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Resistance of a Wire Investigation

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Resistance of a Wire Investigation


Resistance is measured in Ohms. This is calculated by finding both the current and the potential difference over a test substance. Then by using Ohms Law, you can find the resistance of any material over any distance.

Ohms law is; Resistance (R) = Potential Difference (V)

                                               Current (A)


  • Length of wire
  • Thickness/Diameter of wire
  • Material wire is made from
  • Surface area of wire
  • Number of coils of wire
  • Density of wire
  • Temperature of wire
  • Atmospheric conditions
  • Amount of current flowing through wire
  • Potential Difference flowing through wire
  • Material wire is wrapped around

I have chosen to use the length of wire as my variable. I have chosen this particular one because it is easy to carry out easily without too much chance of error. It is

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is the length of wire as it can be altered easily using a jockey and the results are easy to obtain accurately. The range I have chosen for this experiment is between 0 and 100 centimetres. This is because it can be easily calculated accurately using a metre rule.


  • 1 metre rule
  • 200cm of Nicrome wire SWG 22 (experiment was repeated – i.e. 100cm of wire needed for each experiment)
  • 1 Power supply
  • Copper wires
  • 1 jockey (instrument used to vary the length of wire without cutting it)
  • 1 Ammeter
  • 1 Voltmeter
  • Masking tape


I predict that as the length of the wire increases, the resistance will increase. This is because, as the length of the wire increases, there is less and less room for the particles to vibrate. This means that the current will be resisted more. This is also stated

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How the experiment was made a fair test

  • The experiment was repeated so that the risk of error was greatly decreased
  • Only one variable was used. If more than one variable is used, it is impossible for the experiment to be accurate.
  • The power supply was only switched on for the amount of time it took to read the potential difference value from the voltmeter. This was because if the power supply was left on any longer the Nicrome wire would have heated up, creating a second variable

How the experiment was made safe

  • The Nicrome wire was not allowed to get hot, which could have burned someone if they touched it
  • The current was kept well below the limit of both the ammeter and the voltmeter so that there was no chance of their fuse blowing
  • All bags were kept outside the lab to avoid anyone tripping over and hurting themselves

Daniel Fisher

        The resistance of a wire

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