more.

Middle

Results Length Potential Difference (Volts) Current (Amps) Resistance (Ohms) Average Resistance 20 0.42 0.1 4.2000 4.2892 20 0.47 0.1 4.7000 20 0.56 0.13 4.3077 20 0.57 0.14 4.0714 20 1 0.24 4.1667 40 0.63 0.08 7.8750 8.3177 40 0.81 0.1 8.1000 40 0.94 0.11 8.5455 40 1.11 0.13 8.5385 40 1.45 0.17 8.5294 60 0.81 0.06 13.5000 13.5674 60 0.88 0.06 14.6667 60 1.01 0.08 12.6250 60 1.35 0.1 13.5000 60 1.49 0.11 13.5455 80 1.1 0.06 18.3333 17.4194 80 1.19 0.07 17.0000 80 1.31 0.08 16.3750 80 1.48 0.08 18.5000 80 1.52 0.09 16.8889 100 1.15 0.06 19.1667 20.8202 100 1.24 0.06 20.6667 100 1.4 0.07 20.0000 100 1.55 0.07 22.1429 100 1.77 0.08 22.1250 These are my first set of results and it is clear that as the length of the wire increases so does the resistance. However as the length reaches 100 cm it seems to even out. This could be because it is an anomalous reading. These are my second set of results and again it is clear that as the length of the wire increases so does the resistance. However as the length reaches 40 cm it seems to dip below the average. This could be because there was a power surge in the cells or there was a faulty connection. Most of the results follow the same pattern as the other graphs however the entry at 60 does not conform to the pattern. ...read more.

Conclusion

For example when the wire length is 20 the resistance is 4 and when the length of the wire is doubled to 40 the resistance also doubles to about 8. My prediction states that as the length of wire increases so will the resistance and that this increase is caused because of the addition of more fixed metal ions. When the length of the wire is doubled there are twice as many fixed metal ions as were before therefore the resistance will have increased by roughly half. Evaluation My results prove that my prediction was correct. I realise that there were flaws in my experiment however I think that they would be very hard to eliminate. The flaws that I can see are: * Fluctuations in the power supply * Fluctuations in the heat of the wires and environment * Differences in the distance that the control on the variable resistor is moved ever time I could eliminate these by using a continuous power supply, such as a transformer plugged into a mains socket. I could also eliminate any discrepancies in the distance the controller is moved by measuring the distance instead of estimating. I could also increase the accuracy of my results by doing the experiment more times. I could perform the experiment 10 times with each length of wire this would make the average more precise and it would also make any erroneous results easier to identify. If I had done more experiments it would also have made my graphs more accurate. ?? ?? ?? ?? Steven Hodkin 27/04/2007 1 ...read more.

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