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To investigate the factors affecting the resistance of a piece of wire.

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Natasha Brilliant

Investigation into the Factor(s) that Affect the Resistance of a Piece of Wire

The purpose of this investigation is to investigate the factors affecting the resistance of a piece of wire.  In order to investigate these factors I will need to carry out a series of experiments.  I will also need to research some background information using secondary sources.  I will then need to consider the equipment that I will use and the number of readings I will take for each experiment.  I will need to finally try to ensure that my results are as reliable and precise as possible while considering the safety aspect of my experiments.

Electrical resistance is a quantity which measures the amount of opposition a circuit or individual component provides to the electric current (charges) trying to flow.  The amount of resistance in an electrical circuit determines the amount of current flowing for any given voltage applied to the circuit.

The unit of resistance is the ohm, discovered by the German physicist, Georg Ohm.  One ohm is the amount of resistance that limits the current to one ampere when one volt is applied to it.

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Some wires have more useful properties than others do.  An example of this is constantan wire which is an alloy of copper and nickel and whose resistance is unaffected by temperature.  image00.png


  1. Temperature

Temperature will affect resistance I think (except in the case of the constantan wire – see ‘Type of Wire’ above) because as the wire heats up, the electrons will gain kinetic energy and start to vibrate.  This will make it harder for them to ‘travel’ along the wire making the resistance higher.  During my experiments I may find that I have to pause so that they wire can cool down so that it doesn’t affect the resistance too much.       image03.pngimage02.png

For my investigation, I am going to investigate two of the above factors thoroughly so that I may come to a conclusion about what affects the resistance of a piece of wire.  I have chosen to investigate the length of the wire and the cross sectional area of the wire.

In my investigation, I am going to use two different methods to investigate each factor.  In order to investigate

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Current =   Voltage  _        or        I = V

                                    Resistance                      R

 Rearranged it gives us:

                        Resistance = Voltage        or        R = V

                                         Current                        I

Preliminary Experiments

Before I conduct my experiments, I needed to do some preliminary work to determine which wires I am going to use.  I had six options to choose from:

Constantan or Nichrome wire in the any of the following thickness:

   0.28 mm or

    0.40 mm or

0.56 mm

I did a similar experiment for length as detailed above for all six wires but I only took five readings (at every 10 cm) because I do not need such detailed results.  I did not repeat the experiment.  I then chose the thickness that offers the biggest range of readings, as it will be clearer to analyse my results if they are not too similar.  Overleaf are my results.

The graph clearly shows that the Nichrome wire with a 0.28mm cross sectional area has the biggest range (2.3 Ω to 9.9 Ω giving a range of 7.6 Ω).  I will therefore use this wire in my length experiments.  However, if time permits, I will test as many of the six wires as possible meaning that I will have more results to compare and analyse.  

...read more.

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