Investigating Resistance Essay Example for Free

Investigating Resistance Essay Plan of Action I am going to find out what affects the resistance of a wire by using a six volt power supply in order to have a sufficient charge that wont be too strong or too weak, also so the wires wont get too hot very quickly as it would then greatly affect our results. Five different thickness of nichrome wire as well as changing the length. I will use 20,24,28,32 and 36swg and for each one I will record the voltage and the amps for the lengths from 100cm, down every 20 to 20cm. Do this by setting up the equipment as shown in the diagram below and change the wire after you have recorded all the results for the previous wire, doing so for each one: We will then use the results to find the resistance which is: R=V Resistance = Volts I Amps I will then record our results on a graph. After that I will do the same thing but record all the wires at 60cm three times to do an extra graph comparing cross-sectional area and resistance. Trial run Below is a results table showing our first trial run of our plan of action so we can see if anything needs changing. The wire used was nichrome-24swg. LENGTH (CM) V VOLTS I AMPS R RESISTANCE V2 I2 R2 V3 I3 R3. The results do prove my prediction correct but to show it accurately I will change my plan of action to going down in 10cm rather than 20cm. This will give me a wider range of results. Improved Plan of Action I am going to find out what affects the resistance of a wire by using a six volt power supply, five different thickness of nichrome wire and the changing of length from 100cm, down every 10 until I get to 10cm. The thickness that I will use are 20, 24, 28, 32 and 36swg. For each thickness I will record the Volts and Amps from 100cm down to 10cm. I will do this by setting up a circuit like the one below and changing the wire after I have recorded all the results for the previous wire: I will the use the results to find the resistance for each length of each wire using this equation: R=V which is . Resistance = Volts R Amps I will then do the same as the above but only record all the wires at 50cm three times to compare cross-sectional area and resistance. Then Ill do the graphs. Apparatus . Power supply, to supply the charge for the wires. . 5m of nichrome wire, for the charge to travel through. . crocodile clips, to connect the circuit. . wire cutters, to cut the wire down to the desired lengths. . metre stick, to measure the different lengths of wire. . connecting wires, to carry the electric current. . ammeter, to record the amps. . voltmeter, to record the volts. Fair Test I will make sure it is a fair test by using the same bit of wire when we record the 50cm three times, letting the wire cool down before moving on to the next length because heat creates more resistance, use the same amount of power for each wire so there are the same amount of electrons passed into the wire each time. Also I will make sure the circuit is connected properly at all ends. Method . Set up equipment as shown in diagram. . Cut a 20, 24, 28, 32, and 36swg nichrome wire to 100cm using a metre stick. . Start at 20swg and add it to the circuit. . Start at 100cm record the results and move the crocodile clip down 10cm. . Record the results from the ammeter and the voltmeter onto a table. . Move the crocodile clip down 10 more cms and so on until you get to the end. . Change wire to the next gauge and gradually work your way through all of them. . Repeat the 24swg three times at all lengths. . For all the thickness record the results three times at 50cm. . Then find the resistance using the equation R=V/A . Plot the graphs. Safety Box . Make sure bags and coats are in a safe place where nobody can fall over them . Walk in an appropriate manner around the laboratory. . Leave the wires to cool before touching them . Do not take water near the power pack and dont have the voltage too high Results Nichrome-20swg Length (cm) V volts I amps R resistance Nichrome32swg Length (cm) V volts I amps R resistance Nichrome-36swg Length (cm) V volts I amps R resistance Evaluation My results show that the longer a wire is, the higher the resistance will be and the thicker a wire is, the lower the resistance will be. This is what I predicted and it has been proved. The resistance in a wire depends on its shape and size. The scientific reason as to why thin wires have a higher resistance than thick wires is that the sea of electrons that flow throughout a metal all travel through at the same time and if the electrons have a larger area to travel through then there will be more space for them to flow freely with less collisions that cause loss of energy, but if they try to flow through a thin piece of metal they will collide into the other ions creating heat which then creates more resistance. Longer wires have more resistance than shorter ones because a short wire has a certain amount of resistance, now if you double the length of the wire then you will also be doubling the resistance. This is because there is a greater distance for the electrons to travel through so there is a greater amount of resistance slowing the current down. The graph comparing length and resistance shows a linear trend, but I think we may have made an error in the experiment. I think this because the line for the 32swg wire is above the line for the 36swg wire when they should be the other way around. I suspect that we may have used the same wire accidentally because the points for each result are so close, but generally speaking the theory is proved because all of the others have followed the expected pattern of an increase of resistance, in the increase of length and the increase of thickness. The graph comparing cross-sectional area with resistance shows that with each increase in width of a uniform nature, the resistance drops, but by a greater amount each time, i. e. 32swg-10 28swg-5 diff-5 24swg-2 diff-2 20swg-0. 9 diff-1. 6 If I was to do the experiment again then I would improve my method by being more accurate with my measurements of the wire. The problem with the measurements before was that the wires were very bendy and hard to straighten out so as a result the wires would have been longer then the actual length recorded, so I would use straight wire and would make sure it was cut to the nearest mm to get more accurate results. Overall I am quite pleased with my experiment. The results were generally successful and prove my prediction and the theory correct. If I could do it again then I would make sure I had all the correct wires for each experiment, and that the wires werent too hot as to affect the results in a major way by creating too much resistance. I would do this by leaving a longer period of cooling time so the heat will escape and the resistance will drop. There was two anomalous results on the graph comparing length and resistance. The reasons for these could have been an accumulation of not holding the crocodile clips at the right places, e. g. At 50cm instead of 60cm, or the connections that sent the current through the wire may have been held on tighter on one of the distances resulting in a stronger current and less resistance, and loser on the next resulting in a lower current and more resistance.