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Our aim for this investigation is to find out how the electrical resistance of a wire changes in relation to the size of the wire:~

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Introduction

Craig Anderson Investigation of Resistance 19th May 2002 Our aim for this investigation is to find out how the electrical resistance of a wire changes in relation to the size of the wire:~ Theory:~ Electricity is conducted by a conductor; by means of free electrons (Our conductor is the wire). The conductivity of an object depends on the number of free electrons, therefore depending on the material used. For example; Gold has more free electrons then iron does, this tells us that gold is the better conductor. In a circuit, free electrons are given energy and as a result collide with neighbouring free electrons. This occurs throughout the wire, and this is how electricity is conducted. The result of energy lost as heat is called resistance. It involves collisions between the free electrons and the fixed particles of the metal. These collisions convert some of the energy that the free electrons are carrying into heat. We can tell that the better conductor; the lower the resistance, and in order to find the resistance of a wire, we must use Ohm's law:~ The formula we use is Resistance (R) = Volts (V) ...read more.

Middle

I will also be keeping the experiment at room temperature constantly through the investigation; this will make it a fair test. Apparatus:~ Constantan wire Power supply Two crocodile clips Voltmeter Ammeter Safety:~ This experiment is not particularly dangerous, although we are going to avoid using a wire that is less then 0.375 mm in diameter to avoid over-heating. Also handling the equipment with wet hands or near water is to be avoided entirely. Fair test:~ In order to make this a fair test, the lengths of constantan must be exact and should not differ when the experiment is carried out for a second time. Prediction:~ I think that the thicker the wire, the less resistance there will be. This is because there is more space for the atoms to move freely, reducing the number of collisions. Results:~ First attempt: SWG Width of wire Volts Amps Resistance 28 0.375 1.5 0.44 0.66 0.75 1 0.6 0.6 18 1.125 0.6 0.7 0.42 14.5 1.875 0.8 0.45 0.36 13.5 2.25 0.4 0.73 0.292 10.5 3 0.4 0.72 0.288 Second attempt: SWG Width of wire Volts Amps Resistance 28 0.375 1.55 0444 0.6882 0.75 1.2 0.7 0.84 18 1.125 0.65 0.75 0.4875 14.5 1.875 0.5 0.8 0.4 13.5 2.25 0.4 0.73 0.292 10.5 3 0.39 ...read more.

Conclusion

My results fulfilled my aim and complied with the prediction I made and the background theory that I had assembled. The results supported my prediction because the background reasoning I used to produce the prediction specifically explained the behaviour of the flow of electrons which would be affected by resistance. Unfortunately, an inaccurate result occurred during the second attempt, and this can be seen clearly on the graph. This inaccurate result could have been due to faulty equipment, improper use of the equipment, or even that the wrong sized wire was used during the experiment. We assume that the results probably would have been more accurate if further experiments had taken place. This would give a better example of what the results for this experiment should be like. Also a wider range of various sized wires would have given a larger view of how resistance is affected by certain aspects of a wire. All the equipment should have been checked for faults before each experiment to show if they gave the correct readings. These readings should have been viewed by each person participating in the experiment in order to abolish incorrect readings that would obviously lead to inaccurate results. Though the graph and the tables do show a decrease in resistance due to an increase in the wires width, so my experiment was still successful. ...read more.

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