Resistance of Nichrome Wire

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Resistance of Nichrome Wire

Physics Coursework

Aim: To investigate how changing one or more variables about Nichrome wire, affects its resistance in a series circuit.

Variables:

        To be able to get results on resistance of a piece of Nichrome wire I will need to change at least one variable so that the results of resistance change and I can record/see patterns of change. There are several variables which can be changed during this experiment. These are:

  • Length of Wire
  • Thickness of Wire
  • Density of Wire
  • Fraction Composition of the wire (percentage of elements and compounds within the wire)
  • Using different currents

After consideration I have decided to change 2 variables. These will be

  • Length of Wire
  • Thickness of Wire

I have decided to change these two variables so that I am able to see how the thickness of the wire when used in different lengths will affect resistance. I aim for all the wires to be range from 5cm (0.05m) to 100cms (1m) in intervals of a certain size which will be found out later on in the investigation. With all the lengths like that, when I change the thickness of wire I should be able to see clear differences in how thickness effects resistance, while in the same results being able to see how length also effects resistance. The different thicknesses of wire are 0.26mm and 0.32mm. The resistance will be measured in ohms.  

I have decided to keep the other variables the same as by changing too many will lead to inaccuracy within the results, and there will also be a lot of data which will need to be collect. Some of the variables I listed would be very hard to follow though as:

  • Fractional Composition: to change the percentage of each compound/element in the wirer would be difficult as it would take specialised company to produce this wire for us.
  • Density of Wire: To be able to find the different densities of the wire would be very complicated and take a lot of valuable time.

The easiest variable to change within the whole list would have been the current running though the circuit. As different amount of power flowed though the wire it would produce different amounts of heat energy which would make varied results as the vibrations of the metal atoms might affect the flow of electrons.

Movement of Electrons in a piece of Wire:

Plan: 

        To get my results I will use a Voltmeter and an Ammeter, and then record them in a table before using the formula to work out the resistance (formula shown below)

         As I am changing to variables the accuracy of my results is very important. To ensure the test is fair I will:

  • Make sure that the current in the circuit is always the same: To make sure the current is the same I will chose a certain current in which I will use in all circuits. As I may take for than one lesson to do the practical, I will use a variable resistor to change the current to the one of the pervious lessons. Also the current affects the amount of heat produced. (Higher current means higher temperature). This affects and changes a variable which could affect the results.
  • Make sure the circuit is setup in the same way: Once I have drawn a plan of the circuit I will use, I will not change it or add extra pieces of equipment: I.E. wires, motors, bulbs.
  • Make sure when cutting the lengths that they are accurate: Before cutting the wire shorter I will mark out the intervals, and then check this with my working partner, then cut it.
  • Treat the different results for the widths as a different experiment: I will do this by completing all the lengths for one width first and then a 2nd set of results to check the accuracy, before moving onto the next width.
  • Find the average of the two results to plot in the graph: As I will be doing the tests twice, I will work out the averages of the two results by adding them together and dividing by two. An average will increase the results level of accuracy.
  • Make sure when measuring the lengths 1cm is added to the total length: As the crocodile clips take up space on the wire, to make sure the distance between the clips is exactly the same as what is required.
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The Apparatus I will use are 

  • Wires
  • Crocodile Clips
  • Nichrome wire (max length of 100cm (1m))
  • Voltmeter
  • Ammeter
  • Variable resistor
  • Cell (battery)
  • Ruler
  • Wire Cutters

The circuit will be set up like this:

These are the results from using a computer simulated program. Unfortunately the current varied on this program. This is where these results will differ from mine as our currents will all ways be the same.  From these results I am see that by choosing an interval size of 10cm is good, as there is a good difference between results, ...

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