Physics GCSE Coursework:Factors affecting the resistance of a wire

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Physics GCSE Coursework:

Factors affecting the resistance of a wire

Ali Hlaiyil

 

Introduction:

Before starting my coursework I have decided to choose 2 factors that will affect the resistance of a wire.  I will 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 only pick 2 factors to investigate.

 

Resistance occurs when the electrons traveling along the wire collide with the atoms of the material of the wire. These collisions slow down the flow of electrons causing resistance. Resistance is a measure of how hard it is to move the electrons through the wire.

 

These are some of the factors that affect the resistance of a wire:
- 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 frequent collisions between the electrons and the atoms as the atoms move into the path of the electrons. This increase in collisions means that there will be an increase in resistance.

- Material: The type of material will affect the amount of free electrons that 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, 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 a 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.
- 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.
- Wire width: If the wire’s 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 chose 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 the easiest and best one to record, getting the most accurate results.
To measure the wire width I would use different widths of the same length and same material of wire. To record the difference in widths I would use the same voltage and measure the resistance for each thickness. It would be easy to obtain these results so this would be my first test.
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 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 as the second factor.

 

Background Knowledge/Research:

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.

Resistance is caused when these electrons flowing towards the positive terminal have to 'jump' atoms. So if we double the length of a wire, the number of atoms in the wire doubles, so the number of jumps double, so twice the amount of energy is required;

“There are twice as many jumps if the wire is twice as long”.

The thinner the wire is, there are less channels of electrons in the wire for current to flow, so the energy is not spread out as much, so the resistance will be higher; We see that if the area of the wire doubles, so does the number of possible routes for the current to flow down, therefore the energy is twice as spread out, so resistance might halve. Therefore,

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Resistance= 1/Area.

This can be explained using the formula

R = V/I

Where there is 2 x the current, and the voltage is the same, R will halve. I did some research and it says 'that doubling the area will therefore halve the resistance' - in other words the resistance of a wire is inversely proportional to its area.

As the electrons in an electric current move around a circuit, they bump into the atoms in the wires through which they pass. Atoms of different elements obstruct the electrons by different amounts. For example, electrons ...

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