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An experiment to find out how length affects the resistance of a wire.

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An experiment to find out how length affects the resistance of a wire


       My aim is to find out how length affects the resistance of a wire.

This is like a hose-pipe. If you increase the length of a hose-pipe but keep the same width less water will come be let through. The longer the hose-pipe the more resistance it has. . Electricity is conducted through a conductor, in this case wire, by means of free electrons. The number of free electrons depends on the material and more free electrons means a better conductor, i.e. it has less resistance. The free electrons are given energy and as a result move and collide with neighbouring free electrons. This happens across the length of the wire and thus electricity is conducted. Resistance is the result of energy loss as heat. It involves collisions between the free electrons and the fixed particles of the metal, other free electrons and impurities. These collisions convert some of the energy that the free electrons are carrying into heat.

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  • Set up apparatus as in diagram.
  • Also make sure that on the dial the voltmeter is set to 20V, that on the dial the ammeter is set to 20A and that the connections are right.
  • Set the ammeter to show 0.2 on the display by moving the dial on the power pack, this will stay the same throughout the experiments.
  • Make sure to switch on the power pack at the mains after wiring up.
  • Move the crocodile clip along the wire going up in 10’s, the range is 0-100cm.
  • Read the amount of volts measured off the voltmeter at each of these intervals.
  • Record all results.
  • Once all results have been collected work out the resistance, which is volts/amps.
  • Then repeat the experiment for reliability.
  • Work out an average resistance of the 2 sets of results.
  • Draw a graph of the average results.
  • I didn’t have any unreliable results but if any results were taken that seemed wrong compared to the others, that length should be repeated as well to check its reliability.
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It also shows as in my prediction that if I doubled the length that the resistance would also double.


I found the procedure that I used easy to do and it went very well. It also produced the results that I expected. My results were very accurate. Which is shown in the graph, as they are all in a straight line with no anomalous results.

I feel that the experiment was suitable and a good experiment to do. I got out of the experiment what I had expected to.

I think that the only way that I could improve my results are either by doing more experiments for increased reliability, by repeating the experiment with a different wire to confirm my results or by doing a new experiment, by changing thickness and then seeing what the differences there were between the two experiments.

While doing the experiment I knew that the wire would heat up and so it would not be a fair test, so I turned off the power supply between readings so that the test was fair.

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