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measure how the length of the wire affects the resistance in the wire.

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Physics course work.


I am going to do an experiment to measure how the length of the wire affects the resistance in the wire. To ensure that it’s a fair test, the thickness of the wire must be kept the same throughout the entire experiment because when the thickness increases the resistance decreases. The material of the wire has to be kept unchanged, since not all materials have the same resistance
. Temperature similarly affects resistance because as it rises, the resistance in the wire increases. I must use the same wire during the experiment and I have chosen to use constantan as it’s a good conductor of electricity.


The factors that affect the resistance are the length, thickness and material. I will only change the length in my investigation in 20cm spaces, on a 1meter ruler.

Controlled variables:          Temperature (room temperature), Wire material (constantan)

Dependent variable:  Resistance

Independent variables: Length of wire


the apparatus I will be using are:

* Multi-meter                                                                                                                  (I used a multi-meter instead of an ammeter and a voltmeter because the results will be as accurate and quicker to get, and it reads to 2 decimal places)

* Constantan wire (SWG value of

* Meter Ruler

*Masking tape

* 2 connector leads


1)  To start with, connect the two leads in the multi-meter.


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The said above is why I’m keeping the thickness of my wire the same, so to make it a fair test, but  I’ll be changing the length of my wire. I will also keep the material of the wire the same as the resistance will be affected by different metals.

As a wire gets hotter, the resistance increases, which can be explained through the activity of the atoms. When the wire heats up either because of large current flow through a small wire or a high temperature, the resistance increases simply because the nuclei vibrate faster. This means the spaces between neighboring nuclei are decreased and the resistance increases, and oppositely, when a wire is cooled, resistance decreases as there is more gaps between the nuclei as they are vibrating slower.

The resistance and length of a wire are directly proportional to eachother- R    L, which is why I predict that as the length of a wire doubles, so does the resistance.


The length of the wire makes a difference, considering the longer the wire, the more the electrons squash together so that they are capable of passing through the wire.

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In general I think this investigation has went reasonably well. There were 2 anomalous results that slightly stood out on the graph which shows that the experiment wasn’t done to the highest accuracy possible, however the two anomalies almost fitted the trend, showing that I performed the task accurately enough. This was because I used the right equipment and made sure that I took my results as accurately as I could at the time, which is shown by my readings for the three runs, as they are all very alike which shows that the data is dependable. To make my experiment even more reliable I could have used a more stable wire which would have made my measurements more accurate, because the wire may have slackened during the experiment. Therefore to improve my experiment next time I would test the rigidity of the wire throughout my experiment instead at just the beginning. I could have also used another type of wire that had a different thickness, which would consequently get similar results but would progress my experiment.

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