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# What affects the resistance of a piece of wire?

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Introduction

What affects the resistance of a piece of wire?

For my investigation I will investigate the resistance of a piece wire, the variables are, the length and with and temperature of the wire and the current. The variables I am going to investigate are the length of the wire and the current that passes trough it. I will do this for five different lengths of wire, 5, 10, 15, 20 and 25cm, and two different currents, 6 and 12v. My prediction is that the longer the length of wire the higher the voltage, as the voltage increases so will the resistance. This happens because as the length of the wire increases the number of positive and negative electrons also increases. I have made this prediction because I looked back similar experiments and the results were the same as I have written in my prediction.

Middle

Crocodile clips

Ammeter

Voltmeter

Ruler

Variable resistor

DC

Method

I will set up the apparatus as shown in the diagram above and measured the length of wire with a ruler and put crocodile clips on it. I will set the power pack to 6v because it is the first experiment. I will add a voltmeter, ammeter and variable resistor it to my circuit were shown on my diagram. I will then switch on the power pack and look the reading of the volt and ammeter. I will take the readings twice to make my results more accurate, and then find the average; I will do this for each length of wire. I will then work out the resistance by using the rule R=V divided by I. I will do this again but this time with the power pack set to12v.

Conclusion

v the voltage on the voltmeter with a 5cm piece of wire read an average of 0.02v and a resistance of 0.02ohms, but with the power pack still on 12v and this time a 25cm piece of wire the voltage on the voltmeter read 0.04v and the resistance 0.035ohms and not 0.02ohms, so this shows the resistance has increased along with the voltage and proved my prediction correct. My results conclude that the increase in voltage across a piece of wire affects the resistance of the wire.

Evaluation

If I were to do this experiment again I would test more lengths of wire, ten rather than five, because this would make my results even more accurate. I think I would also choose to test each wire with tree voltages rather than two, again to make my results more accurate.

Overall I think the experiment was successful and showed what effects the resistance of a piece of wire.

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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