Resistance of a wire Essay Example for Free

Resistance of a wire Essay Fair Testing Definition Fairness implies that the outcome of the activity truly depends on what is being investigated, and is not being distorted by other external factors. Therefore a fair test is one where all the variables are kept constant or the same, except the variable that is being investigated. A variable is anything that can change and which may influence the outcome of the investigation. List of variables   Length of a wire.    Temperature of a wire. Resistivity of a wire.   Thickness of a wire. Person that measures the length.   Person observing the metre readings. Number of variables.   Position of the variable resistor needs to stay constant.   Number of times you do the experiment to get the average.   Apparatus needs to stay the same, so you need to do it on the same day. Statement of fairness To make it a fair test, I am going to keep all the variables the same, except the length which I am going to change. I am going to take the measurements of the voltage and the ammeter readings. Range of Measurements to be taken (for the variable being tested) I will take the ammeter and voltmeter readings of different lengths. The different lengths will be in 10cm increments, from 0cm to 100cm. Experimental Procedure Apparatus: 1. 2 Batteries 2. Voltmeter 3. Ammeter 4. Metre ruler 5. Variable resistor 6. Rheostat 7. 1m wires mounted on a metre ruler 8. Crocodile clips 9. Connecting Wires Diagram: Method: When I set up the apparatus as the diagram above, I will put the slider in the middle of the variable resistor and I wont change its position throughout the experiment. I will get a metre ruler, which has wires mounted on it. I will get the crocodile clips and put one of the clips on 0cm and the other clip on 10cm. I will read the voltmeter reading as well as the ammeter reading. I will then take the other crocodile clip from 10cm and put the clip on 20cm. I again will read the voltmeter and ammeter readings. I will do the same for 30cm, 40cm. 100cm. I will repeat the experiment 3 times so the experiment will be a fair test. Safety Precautions I have thought about the safety precautions and I dont think there are any precautions to take. The wire could get hot if the voltage was too high, but in this particular experiment the voltage is supposed to be low. Results. Results Table Experiment 1 Experiment 2 Length of a conductor (cm) Voltage (V) Current (I) Resistance (? ) Voltage (V) Current (I) Resistance (? ) Average Resistance (? ) Results (trends or patterns of observations) From my table you can see that as the length of the conductor increases the resistance and voltage also increase but, the current decreases. Each time the length of the conductor doubles the resistance more or less doubles as well. The average is only really useful when the voltage and current are about the same. If the numbers are not around the same figure the average wouldnt really mean anything. It wouldnt be a true reflection on the other results. Conclusion In the planning part of this investigation I predicted that as the length of the conductor increases the resistance will also increase because the electrons will have more cations, the electrons will find it harder to go from one side to the other side. From my results table you can see that as the length increases the resistance will also increase. When the length goes from 40cm to 80cm, the resistance goes from 3. 96to 7. 95 The reason it happens is that in my theory I stated that the length of a conductor is similar to the length of a hallway. A shorter hallway would allow people to move through at a higher rate than a longer one. Resistance in wire depends on how thick and how long it is, and what it is made of. The thickness of the wire is called its gauge. The smaller the gauge, the longer the wire. Calculation of the percentage errors from the graph Experiment 1 Experiment 2 Length (cm) Voltage (V) Current (A) Resistance (? ) Voltage (V) Current (A) Resistance (? ) Average Resistance (? ) Line of Best Fit Difference % error Evaluation How accurate was the investigation? I think the investigation was quite accurate because I repeated the experiment 3 times and the results in the results table were all close to each other. The replicates are close to together, which means I could calculate a representative average. The apparatus was accurate because I had the right amount of everything I needed. However, if the connecting wires were a bit thinner than it would have been an even more accurate investigation. Overall I think the accuracy of the apparatus was good enough for this particular experiment because it is standard and the majority of the schools in England also use this apparatus. I dont think that the method could have lead to any inaccuracies, because everything was more or less accurate. The line of best fit looks perfect and there arent any anomalous results. Was this a suitable procedure? It was a suitable investigation because I got what I expected and it proved my prediction. Also, a lot of people done this investigation like this because it is good. My graph is also good, so I know the suitability of the investigation is positive. Was the evidence sufficient to support a firm conclusion? Yes, because if you look at my graph, it was done to a good degree of accuracy. As the length doubled, the resistance also doubled, so it was reliable. Also the % of error was less than 5. 00% all the time. The replicates are close to the average. I got what I wanted because I did some research so I knew what to expect. How could the investigation be improved? Improvements I would do the experiment more time to get a better average. I would do the investigation 3 times which would mean I could do it on 3 separate graphs with the same apparatus. I would also use a longer wire from 1m to 2m. Further work After doing this investigation, I could investigate another variable such as resistivity (type of wire). I would do the experiment by doing the following; 1. I would set up the apparatus. 2. I would cut 30cm of copper, tungsten, constantan, nichrome and steel wire. 3. I would measure the voltmeter and ammeter readings. 4. I would calculate the resistance. 5. I would repeat the experiment 3 times to get an average voltage and an average current. 1 Show preview only The above preview is unformatted text This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.