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Investigate how the resistance of a wire is affected by the length of the wire.

Extracts from this document...

Introduction

Physics Coursework

Resistance of a Wire

Resistance of a Wire

Aim: To investigate how the resistance of a wire is affected by the length of the wire.

Secondary Evidence

What is resistance?

Electricity is conducted through a conductor, in this case wire, by means of free electrons. The number of free electrons depends on the material and more free electrons means a better conductor, i.e. it has less resistance. For example, gold has more free electrons than iron and, as a result, it is a better conductor. The free electrons are given energy and as a result move and collide with neighbouring free electrons. This happens across the length of the wire and thus electricity is conducted. Resistance is the result of energy loss as heat. It involves collisions between the free electrons and the fixed particles of the metal, other free electrons and impurities. These collisions convert some of the energy that the free electrons are carrying into heat.

How is it measured?

Middle

0.69

0.58

0.68

0.57

45cm

0.75

0.57

0.78

0.57

0.75

0.56

50cm

0.81

0.56

0.83

0.55

0.82

0.55

 0.91 v I v I v I 5cm 0.08 0.7 0.09 0.7 0.08 0.7 10cm 0.14 0.69 0.14 0.69 0.14 0.69 15cm 0.2 0.68 0.21 0.68 0.2 0.68 20cm 0.26 0.67 0.27 0.67 0.27 0.67 25cm 0.3 0.66 0.3 0.66 0.3 0.66 30cm 0.35 0.65 0.36 0.65 0.35 0.65 35cm 0.4 0.64 0.4 0.64 0.42 0.64 40cm 0.45 0.63 0.44 0.63 0.47 0.63 45cm 0.51 0.62 0.51 0.62 0.53 0.62 50cm 0.54 0.61 0.54 0.61 0.56 0.61
 1.22 v I v I v I 5cm 0.06 0.71 0.05 0.72 0.05 0.73 10cm 0.08 0.71 0.07 0.71 0.06 0.72 15cm 0.1 0.7 0.11 0.71 0.1 0.71 20cm 0.13 0.69 0.13 0.7 0.14 0.71 25cm 0.18 0.68 0.17 0.7 0.17 0.7 30cm 0.21 0.67 0.24 0.7 0.25 0.69 35cm 0.23 0.67 0.27 0.69 0.27 0.68 40cm 0.26 0.67 0.3 0.68 0.29 0.67 45cm 0.28 0.67 0.32 0.68 0.31 0.66 50cm 0.33 0.66 0.34 0.67 0.34 0.66

Conclusion

Evaluation section. The reason why this is the likely explanation is because resistance is known to be inversely proportional to the cross-sectional area.

Evaluation

The results of this experiment would be difficult to improve on because they are reasonably accurate, and there were no anomalous results. If I were to do this experiment again I would take a much wider range of readings and more readings so that a more accurate average can be taken. I would also take the reading from the ammeter more than once so I could get an average. This would make the experiment more accurate. I would use a longer length of wire to see if the graph of resistance changes from a straight line with a much longer length of wire.
I would also investigate another factor, such as diameter of the wire. I predict that if I did investigate this, when I increased the diameter the resistance would decrease. I would also do the experiments under different conditions such as temperature to see the difference this makes to resistance.

Micheal Gridley 11Bd 10/05/2007

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1. Investigate how the resistance of a wire is affected by the length of the ...

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