Resistance of a Wire

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  1. Planning

  1. The Problem

The experiment is about finding how the resistance of a piece of wire changes as you increase its length in 15 cm amounts each time.

In this piece of coursework, I have been asked to investigate the factors that affect the resistance of a nichrome wire. There are many things that affect the resistance of a nichrome wire but I am investigating how the length of the wire will affect its resistance.

  1. Outline

Firstly I will explain what resistance is and how it works. Resistance is when electrons travelling in a material collide with the atoms of the material. The collisions between the electrons and the nuclei cause the electrons to move slower, this is called resistance. So, resistance is how hard it is for the electrons move through a wire material.

The uncontrolled factors that will affect the resistance of the wire are:

  • Firstly, temperature is a factor. If the wire is heated, the atoms will move around more because there will be an increase in energy. This would cause more collisions between the nuclei and the electrons. The increase in collisions would cause the resistance to rise.

    The temperature factor would be very hard to control, because the equipment needed to keep a constant temperature has not been given to us. So we will attempt to do this by being as quick as possible when taking the readings so as to have the same temperature throughout the experiment.

  • Secondly, the thickness of the wire is a factor. The thickness of the wire will cause resistance to decrease because of the increase in space in the wire. The increase in space means that there is more space for the electrons to flow freely because there would be fewer collisions with atoms.

  • Thirdly, the material used would be a factor. If the material being used contains atoms with a large numbers of free electrons on the outer shells, then this means there are more electrons available. So, in theory, if the material is dense the number of atoms is high so the number of free electrons is also high. However if the atoms in the wire are dense with little free electrons, then this will cause an increase in resistance, due to frequent collisions with the nuclei.

  • Finally, the length of the wire is a factor. The longer the wire, the longer it will take electrons to get to the end of the wire. This is because there will be more collisions between electrons and nuclei. So, in theory, the length of the wire should be directly proportional to the resistance. This is because electrical resistance may be thought of as an interference with the free flow of electrons. If the wire were a superconductor, there would be no obstacles to this flow and resistance would be zero, regardless of the length. But there are impediments and the longer the wire; the more of these are encountered.
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One obstacle to the free flow of electrons is the lattice of the atomic nuclei that make up the metal. Another factor is impurities in the metal, which have a higher resistance than the pure metal. If you double the length of the wire you have twice as many of these obstacles to overcome.

  1. Steps to Ensure Accuracy

Things we can use to ensure the accuracy of the results of the experiment are:

  • Accurate multi-meters so that you get accurate results and not too many anomalies
  • Accurate metre rule so that you get ...

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