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# Investigation: Which Factors affect the Resistance of a Wire

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Introduction

Investigation: Which Factors affect the Resistance of a Wire Aim As part of my Year 11 coursework I am investigating what factors affect the resistance of a wire. For me to do so there will be a number of factors that I will have to investigate. This will include how length, cross sectional area, material, and temperature affect the resistance of a wire. The three wires that I will be investigating will be Copper, Nichrome and Constantan. It my aim, also, to find out which of these wires conduct electrical current the best and which do not. Secondary/Background Info Resistance involving electricity is a part of an electrical circuit that transforms electrical energy into heat energy in varying electric current. Resistance involves charged particles and fixed particles colliding, this makes up the structure of the conductors. It is often thought as "restricted" in household and electrical appliances such as lamps, heaters, and resistors, but it is in such appliances that it succeeds to work, although it is necessary in every part of a circuit, including the wires, which is what I shall be investigating. The standard abbreviation for electrical resistance is R and the symbol for and the symbol for ohms in electric circuits is the Greek letter omega, ?. Resistance is measured in ohms (?); 1 ? means that 1 Volt would be needed across the wire to drive 1 Ampere through it. 100 ? would require 100 Volts to drive 1 Ampere. So, in general, R= V or Resistance= Voltage I Current Closely linked with the topic of resistance is the resistor. A resistor is capable of controlling the amount of current within a circuit; regardless of whether you want to increase or decrease the current. Resistors are available in various forms but the simplest of them all is a thin conductible wire fixed into a circuit (as illustrated below.) If certain factors of a wire are changed, there are a variety of outcomes as shown below. ...read more.

Middle

This in turn means that the resistance of the wire has increased. A wire of longer length is more likely to have a higher resistance because the electrons will collide more often. How cross sectional area will affect the resistance of a wire I consider a wire whose cross sectional area is smaller would have a higher resistance. This then means that the 'cross sectional area of a wire is inversely proportional to its resistance'. I have come about this theory by the fact that a wire which has a greater cross sectional area would allow the electrons to flow more freely, thus decreasing the resistance. A wire whose cross sectional area is smaller would not allow the electrons to flow as easily because there is less room for them to move about, thus decreasing the current flow which means that the resistance has increased. A factor that would also increase the resistance of a wire, whose cross sectional area was smaller, would be that because the electrons have less to move about in they would also have a higher possibility of colliding. How temperature affects the resistance of a wire The higher the temperature of a wire the more likely it is to have a higher resistance. This means that the 'temperature of a wire is directly proportional to its resistance'. This is because as temperature increases the energy within the electrons also increase. This then means that the electrons move about more often which causes them to collide more often, thus resulting in a loss of energy in the form of heat. This then means that resistance has decreased. Overall I believe that copper will conduct electricity the best, this is because it is known to be the best conductor of electricity, after silver. Constantan is likely to conduct electricity second best because overall it contains 55% copper. This then leaves Nichrome as the poorest conductor out of the three. ...read more.

Conclusion

Evaluation After contemplating about how I performed in this investigation, I discovered that there was still room available for improvement, as there always is. After all science is about perfection. Generally I performed well in this investigation since at first I was having many difficulties trying to understand the SWG theory and all the formulae that I later learnt, and understood. Once I had got this aside and got a move on with the actual investigation, my results were accurate to a certain degree although not quite perfect. My first idea for improving this investigation would be to measure the results of all 9 wires 3 or 4 times. This way I would be able to construct very, very accurate results by taking the average of each wire and creating close to perfect graphs. The copper wires would require the most attention this time round because the results are fairly difficult to record precisely, but I did get them to a fairly good degree of accuracy. Alongside this I would change the difference between the results, it should be measured every 5cm instead of 10cm to make the results more accurate and this in turn would make more reliable graphs. The greatest alteration I carry out if I were to redo this investigation would be to have the actual experiment take place within a controlled environment this is because we had no control what so ever, over the temperature in the classroom/ lab, if it were a cold day we would have one temp and a hot day we would have another temperature. So the temperatures should have been fixed for each wire to make the test fairer. Generally I found the most difficulty when attempting to collect accurate results for the copper wires but other than that, I performed fairly consistently throughout the entire investigation. I feel, that alongside the improvements suggested above, some of which were out of my control, I would have been able to produce a far more accurate, not to mention reliable investigation. Daljit Malli 1 ...read more.

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