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what affects the resistance of a wire

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What Affects the Resistance of a Wire?

Before experiment


In this experiment I am going to find out the resistance of a wire at different lengths. I am going to measure the resistance and change in the wire.

We have chosen to do this experiment because I know that the resistance will change if you change the length.


My prediction of the experiment is that the longer the wire the more resistance and so then shorter the wire the less the resistance.


The reason why I think this because if the wire is longer there is more ions for the free electrons to crashing to causing collisions.

So because of this if takes energy so there is less voltage and much more resistance.

Consequently if you put a charge through a shorter wire there is a lower number of ions that collide into causing the higher Voltage and lower resistance.

Fair Test

As because other things can affect the resistance of a wire we have to make it a fair test so because the temperature can affect the wire resistance we have to keep them the same temperature.

...read more.


  1. The voltage on the power supply should be 2 volts.
  1. The lengths of the wires should be 6,12,18,24,30,36,42,48,54,60 centimetres.
  1. Take the results of voltage and current, then using the Q / I * T (divide voltage against current) you can find the resistance.

Repeat steps 1-4.


From my experiment I have found that the longer the length the higher the resistance (ohms).

As I find in my prediction when ever I added 6 cm of wire to the circuit the ohms increased slightly, the current actually decreased and so the voltage.

So the pattern is ………

As the length increased the current decreased. As the length increased the ohms increased.


I believe the reason for this pattern is that for a short wire the current would be higher as the electrons only have to travel a short distance so they would only collide minimally taking not so much energy

Compared to a longer wire which would have more collisions so the electrons lose more energy.  


To evaluate this experiment we must look at the problems that have occurred.

Firstly I look at the anomalies.

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If I were to conduct another experiment I would change the type of wire because this will help me find out if my results comply with other materials.

  • So first I would set up my experiment like my circuit diagram but with different wires.
  • Then I would test wires made of copper ,brass,iron,ect
  • Then I would repeat the test twice again.

Id expect that copper would have little resistance as it has a lot of free electrons so a lot electrons would pass through against not many ions knocking not so much with little resistance while iron has got so many free electrons so the resistance is higher as electrons have to knock into more ions causing higher resistance.

So in which proves my theory that the more ions the higher the resistance but the more free electrons the less resistance.


...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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