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# How the resistance of a piece of wire changes with length

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Introduction

How the resistance of a piece of wire changes with length Planning Research; - Electricity is the flow of electrons from negative to positive: the opposite direction from which they are measured. - Electricity flows, due to the outer electrons in a metal being loose and hence they can flow. - The free electrons are moving very fast inside the metal (1/1000 of the speed of light) but another electron will be moving in the opposite direction with the same speed. This means that there is no net flow of charge and so no current - When connected to a circuit, the power source creates kinetic energy in the electrons. These accelerate and collide with the metal - Resistance is caused due to the atoms in the metal colliding with the flowing electrons. The metal ions will then gain vibrational energy, which is converted into heat. The electrons lose kinetic energy. - As there is a higher length of wire, so will there be more metal atoms for the flowing electrons to collide with. Hence, as the length of the wire increases, so will the resistance of the wire. - Resistance can be calculated using Resistance (ohms)=Voltage (Volts) Current (Amps) This had led me to make my: Prediction; I predict that as the length of wire increases, so will the resistance of the piece of wire increase. This is because of the increased amount of metal atoms for the electrons to collide with. ...read more.

Middle

1 2 3 4 5 Average Resistance (?) 10 0.41 0.41 0.42 0.4 0.41 0.41 0.953488372 20 0.8 0.8 0.8 0.8 0.8 0.8 1.860465116 30 1.17 1.16 1.16 1.16 1.17 1.16 2.697674419 40 1.53 1.54 1.53 1.52 1.52 1.53 3.558139535 50 1.91 1.92 1.92 1.9 1.91 1.91 4.441860465 60 2.28 2.27 2.28 2.27 2.27 2.27 5.279069767 70 2.65 2.65 2.66 2.66 2.65 2.65 6.162790698 80 3 3.05 3.04 3.01 3.03 3.03 7.046511628 90 3.43 3.41 3.42 3.42 3.43 3.42 7.953488372 100 3.8 3.81 3.82 3.8 3.8 3.81 8.860465116 I made sure I did this with precision and skill by ensuring that the loose voltmeter wire was touching at exactly every 10cm. I also waited 3 seconds before each reading, to make sure that the reading was constant. I also made sure that the current reading was EXACTLY accurate, as this could adversely affect the resistance calculations. Analysis This graph shows that as the length increases, so does the resistance. It shows positive correlation. This is because as the length increases, so does the number of metal ions present. This would mean that there are more ions for the electrons to collide with, just as I had stated in my prediction. My results show this very conclusively. It also shows that as current increases, the resistance is unchanged. This can be confirmed by rearranging the formula R= V/I to leave V=IR, meaning that the voltage across the piece of wire is proportional to the resistance, as the current is a constant unless the power input is changed. ...read more.

Conclusion

I think that our results are sufficient to support my conclusion, although I would like to try a few other variables to check how other factors can affect our results. This might give me a better impression of how our experiment was inaccurate. Some of these variables are: - CSA (cross-sectional area) of wire If I were to investigate CSA, I would use 5 different CSAs of wire. I would then decide on a fixed length, and take 5 repeats for each piece of wire. As the wire gets thicker, the resistance would increase, again due to there being more ions for the electrons to collide with - Current If I were to look directly at current, I would use a fixed length, and just change the current entering the piece of wire. I would use 5 different currents, and, again, have 5 repeats. - Type of wire If I investigated the type of wire, I would use wire made out of Constantine, Copper, Nichrome, Aluminium and Manganin. I would then choose a fixed length, and take 5 repeats for each type of wire. The better conductors (Copper, Aluminium) would provide less resistance due to them being better conductors. - Temperature of experiment I would use a fixed piece of wire, and length, and change the temperature, if I were to investigate this. I would use 5 different temperatures, and have 5 repeats. As temperature increases, resistance would increase, due to the metal ions having more energy, and vibrating more, causing more collisions, and hence the electrons would be slowed more. ...read more.

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