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Resistance of a wire.

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Introduction

Resistance of a wire Saira_uk01@yahoo.com The problem Our aim is to find out how the electrical resistance of a wire changes in relationship to its length. For this experiment there are four different variables: length, diameter, material and temperature. In this experiment we will change only one variable, the length of the wire. The diameter of the wire is kept constant throughout the experiment so that it is clear from the formula if the resistance is directly proportional to the length. The material of the wire must also be kept the same as different materials have different conductivity. We must keep the surrounding room temperature the same because if the temperature is increased the particles in the wire will move faster and this will therefore have an effect on the resistance. Prediction I predict that as the length of the wire increases so will the resistance of the wire. So the longer the wire the longer distance the electrons will have to travel and so more collisions will occur, so there is more resistance and if you doubled the length of wire, you would double the resistance of the wire. ...read more.

Middle

Plan 1) In a circuit connect a power pack, Ammeter and variable resistor in series, and then connect a voltmeter in parallel. 2) Set up a metre ruler again, with the constant wire along it. Connect the ammeter and voltmeter to the wire at each end to read the voltage and current. 3) Start with your first length of wire (10 cm). Then stopping along the wire at each of the lengths. 4) Using the variable resistor, keep the ammeter reading the same each time. In doing this you will keep the current the same. 5) Read off the voltmeter reading. Do this for each length five times so an average can be taken. 6) Once the recording of results has been done, you can now use these results to work out the resistance of the wire. Fair test: In this experiment we are only changing one factor, all the rest will have to be kept constant through out the whole experiment. Accuracy: To keep this experiment as accurate as possible we need to make sure, firstly, that the length of the wire is measured precisely from the inside edge of the crocodile clips, making sure that the wire is straight when we do this. ...read more.

Conclusion

1 0.17 0.36 2.12 2 0.20 0.43 2.15 3 0.28 0.60 2.14 4 0.38 0.79 2.08 5 0.73 1.53 2.10 Conclusion From the above results I can see that as the length of the wire has increased so has the resistance, as is stated in my prediction. The resistance increases with the length because when there is a longer wire more metal atoms come in the way of the electrons. My results prove that as the length increase so does the resistance. If the voltage is doubled so does the current. This shows that Ohms law is correct. My graph illustrate... Evaluation I think that overall my experiment went well and produced accurate results. The graph doesn't illustrate Ohms law accurately as, Ohms law can only be accurately proved providing the temperature is constant at all times. We cannot be sure that the temperature remained the same during the experiment. I don't think there were any outstanding anomalies, although the experiment could have been more accurate. Criticizing my experiment one improvement I could have done is I could have made sure that the temperature is constant, by keeping the length of wire in a water bath at a constant temperature. Overall the experiment went well and I think there was enough evidence to support my results. ...read more.

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