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# What affects the resistance of a wire?

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Introduction

Hannah Sawyer 11B6 Physics investigation - What affects the resistance of a wire? This investigation is going to show how the resistance of a wire changes with its length. Plan - During any physical process there is usually some kind of friction, in a wire that is carrying electricity (free electrons, which are electrons that are on the outer shell of an atom and can therefore move) there is also friction but it is called resistance (opposes the current). There are four main factors that affect resistance in a wire (affect the movement of the free electrons) these are temperature, composition, cross sectional area and length. Conduction is the opposite of resistance which means as one increases the other decreases and the other way around. Composition - The movement of the electrons in the wire (electricity) is affected by composition because if there were more free electrons then the wire would conduct better and therefore the resistance would be lower. This is because if the distance between the metal atoms is larger it is more difficult for the electrons to move from one atom to another meaning that it can't conduct as well and the greater the resistance. Temperature - To transfer the energy from atom to atom the electrons move from atom to atom. ...read more.

Middle

V (V) I (A) R (?) 1000 1.2 0.10 12 900 1.1 0.10 11 800 1.0 0.10 10 700 0.8 0.10 8.0 600 0.6 0.10 6.0 500 0.5 0.10 5.0 400 0.4 0.10 4.0 300 0.3 0.10 3.0 200 0.2 0.10 2.0 100 0.1 0.10 1.0 (See next page for preliminary tests graphs) I found that the wire that gave me the best results, where there was little scatter from the line of best fit, was the 0.24mm wire. Results - Using a 0.24mm wire with an input of 0.1A - l (mm) V (V) I (A) R (?) Average R 1000 1.2 1.2 0.10 12.0 12.0 12.0 900 1 1.1 0.10 10.0 11.0 10.5 800 0.8 0.9 0.10 8.0 9.0 8.5 700 0.7 0.8 0.10 7.0 8.0 7.5 600 0.6 0.7 0.10 6.0 7.0 6.5 500 0.5 0.6 0.10 5.0 6.0 5.5 400 0.4 0.4 0.10 4.0 4.0 4.0 300 0.3 0.4 0.10 3.0 4.0 3.5 200 0.2 0.2 0.10 2.0 2.0 2.0 100 0.1 0.1 0.10 1.0 1.0 1.0 Using a 0.24 wire with an input of 0.2A - l (mm) V (V) I (A) R (?) Average R 1000 2.3 2.2 0.20 11.5 11 11.25 900 2.0 2.0 0.20 10.0 10 10 800 1.8 1.7 0.20 9.0 8.5 8.75 700 1.6 1.5 0.20 8.0 7.5 7.75 600 1.5 1.3 0.20 7.5 6.5 7.0 ...read more.

Conclusion

The metal that the wire would be made from would need to be considered if accurate readings were required. The metal we used was an alloy called constantan, so a metal with similar properties would need to be used. Copper could not be used because it conducts very well and the resistance would be so low it would be very difficult to read off accurate readings from the voltmeter. Copper is also not a very hard metal and it stretches easily and without knowing it the wire could become longer and thinner than it started off to be and this would produce inaccurate results as you would be changing more than one variable. Nichrome, an alloy of Nickel and Chromium would be a good metal wire to use, as it doesn't conduct very well meaning that the resistance is high, this would mean that the volt readings could be recorded accurately and therefore this would give accurate results. By using this different metal but with the same equipment and variable and then comparing the lines of best fit on the graphs with the ones that were produced from using constantan then we can tell whether or not the increase of resistance was because of the length of the wire and these results were not just correct for one type of wire. ...read more.

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