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Investigating how the Length of a wire Affects the Resistance.

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Investigating how the Length of a wire Affects the Resistance

Planning –

There are four factors that affect the resistance of a wire.

They are: Area, Length, Material and Temperature

I am investigating length. I am doing this because length is the most practical one to do and I won’t have to change the wire. There is no point doing area because I would have to change the wire and keep the length the same. The same goes for material and temperature. I am hoping to achieve how resistance affects a piece of wire when the length is changed.

This is a diagram of a circuit:


Here is a diagram of the experiment I am going to set up:


Fair Test –

In this experiment the variables must be controlled. This means I must keep the same type of wire, same material of wire, same cross sectional area and a constant temperature (room temperature).

These factors must be controlled to maintain a fair test.

...read more.


An example of this would be in a 40 cm wire. The electrons would have to travel double the distance if it had to go through a 20 cm wire.

Preliminary Experiment –

The reason for doing a preliminary experiment is to practice for the real experiment and to make any changes in the real experiment if needed. I set the experiment up in exactly the same way, using 2 volts on the power supply. In this preliminary experiment I only recorded the following lengths:

  • 100 cm
  • 70 cm
  • 50 cm
  • 20 cm

I only did one reading for each length in this preliminary experiment as you can see below in the results table.

Length (cm)

Potential Difference




Resistance (R=V/I)

















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My results are at 20 cm 0.89 Ohm’s and at 40 cm the resistance is 1.80Ohm’s which is almost double the size.

The results that I have obtained support my prediction. This is because in the prediction I said that as the wire length increased, the resistance should increase. I also said that the link should be proportional.

These results have shown that it is true.

The line of best fit clearly shows that the results followed the expected pattern very well. The points are very close, if not touching the line.

This shows how the results were directly proportional through out, as the gradient remained the same.

Evaluation –

The results of this experiment would be very difficult to improve on because they are reasonably accurate, and there were no drastically anomalous results.

 If I were to do this experiment again I would take a much wider range of readings and more readings so that an accurate average could be taken.

I would also consider making the wire much longer and taking shorter distances. For example 10 cm, 15 cm, 20 cm, 25 cm, and so on.

...read more.

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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