The resistance of a wire.

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Kieren Phillips.                                          

Physics Coursework.

Before starting my coursework I have decided to choose a factor that will affect the resistance of a wire. I shall do this by going through all of the factors that affect the resistance of a wire and how I would measure each factor to find out which would be the most effective and easiest factor to measure. Below is a list of factors and reasons why they affect the resistance of a wire. From this list of factors I will pick one factor to investigate.

Factors
1.
Temperature: If the wire is heated up the atoms in the wire will start to vibrate because of their increase in energy. This causes more collisions between the electrons and the atoms as the atoms are moving into the path of the electrons. This increase in collisions means that there will be an increase in resistance.
2.
Material: The type of material will affect the amount of free electrons, which are able to flow through the wire. The number of electrons depends on the amount of electrons in the outer energy shell of the atoms, so if there are more or larger atoms then there must be more electrons available. If the material has a high number of atoms there will be high number of electrons
causing a lower resistance because of the increase in the number of electrons. Also if the atoms in the material are closely packed then the electrons will have more frequent collisions and the resistance will increase.
3.
Wire length: If the length of the wire is increased then the resistance will also increase as the electrons will have a longer distance to travel and so more collisions will occur. Due to this the length increase should be proportional to the resistance increase.
4.
Wire width: If the wires width is increased the resistance will decrease. This is because of the increase in the space for the electrons to travel through. Due to this increased space between the atoms there should be less collisions.

To choose which factor I am going to investigate I am going to consider how I would measure each factor and which factor would be the best and easiest to record.

To measure the wire width I would use different widths of the same length and same material of wire e.g. thin, medium and thick copper wire with thin and thick adjustable wire. To record the difference in widths I would use the same voltage and measure the resistance for each thickness. Although it would be easy to obtain and record the data the graphs that I would be able to draw up would not be
interesting.
         For the temperature of the wire I would not be able to carry out a fair test because it is extremely difficult to produce and control the range of temperatures needed without the correct equipment.
         If I chose to measure the difference in the resistance in different materials I would chose a number of different materials and using the same voltage I would record the resistance given by each wire of the
same length and width. Although once again it would be simple to record these results the graphs that could be drawn would not show any connection between the material and the resistance because of the limited number of materials I could test with the equipment available.
         The final factor is the length of the wire. To measure and record the findings for this factor would be simple and the results collected could show a connection between the length of the wire and the
resistance given by the wire. This is why I have chosen to investigate this factor.

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Plan.  

        In this investigation my aim is to investigate how the length of a wire affects the current and resistance of a wire.

Scientific Knowledge.

Metals conduct electricity because the atoms in them do not hold on to their electrons very well, and so creating free electrons, carrying a negative charge to jump along the line of atoms in a wire. Depending on the material of the wire the number of atoms it contains will vary. When the electrons of a circuit are travelling along the wire and they collide with the atoms of the wire the flow of ...

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