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This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.
that is drawn from the cell and pass through this part of wire. 3. I placed the iron slice on the wire so as to make sure that there is current flow in the circuit. 4. The iron slice was placed on the wire 5cm away from the end which nipped by the clip.
If the wire obeys Ohm's Law, no matter the voltage and current, the value obtained for resistance from the formula R=V/I, should be the same, meaning three values for one resistance can be obtained, which, if they show to be equal to within experimental error, improves the reliability of the value of R obtained.
If I work out the resistivity based on this result only, I get a value of 1.59x10-6 ?m, which gives the spread of my results to be just 4.70x10-7 ?m, which I believe is very accurate. There was very little discrepancy in my data.
At high temperatures, the resistance of a metal increases proportionately with temperature. This can be shown in this diagram As the temperature of a metal is reduced, the temperature dependence of resistivity follows a complex temperature rule. Mathematically the temperature dependence of the resistivity '?'
If the resistance did fluctuate I would need to change the current, as the rise in temperature of the pencil would affect resistance and thus my results. My results from these settings are as follows : Pencil Length Voltage Current Resistance 171mm 1.03V 0.1A 7.923?
/ m Current(I) / A Current rounded to 3 d.p./A 0.02 0.24 0.240 0.04 0.12 0.120 0.06 0.08 0.080 0.08 0.06 0.060 0.1 0.048 0.048 0.12 0.04 0.040 0.14 0.034285714 0.034 0.16 0.03 0.030 0.18 0.026666667 0.027 0.2 0.024 0.024 0.22 0.021818182 0.022 0.24 0.02 0.020 0.26 0.018461538 0.018 0.28
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