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Planning an investigation

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Introduction

Planning an investigation Obtaining Evidence For my investigation I wired several different wire all with different properties and width of wire to collect results for different resistance in wires. The three different types of wire I used were Constantan 28 wire Constantane32 and copper wire 28. Each wire was subjected to 2 volts at various different lengths of the wire. I measured the voltage and amperes every 10-center meter down a meter long length of wire. 28 Constantan wires are o.40mm in diameter and Constantan 32 was 0.28mm in diameter, which is 1/4 smaller then 28 I got this information from a secondary source Philip Harris Catalog. I turn I wired up each wire as 100cm subjected it to two volts then measured the amperes and voltage. The results I've obtained show slight internal resistance as the current increases but this difference we assume is negligible we can safely ignore this factor. ...read more.

Middle

0.17 1.00 0.17 80.00 0.21 1.50 0.14 80.00 0.16 1.10 0.15 70.00 0.20 1.60 0.13 70.00 0.15 1.10 0.14 60.00 0.19 1.70 0.11 60.00 0.14 1.20 0.12 50.00 0.19 1.70 0.11 50.00 0.13 1.20 0.11 40.00 0.14 1.80 0.08 40.00 0.11 1.30 0.08 30.00 0.11 1.90 0.06 30.00 0.09 1.30 0.07 20.00 0.10 2.00 0.05 20.00 0.07 1.30 0.05 10.00 0.06 2.10 0.03 10.00 0.03 1.40 0.02 Constantan 32 1 Constantan 32 2 Length of wire (cm) V in volts I in amps R is ohms Length of wire (cm) V in volts I in amps R is ohms 100.00 0.69 0.06 11.50 100.00 0.72 0.04 18.00 90.00 0.68 0.06 11.33 90.00 0.69 0.04 17.25 80.00 0.67 0.06 11.17 80.00 0.68 0.05 13.60 70.00 0.66 0.08 8.25 70.00 0.67 0.07 9.57 60.00 0.65 0.08 8.13 60.00 0.66 0.09 7.33 50.00 0.63 0.10 6.30 50.00 0.65 0.10 6.50 40.00 0.60 0.12 5.00 40.00 0.62 0.12 5.17 30.00 0.58 0.16 3.63 30.00 0.61 0.18 3.39 20.00 0.58 0.20 2.90 20.00 0.50 0.21 2.38 10.00 0.43 0.32 1.34 10.00 0.47 0.41 1.15 Constantan 28 1 Constantan 28 2 Length of wire (cm) ...read more.

Conclusion

We can prove that Ohms law works by looking at Constantan wire. 50cm = 6.30 ohms 100cm = 11.50 ohms This shows that Constantan wire when doubled in length will double in resistance. Evaluation My prediction that when doubling the length of the wire the resistance would double also was in the Constantan wire true, therefore we can assume it follows ohms law. The copper wire seamed to follow ohms law until we got to the shorter lengths of wire were the length of wire was sufficient to heat up and disorientate the graph, Thus from this we can see that copper doesn't obey Ohms law. The double the length the double resistant could be interpreted into the more wire mass the current flows in the more resistance, If this is so if you doubled the diameter you should double the resistance as well. I'm undecided whether my results would be different for the Constantan wire if we used a longer wire strip and a increased voltage we may have had a different story. ...read more.

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