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To discover how length and cross sectional area of a wire affects the resistance of a wire.

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     To discover how length and cross sectional area of a wire affects the resistance of a wire.


      In my opinion, I predict that the resistance of a wire will increase with length. I feel this because the electrons have further to travel therefore it has a higher chance of being terminated/stopped by the atoms. I predict the resistance will decrease when the cross-sectional area is increased. I think this because the electrons will have more space to flow past the atoms.


Fair Test:

     To perform a fair test I will manipulate/test one variable at a time e.g. length.

I will keep the following the same:

  • The power pack
  • The voltmeter
  • The other wires
  • The material the wire is made from
  • The temperature
  • I will keep the cross-sectional area the same when monitoring the length and vice versa  


  • I will set up the apparatus as shown in the diagram above.
  • When a current is flowed through the wire I will record the readings on the ammeter and the voltmeter in to a table.
  • I will then use my results in the formula R=V/I to calculate the resistance of the wire.
  • I will then increase the variable I am analysing and record the data I have mentioned.
  • I will repeat this ten times for length and six times for cross-sectional area.
  • I will try and keep the results reliable by following my fair test above and re-testing my results.
  • By re-testing my result my mistakes should be easy to see (my anomalies).
...read more.


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Cross-sectional Area:

Constant length is 20 cm:

Cross-sectional area (mm )

Current (amps) (I)

Voltage (volts) (V)

...read more.



      The first thing I would have to say is that I definitely don’t think I measured the width of the wire because there are many errors (anomalies) on my graph and in my table. Next time I should take longer to measure them and not rush it as I did. I should also do all of my tests and re-tests at the same time to make sure everything is the same. But there is the problem of the allowance of time to do the tests in.

...read more.

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