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Investigation of factors that affect resistance of a wire

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Introduction

Investigation of factors that affect resistance of a wire This coursework is an investigation of factors that affect the resistance of a wire. Electricity is conducted through a conductor, in this case wire, by means of free electrons. The number of free electrons depends on the material and more free electrons means a better conductor as it has less resistance. The free electrons are given energy and, as a result, move and collide with neighbouring free electrons. This happens along the length of the wire and therefore electricity is conducted. Resistance occurs when the electrons travelling along the wire collide with the fixed particles of the wire. These collisions slow down the flow of electrons causing resistance as they convert some of the energy the free electrons are carrying into heat. Resistance is a measure of how hard it is for the electrons to move through the wire. Resistance is worked out using the equation below. R = V/I Where V = voltage and I = current and R = resistance. Ohms Law states that the current in a metal conductor, when kept at the same temperature, is proportional to the voltage (potential difference.) This means that the resistance of a metal conductor will remain constant as long as the temperature also remains constant. This also means that the resistance of a metal will rise as the temperature rises as at higher temperatures the particles in the metal move around more quickly, increasing the chance of collision with free electrons. ...read more.

Middle

Hopefully the graph I draw afterwards will show that the length of a wire is proportional to the resistance. If the resistance increases then the current (in amps) should decrease as I increase the length of the wire. Method Apparatus: Power Supply Ammeter Voltmeter Wire Ruler Crocodile Clips Connecting Wires I will set the above apparatus up as shown in the diagram below. The ammeter and voltmeter I use will both be digital. I have decided to use digital ones because this means the results I collect will be more accurate. If I was to use either an analogue voltmeter or ammeter then my results would not be so accurate as it would depend upon my ability to read off correct results. Safety As with all experiments performed, there are a number of safety risks involved. In order to be as safe as possible I will make sure that my experiment is set up correctly and I will be careful when handling my power supply. Although there is no need for safety goggles in this particular experiment, as I will not be using any chemicals or naked flames, I will take the usual precautions regarding my uniform, ie. Tucking my tie in, just to minimise chance of any accidents happening. I will also, obviously, be careful that I do not conduct my experiment anywhere near water as water is a good conductor of electricity. Fair Test I will make sure that my test is fair by using the same apparatus each time, by repeating the ...read more.

Conclusion

Evaluation From my results table and graph I can see that the results I collected are quite reliable. The line of best fit I have drawn goes through four of my six points. The other two points are also quite close. From looking at the results on my table for these two particular points, I can see that the results for the voltages on them vary by quite a lot, compared to my other results. This could be why they are anomalous. Another possible reason for these anomalistic results is the equipment I used. Although I used a digital ammeter and voltmeter and was careful to use the same apparatus each time, I don't think that the ruler, wire and crocodile clips was a very accurate way of changing the wire length. If I was to repeat this experiment I think I could improve it in several ways. I would try and find a more accurate way of changing the wire length and I would use different, more varied lengths. As we only had the equipment for a maximum wire length of 30cm I felt our experiments were somewhat lacking in variation. If we had a meter ruler and could have tested 15 cm between each reading as a pose to 5 I feel our results may have been somewhat more valid. I would also repeat the experiment again with another variable, such as the temperature or width of the wire and then compare the two results or with more than one metal so I could compare the resistance of both. ...read more.

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