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Investigate the factors that affect the resistance of a wire.

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Investigate the factors that affect the resistance of a wire


In this investigation I will be setting out to find the relationship between the length of a peace of wire and its resistance. The first part of this investigation is the planning; here I will say what I am going to do and why I might by doing it. I will also write up some scientific evidence that will explain my prediction for the final experiment.

    The next stage will be the obtaining evidence. In this part of my investigation I will be working through my method whilst doing the actual experiment. I will collect my results and then put them in a table.

   The third section is the analysis of results, which includes a graph in which I plot all the points I have obtained in the actual experiment from my table. This section will also include a conclusion where I search for any patterns that may occur in my results and try to explain them and also whether it is what I expected linked with my prediction.

   The last section will be my evaluation where I look at any anomalous results, and state how I could improve my accuracy and obtain better results. This will include improvements and anything else I could investigate to discuss what factors may affect the resistance of a wire.

Key Factors

  • The temperature of the wire
  • The thickness of the wire
  • The length of the wire

Independent variable

An independent variable is the one factor I am planning to change.

...read more.

















Trial experiment 2 (0.55mm wire)

Length (cm)

Resistance 1



Average (1.d.p)

Actual resistance
















After conducting my trial I have decided to use the wire with the width of 0.3mm, as this was the one out of the two that gave me the greatest range of results. From this trial I have decided that I am going to use a range from 0-55cms of wire.

In my actual experiment I will not use the same method as I just did in my trial. I don’t believe my trial was accurate enough as I didn’t use ohms law properly. Ohms law states that: -

At a given temperature (if constant), the resistance is proportional to the wires length, and inversely proportional to its cross sectional area.

However the temperature didn’t stay constant in fact it heated up a lot. This is all because 6V were going through the wire so it heated up. The resistance is increased when it is heated up because the atoms or particles in the wire more around a lot more and vibrate causing more collisions because the heat is giving them energy.


This is this apparatus I will be using for my experiment: -

1 multimeter (set as ohmmeter)

2 cables

2 crocodile clips

1m of 0.3mm thick wire on plank of wood

1 metre long ruler

1 micrometer

Diagram of apparatus


  1. Set up apparatus. Connect the cables the appropriate way from the ohmmeter. Connect crocodile clips to the ends of the wire.
...read more.



Overall I think that my accuracy throughout the experiment was to the best I could possibly do. I checked the width of the wire, I did the experiment on the same day and I even checked the current in the circuit itself before connecting it to the wire. My repeat readings were also very good I thought and I did not get any bizarre results.

   I think I could have been more accurate with the measuring of the wire, but I will discuss this further in my improvements.


First of all if I were going to change anything I would change the range of my data. As I measured for 0-55 I got 11 readings (which I thought was very reasonable) if I had more time I may have been able to do more. But I feel in the hours lesson this was reasonable.

   I could have also gone up in smaller intervals to give more readings. This would be more accurate and may have further reduced any anomalous results.

Further work

I have only looked at one factor in this investigation, the length of wire. If I were to do this investigation again I could change the thickness of the wire rather than the length. I would need at least 8 different thickness wires going up in equal thicknesses.

I were to carry forward this investigation my controlled variables would be length of the wire and temperature of the wire. I would also have to keep the type of wire constant too. My prediction for this experiment would be that the thicker the wire the lower the resistance.

The controlled variable would again be the resistance as it should be less, as the wire gets thicker.

...read more.

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