To investigate a factor which will affect, the resistance of wire Essays

To investigate a factor which will affect, the resistance of wire Essays To investigate a factor which will affect, the resistance of wire Essay To investigate a factor which will affect, the resistance of wire Essay Aim: to investigate a factor which will affect, the resistance of wire.There are four different factors we could choose to vary:-1. Thickness/diameter of the wire2. Length of wire3. Material of wire4. temperature of wireWe decided to change the factor length because it allows us to get continuous data in a large range. It is also the easiest to vary. I decided against Diameter of wire because it is hard to compare to resistance (they cannot be plotted against one another because as resistance goes up the thickness goes down), I also decided not to vary the material the wire is made of because it would give us discrete data which is hard to analyse. Temperature is a very bad variable because it is so hard to control; the circuit will increase in temperature whatever I do, so I need to take that into account.RESISTANCEResistance is anything in the circuit which slows the flow down. We know that Length affects this because as length increases so does resistance. Ohms Law, Potential Difference (V) across a conductor is directly proportional to the current (I) flowing through it, providing the temperature is the same.R=V/I resistance= voltage/currentResistivity: p=RA/lResistivity=resistance X cross section of the wire / length of wirePRELIMINARY REULTSWe did a short preliminary experiment to see how the resistance affected the temperature of the wire, when we put one crocodile clip at 0mm and one at 100mm the wire got so hot it began to burn and give off smoke. From this preliminary experiment we decided not to take any measurements under 100mm because it could become unsafe.RANGE OF RESULTSWe have decided to take results at 100mm, 200mm, 300mm, 400mm, 500mm, 600mm, 700mm, 800mm and 900mm we shall take each measurement twice. This should give us a wide enough range of results to plot on Graphs we will also re-do any anomalous resultsPREDICTIONI predict that as the length increases so will the Resistance because Ohms law states that potential difference is directly proportional to current and the current will increase as the length of the wire increases because there will be more resistance on it (it will be more spread out, current is carried by electrons in metals)SAFE TESTTo make sure everything is safe whilst carrying out the experiment safety goggles must be worn and the wire must not be touched while current is flowing round it and shortly after because it will be hot.FAIR TESTTo make sure the investigation is fair, we will use the same equipment each time, monitor the temperature (if the wire start to give off smoke we will stop and give it time to cool down to reduce anomalies) and we will measure our wire using a micrometer to check the width before doing any equations.EQUIPEMENTPower pack, to power our experiment so current flows through the wire.Ammeter, to measure the current flowing round our circuit.Voltmeter, to measure the voltage of our circuit.1m Nicrome Wire, to test.Wire, to put, our circuit together with.Metre rule, to measure the lengths of wires.Crocodile clips, to hold wires in place.DIAGRAMMETHOD1. set up apparatus as above2. Put crocodile clips at 0mm and 900mm3. Turn power pack on4. record Current and Volts5. Turn off Power pack6. Repeat steps 1-47. Repeat steps 2-6 but with 800mm.700mm, 600mm,500mm,400mm,300mm,200mm and 100mmWe can clearly see my results are correct because the constant is constant. To make our results accurate we used the same equipment each time, kept an eye on the temperature(When the wire started to give off smoke we stopped and give it time to cool down to reduce anomalies), we used digital a digital ammeter and voltmeter to reduce human error and we measured our wire using a micrometer to check the width before doing any equations. The width was 26mgs which is : 0.45 mm.ANAYLSISWe can clearly se that our graph supports our prediction, As the length increases so does the resistance, this tells us that Length and resistance are directly proportional. We can now work out the resistivity of the different lengths of wire:100mmResistivity=0.785 x 0.45100Resistivity=0.00353200mmResistivity=1.49 x 0.45200Resistivity= 0.00335300mmResistivity=2.11 x 0.45300Resistivity= 0.00352400mmResistivity=1.34 x 0.45400Resistivity= 0.00151500mmResistivity= 1.055 x 0.45500Resistivity= 0.00095600mmResistivity= 0.88 x 0.45600Resistivity= 0.00066700mmResistivity=0.81 x 0.45700Resistivity= 0.00052800mmResistivity=0.71 x 0.45800Resistivity=0.00040900mmResistivity= 0.62 x 0.45900Resistivity= 0.00031EVALUATIONOnly one anomalous result was obvious whilst carrying out our investigation (at 700mm) so we went back and did it again. Unfortunately when looking at my graph it seems there were more anomalies, I have circled them in the table and on the graph. I think the anomalies may have occurred because our battery pack broke and we had to get a replacement. Apart from the battery pack everything else went safely and well. Our preliminary experiments allowed us to make sure the wire did not get too hot which meant we did not get any anomalies around 100mm and that we were safer. I think our range was big enough but if we had more time I would have liked to done another repeat and possibly take measurements at 50mm intervals to achieve a greater range of results.I thought our results were really good they clearly supported our prediction that as length increases so does resistance. If I was to further this experiment I would use different metals and see which had the best resistivity, I would not use a metre rule because it was easy for human error to occur as it was not particularly detailed perhaps a digital measuring device would have been better. I might also try a different variable such as diameter of wire to see how that affected the resistance. Overall I was very pleased with our investigation and think that we did all we could to do it well.