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Wire and Resistance Investigation

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Physics Double award science Coursework Simon Rabin


The longer the wire the greater the resistance, therefore if I double the length of the wire I am doubling the resistance

What is resistance?

Electricity is conducted through a conductor, for the benefit of this experiment wire, by means of free electrons. The amount of free electrons vary depending on the material but the more free electrons there are the better the conductor is. For example gold has more free electrons than Iron so therefore it is a better conductor. The free electrons are given energy and then move around and collide with other free electrons, this is how electricity is conducted. Resistance is the result of energy lost as heat. It involves collisions between the free electrons and the fixed particles of the metal, other free electrons and impurities.


I must measure and record the voltage and the current of a circuit with 9 different lengths of wire. Firstly I will attach a piece of wire to a ruler stick and pull it as tight as possible.

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Increasing temperature of wire

All of the above must be taken into account in order for it to be a fair test as it is important that the results are accurate.


The longer my wire is the greater the resistance, because the more wire there is then the more atoms there are and therefore there will be more collisions resulting in more energy being lost as heat.

Preliminary work

In a lesson previous to my experiment I set up a circuit which included a variable resistor. A variable resistor is used to shorten and lengthen the amount of wire used in a circuit. I found that when I shortened the wire with the resistor the resistance was 8 Ohms, when the resistor was in the middle the resistance was 12 Ohms and when the wire was at its longest the resistance was 20 Ohms. This helped me come to my hypothesis as it shows that the longer the wire the greater the resistance. Although the main reason for my preliminary work was to find out the best voltage to do the experiment with.

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Although the experiment itself wasn’t as accurate as it could have been it was easy to conduct and my results are fairly accurate. Certain methods used in the experiment caused it not to be as accurate as it could of been for example:

  • The end of a crocodile clip is about 3mm wide
  • It was impossible with the equipment that was available to get the wire completely straight on the metre ruler.
  • After a while the wire got very hot and therefore effected the resistance.

Improvements that could be made are:

  • The wire to be properly stuck to the ruler stick
  • Clips that make 100% contact with the wire used
  • And a new peice of wire used for every recording so that it doesn’t get hot and affect the resistance.

The two graphs that show my results prove that the resistance is greater when the length of the wire is greater and that the resistance is directly proportional to the length of the wire. Therefore my two graphs fit my prediction and preliminary work.

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