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Investigation into the factors which affect the resistance of a wire.

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Investigation into the factors which affect the resistance of a wire.


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


In this investigation, I will find out the relationship between the length of wire and the resistance across it, according to the formula V=I x R. In Ohm’s Law, resistance can be calculated by dividing the voltage by the current. The investigation that is being carried out shows how the resistance (founded by Ohm and recorded in Ohm’s laws) is affected by lengths of a wire. Physists believe in two main theories: the longer the wire the more the resistance, the thinner the wire the more resistance.

I will be investigating the first of the two theories and justify my hypothesis.  http://www.physics.smu.edu/~scalise/emmanual/ohm/lab.html

Hypothesis:                                                                                                                                                         The longer the wire in the circuit, the higher the resistance will be.

Justification of hypotheses:

I have based my hypothesis on many sources, such as internet based websites and books. Each source states that the longer the wire the more the resistance. This is mainly due to the electron movement. Simply, the electrons in the circuit create the current. These are the particles that move through a circuit. However, every wire has some resistance that is already present. In the copper wire that I am investigating on, the resistance is the copper ions.

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· 5 Crocodile Clips                                · 1 Voltmeter Shunt                                    

· 1 Ammeter                                        · 1 Ammeter Shunt

· 1 Voltmeter                                      image06.png


Method:                                                                                                                                                                       In order to complete this experiment, the length of a wire will be changed then its resistance recorded. This will be done a number of times, in order to make the investigation a fair test.  The results of a minimum of four different readings will be collected, as repeating the experiment makes it more accurate and reliable.  The following steps will be completed:                                                                                                                                                                   · Firstly, the circuit will be set in series, with the voltmeter in parallel. image07.png

· Secondly, the current and voltage will be recorded with the wire at 5cm. With the wire at this length, the results will be recorded four different times, so that the experiment is fair.  


· Next, the crocodile clip will be moved up in intervals of 5cm, and each time the result recorded four times.                                                                                                                image09.png

· The results will be recorded from 5cm to 35cm, each one four different times. Once a result is recorded, the power pack must be switched off before recording the next result. This is to reduce inaccuracies and to make the test a fair one.

I have decided to investigate how the length of a wire affects its resistance because other factors such as temperature are hard to control or vary. There are not a large enough range of materials to investigate how materials affect the resistance of a wire.

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· I also made sure I used the same wire and not a different one, incase this may change the results slightly.

· Another thing I did to make sure this was a fair test was to switch the power pack on and off very quickly, so that the wire didn’t get too hot and affect the results.

Therefore, none of my results appeared to be anomalous.

To improve my experiment, I could have taken more care over the temperature at which the wire was kept. To do this I would have to switch the power pack on and off at exactly the same time and also to wait for the wire to cool for the same period of time.

If I were to do this experiment again, I would make sure that the preliminary results included no anomalous results, and this would enable to compare the two experiments together. . From this I could be able to compare the similarities of the two experiments rather than differences. It would also be easier for me to draw quick conclusions.

Overall, I feel that I have completed this experiment quite well. My results are reliable and accurate and so I can conclude that the longer the wire, the larger its resistance.





Class work book & Text book.

Naaila Haq        10g2        Physics Coursework

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