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Science Investigation Into What Affects The Resistance Of A Wire

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Introduction

Science Investigation Into What Affects The Resistance Of A Wire By Owain Bristow 10E3 I am investigating what factors will affect how much resistance a wire will give to a current of electricity passed through it. Possible factors I could investigate are: * Length of the wire. * Cross sectional area of the wire. * Material the wire is constructed from. * Tension of wire. * Temperature of the wire. * Amount of current passed through wire/ amount of voltage. * Light shining on wire. I have chosen to investigate the length of the wire used in my experiments, because it is one of the easier ones to do with the equipment available to me and will produce a line graph. Doing a material investigation would yield a bar chart so would not give a complete explanation, it would be quite hard to alter the wire's temperature or try and investigate the effect of light. Changing a wire's tension would also make it thinner and so alter its surface area. I already know by Ohm's Law that in a fixed length and thickness of metal with a constant temperature the current is directly proportional to the potential difference so the resistance is always the same, with it equalling V/I. ...read more.

Middle

All my measurements will be given correct to two significant figures. Safety To be safe I will use a low voltage during my experiments so that the wire is not burnt (and neither am I) and no equipment is damaged. I will not to electrocute myself, turning the power on after I have let go of the wire. I will make sure I do not short circuit anything. Between experiments I will keep the power pack switched off. Results Length Of Wire Investigation Length of wire (cm) Current1 (A) Current 2 (A) Current 3 (A) Average Current (A) 1/current (A-�) Resistance-2/I (?) 5 2.80 2.60 2.47 2.62 0.382 0.763 10 2.00 2.00 1.85 1.95 0.513 1.03 15 1.45 1.60 1.60 1.55 0.645 1.29 20 1.20 1.40 1.35 1.32 0.758 1.52 25 1.10 1.15 1.10 1.12 0.893 1.79 30 1.00 1.00 0.90 0.967 1.03 2.07 35 0.850 0.850 0.850 0.850 1.18 2.35 40 0.750 0.800 0.700 0.750 1.33 2.67 45 0.700 0.700 0.650 0.683 1.46 2.93 50 0.600 0.600 0.600 0.600 1.67 3.33 Conclusions My graph of 1/current against wire length shows that the relationship between the amount of current and the length of wire is inversely proportional, as the wire gets longer less current is able to flow through it. ...read more.

Conclusion

To get more evidence to support my conclusion I could try the experiment at a different voltage, or keep the current constant or use a different material wire, to see if the results are similar to my present results. To extend this investigation further I could also investigate the cross sectional the wire and how this would affect its resistance. I could then with the results of both investigations find out whether there is a connection between the length of the wire, its cross sectional surface area and its resistance. I could also investigate the other possible factors such as temperature of wire and materials, with different numbers of free electrons, to find how they affect the resistance and if so, do the results obtained show similar patterns to the length investigation. According to Physics by Robert Hutchings and other A-Level textbooks the length L, cross sectional surface area A and resistance R of a wire are linked by the formula: ?=RA L Where ? is the resistivity constant of the material in Ohm metres, R is in Ohms, A is in square metres and L is in metres. Therefore I can check the accuracy of my results by substituting the values I obtained into the formula to see if the answer matches the actual resistivity of the metal constantan quoted in the book to be 49 x 10 ...read more.

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