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Resistance Investigation

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Resistance Investigation

There are a few factors, which will affect the resistance of my wire.  These are:

  • The material
  • The length
  • The cross sectional area (thickness)


The independent variable will be the length of my wire.

The controlled variables will be the material and the cross sectional area.

The dependent variable will be the voltage, current and the resistance.

My Plan

I want to see how the length of a wire will affect its resistance. To do this I will have to do an experiment will a type of wire and have specific measurements of length and record the resistance. Here is a small diagram of how the length might affect the resistance.

Short Wire

Longer wire

As you can see the longer the wire is the more collisions there are with the wire atoms.  Therefore this would take the molecules longer to get through the wire and so the resistance is greater.

My formula will be RESISTANCE = VOLTAGE / CURRENT (R = V / I)

My Prediction

I think if the length of the wire is doubled then the resistance will double.

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Safety Precautions

  • Stools under desks
  • Blazer off
  • Long hair tied back
  • Clear table before apparatus is set up
  • Turn off all taps



I see a small pattern in the resistance it does seem to doubles as the length is doubled. The Voltage seems to almost triple in size as the wire length is doubled. The current gets smaller then larger as the length of wire goes up.

Conclusion To Prediction

My prediction was correct when I studied my results carefully I seen that they were not exactly doubling but it was very close so perhaps my results were not accurate enough.    


If the Crocodile clips had have been smaller and had more of a tip to them I could have got my length measurement nearly exact. They could have been measured with a bit more care to the importance of accuracy. There was one result that seemed to be out of place in my results table. It was the 2nd resistance measurement of the 40cm length. It was at 3 but later jumped DOWN to 2.

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Are on the next page on a separate sheet.

Conclusion to prediction

I guessed right again with my predictions as the wire increases in cross sectional area the resistance almost doubles as well. But remember about my problems with the crocodile clips they do tend to slide up and down the wire if you are not careful. So my measurements may not have been exactly accurate due to problems such as this. I think it would be extremely difficult to get completely accurate lengths, so I am happy with my results.

I could not see any really see any results that were out of place in this experiment.

                            Conclusion of Investigation

I conclude that there was a proportional relationship between the wire and the resistance. Usually if one was doubled so would the other. You could use this to predict a length of 80cm or 100cm before carrying out the experiment, or predict a thickness of 38swg or 40swg also. Therefore I could go ahead and predict material, but material is not a measurement as such so it would be hard for there to be any relationship.

      By Janet Campbell

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This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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