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Factors that affect the resistance of a wire

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Introduction

There are different factors that affect the resistance of a wire: * Length * Thickness * Temperature * Voltage * Material I am going to do two experiments in this investigation. In experiment one I am going to investigate how the resistance of a wire depends on its length. In experiment two I am going to investigate how the resistance of a wire depends on its thickness. I have chosen to investigate these two factors because they are the easiest to control, so therefore my results can be more accurate. I know that resistance can be calculated with this equation: Resistance (ohms) = voltage (in V) current (in A) Experiment One First a length of wire, made out of copper, which is over a metre long, is cello-taped to a metre rule. One crocodile clip is attached at 0cm and the other crocodile clip is moved up and down the wire to different lengths: 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100cm. I will measure the current using an ammeter and also I will measure the voltage using a voltmeter. Then I can work out the resistance (R = V/I). All the other variables, voltage, thickness, temperature, will be kept constant so that it will be a fair test. Experiment Two The circuit is set up is the same as in experiment one, except I will keep the length of the wire the same, at 50cm, but I will very the thickness of the wire. ...read more.

Middle

So I predict the thicker the wire the more resistance it will have. You can measure the resistance of a wire by using the formula: Resistance = Voltage/Current. Experiment 1 Length (cm) Voltage 1 Voltage 2 Voltage average Amps 1 Amps 2 Amps average Resistance (ohms) 10 0.26 0.28 0.27 2.75 2.88 2.82 0.10 20 1.36 1.20 1.28 2.85 2.77 2.81 0.46 30 1.68 1.58 1.63 2.79 2.71 2.75 0.59 40 2.10 2.16 2.13 2.54 2.57 2.56 0.83 50 2.50 2.66 2.58 2.56 2.60 2.58 1.00 60 2.90 3.01 3.00 2.49 2.58 2.54 1.18 70 3.28 3.33 3.31 2.33 2.28 2.31 1.43 80 3.60 3.59 3.60 2.21 2.25 2.23 1.61 90 3.86 3.84 3.85 2.11 2.55 2.33 1.65 100 6.05 6.00 6.03 3.00 3.00 3.00 2.01 Experiment 2 Diameter (cm) Voltage 1 Voltage 2 Voltage average Amps 1 Amps 2 Amps average Resistance (ohms) 0.36 0.65 0.51 0.58 4.41 4.31 4.36 0.13 0.73 0.35 0.35 0.35 4.73 4.69 4.71 0.07 1.40 0.13 0.19 0.16 5.03 4.99 5.01 0.03 Experiment One The points on my graph of experiment one are a little scattered, but the line of best fit is a straight line which does go through the origin, which means the resistance is directly proportional to the length. So if the length is 50cm, and resistance is 1ohms, when the length doubles to 100cm, the resistance also roughly doubles to 2.01ohms. ...read more.

Conclusion

* The wire might not be completely straight. * It may also be of different thickness throughout the length. Because of these problems, and that I did not have enough results so my experiment was not accurate enough to completely support my prediction. If I were to do this experiment again, I would use newer, more accurate ammeters and voltmeters, a more accurate method of measurement, and take a much wider range of readings, and more readings so that a more accurate average can be taken. I would also investigate other factors, such as temperature, voltage and current, and see how these affect the resistance. I would also do the experiments under different conditions such as temperature and pressure to see if it makes any difference to resistance. But my graph is unclear and hard to see if it is straight line or curve. It would be better if I had more readings, and more points on the graph so I can see a pattern to support or disapprove my prediction. My results do not clearly support my prediction but it does show that the thicker the wire the less resistance there is. To help me with this investigation I used the following: * Complete Physics by Stephen Dople * Letts GCSE Physics * CGP Physics by Richard Parsons * Encyclopaedia - Britannica 99 CD-rom * * * * ...read more.

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