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Coursework – The resistance of wire

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Introduction

Coursework - The resistance of wire The resistance of a wire depends on certain factors these are: * Temperature * Length * Voltage * Thickness * Material Equipment: * Different lengths of copper wire * Power pack at 12 volts * Crocodile clips * Connecting wires * Volt meter * Amp meter * Heat proof mat * Ruler Intro: Resistance is a force, which opposes the flow of an electric current around a circuit so that energy is required to push the charged particles around the circuit. The circuit itself can resist the flow of particles if the wires are either very thin or very long. E.g. The filament across an electric light bulb. Method: First we connected the power pack to a socket and turned set the current. We connected up the amp and voltmeter to a circuit placing the wire in the middle over a heatproof mat. We measured the resistance of the wire by reading the voltage 3 times for each length of wire and using it to find the average. ...read more.

Middle

This is a graph of my predicted results it shows that the length is proportional to the resistance. Results: Length of wire Volts Amps (current) Average Resistance ( ) 10cm 0.23 0.51 0.22 0.5 / 0.32 0.64 20cm 0.40 0.69 0.45 0.5 / 0.57 1.14 30cm 1.25 1.02 0.64 0.5 / 1.10 2.2 40cm 0.85 1.73 0.88 0.5 / 1.15 2.3 50cm 1.08 1.84 1.08 0.5 / 1.33 2.66 60cm 1.32 2.60 1.29 0.5 / 1.73 3.46 70cm 1.52 2.68 1.53 0.5 / 1.91 3.82 80cm 1.68 2.76 1.56 0.5 / 2 4 90cm 1.70 3.76 1.90 0.5 / 2.46 4.92 1m 2.14 4.07 2.14 0.5 / 2.69 5.38 Graph on separate sheet The graph is a straight line through the origin, which means the resistance is directly proportional to the length. This means that if the length is 40cm, and resistance is 2. Then if length is doubled to 80cm, resistance also doubles to 4. My results are not perfect but show this quite accurately. This is because of the scientific idea, stated in the planning that if you double length, you double the number of ions in it, so doubling the number of electron jumps, which causes resistance. ...read more.

Conclusion

The ammeters and voltmeters could have been damaged and reading falsely on both the meters used. I would use a digital voltmeter instead of an analogue meter. I would do this because a digital voltmeter is a lot more accurate than an analogue because if the needle in the analogue voltmeter is bent then the readings given off will be false whereas a digital voltmeter does not rely on a needle or any other manual movements. The wire might not be completely straight, it may be of different thickness throughout the length. These would have contributed as well to an error. These results would be difficult to improve on as they are reasonably accurate, and there were no anomalous results. But if I were to do this experiment again, I would use newer, more accurate ammeters and voltmeters, a more accurate method of measurement, and take a much wider range of readings, and more readings so that a more accurate average can be taken. I would also investigate other factors, such as temperature, voltage and current, and see how these effect the resistance. I would also do the experiments under different conditions such as temperature and pressure to see if it makes any difference to resistance. Naomi Ringer 11EW Resistance of wire coursework. ...read more.

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