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# to see how the resistance of a wire changes when you change the length.

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Introduction

Emma Crane 10.NJ Physics Coursework PLAN Aim My aim is to see how the resistance of a wire changes when you change the length. Method Diagram of set-up: Apparatus needed: Power Pack, Voltmeter, Ammeter, Leads, Constantan Wire, 2 Crocodile Clips, A metre ruler, Sellotape. Set-up a circuit as in the diagram above. Sellotape the wire to the metre ruler. Set the Power Pack on to 2V. Change the length of the constantan wire each time and record the ammeter and voltmeter readings. I will then calculate the resistance by dividing the voltage by the current. Fair Test I will not keep the power pack on for too long at one time because the wire will get hot and the particles may start to move around. I will keep the power pack at the same voltage all the time. I will use the same ammeter and voltmeter for the experiment and any repeats. Range To collect my results I have decided to take an ammeter and voltage reading. ...read more.

Middle

So to my results tables I have added the column length divided by area which is the other part that I need to work this out as well as the resistance. RESULTS Ist time Length of Wire (cm) Voltage (volts) Current (Amps) Resistance (ohms) 10 0.8 2.0 0.4 20 1.0 1.5 0.7 30 1.2 1.2 1.0 40 1.3 1.0 1.3 50 1.4 0.8 1.8 60 1.4 0.8 1.8 70 1.5 0.7 2.1 80 1.5 0.6 2.5 90 1.5 0.5 3.0 100 1.6 0.4 4.0 Ist Repeats Length of Wire (cm) Voltage (volts) Current (Amps) Resistance (ohms) 10 0.8 2.0 0.4 20 1.0 1.4 0.7 30 1.2 1.1 1.1 40 1.3 1.0 1.3 50 1.3 0.8 1.6 60 1.4 0.7 2.0 70 1.5 0.6 2.5 80 1.5 0.6 2.5 90 1.6 0.5 3.2 100 1.6 0.5 3.2 Comparing my two lots of results I still think that there are some which don't quite look right so I have decided to do one more set of repeats. 2nd Repeats Length of Wire (cm) Voltage (volts) Current (Amps) Resistance (ohms) ...read more.

Conclusion

Comparing these figures I would say that my results were quite accurate as the difference is 0.0000003m. EVALUATION From my method I was able to easily achieve a set of results. I think that the method I chose to use was quite reliable. If I were to do this investigation again I would come up with a better way of doing it though to get more accurate results because the wire kept bending so I am not sure that the distances we measured at were very precise. As I mentioned before I think that I only had one anomaly and did not use this in working out my averages. I think we got this anomaly because near to the end of the investigation we started to rush becoming a bit more careless, maybe living the power pack on which would of increased the resistance because the wire would have been hotter. Firm conclusions that I can make are: * The longer the wire the more resistance there will be. * Resistance and Length are proportional. * Resistivity of a constantan wire is about 4.9 X 10 metres. ...read more.

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