Electrical Conductivity in Metals Experiment by hcj

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									Electrical Conductivity in Metals Experiment Abstract: The purpose of this experiment was to familiarize the students with dependence of the electrical conductivity of metals on temperature. The electrical conductivity of Copper as a function of temperature was determined and the results were compared with those in reference books. In the end of the experiment, it was found that our test results came very close to the theoretical values for copper conductivity. The possible discrepancy could result from the fact that sometimes we could not cool or heat the specimen to the desired temperature. Also we could take the resistance measurements too early, which could also result it a little error. Introduction: In order to minimize power loss due to the internal resistance of the power lines, (P=VI, V2 2 P=R I , P  ) the behavior of numerous conducting materials is studied to find the R best and the cheapest one, so it would have the lowest resistance possible at the lowest cost. Copper was found to be the second best after silver, and followed by gold, both of which are precious materials, which makes copper the cheapest alternative to making wires. We studied the dependence of resistance of copper on temperature. Due to nature of metallic bonds, metals are best conductors at extremely low temperatures. The increase in temperature causes the increase in vibrations of the crystal structure atoms, which interferes with the electron motion. Therefore, the best conductivity of metals is observed in a pure, not cold worked (crystal structure not damaged), and at very low temperatures. In our experiment the four groups used four isolated copper wire spools approximately 87.2 meters in length to determine the dependence of resistance on temperature. Conclusion: Our experimental values proved the theory to be correct, with the internal resistance of the copper wire dropping from 101 Ohm at 102*C in boiling water to only 6 Ohms in liquid nitrogen (-196*C). The resistance was tested at five different temperatures: -196*C in liquid nitrogen, -78*C in dry ice, 0*C in ice water, +21*C at room temperature, and finally, 100*C in boiling water. The experimental data proved the theory to be correct.

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