Resistance of a wire Essay Example for Free

Resistance of a wire Essay We undertook an experiment to find the relationship between resistance and a length of wire. Equipment: Variable resister, Wire 1m long, Digital voltmeter, Digital ammeter, 4 X 1. 5 cell, 1m ruler, Connecting wires. Method We collected our equipment needed and set it out as the circuit diagram below. I started by drawing out my results table to record my results on. The headers for the columns where as follows: Length (cm), Current (A), Potential difference (V) and Resistance (I). At every 10cm we took a reading and entered it into our table. Some flickered between two values so I took both down. Starting at 1m and working down. On the second experiment I started at 10cm and worked the other way to see whether it affected the results. When using the variable resistor we kept it on the minimum resistance throughout the experiment. While taking the results we had more than one result for the current and potential difference, which in turn caused some results to have more than one resistance value. Because of this I had to alter our table slightly during the experiment to ensure we took down all the results. To ensure the test was as fair as possible I repeated the test to ensure the experiment was fair and true. Looking at my results in the table they are very similar which proves that it was fair. Results These tables show my results from the experiment and the sum for: V I R First experiment: Length (cm) Current (A) Second reading for (A) Potential difference (V) Resistance ? (I) Second result for (I). Second experiment: Length (cm) Current (A) Second reading for (A) Potential difference (V) Second result for (V) Resistance ? (I) Second result for (I) Third result for (I) Fourth result for (I) I have drawn graphs for these results: see appendix a and b. Analysis My results show that the resistant relates to the length of the wire used. As the current increases the potential difference does and the resistance decreases. As the length of wire is reduced the potential difference reduces and so does the current. There is a slight difference between our first and second experiment. Both graphs show that there is a definite pattern but there are some anomalies. The anomalies seem to be separate from the other results. But this anomaly happened on both experiments on 60cm. There may be some other reason for this. I cannot see why it should happen on both sets of results at the same measurement. Both graphs are similar and follow a very similar line. Graph A shows quite a straight line with only one less extreme anomaly where as graph B show a reasonably straight line with one major anomaly which stand out considerable from the rest. On both graphs the results take a wavelike form rather than a straight line. The results do to an extent follow Ohms law. On graph A, 4 of the plots run on the same line, which agrees with Ohms law, and graph B 4 plots do the same. The second graph started at a lower current and potential difference but I think it should be higher because of the use of the wire before which could have increased the temperature. On the second experiment there was more flickering on the ammeter and voltmeter, which caused the increase in the results. Although the flickering occurred it was constant. On table 1 the potential difference decreased in shorter stages that table 2. When plotting my results on a graph I had to take an average from my results. Conclusion Current id the flow of electrons around the circuit this is pushed by voltage. The resistance tries to oppose it. This is apparent from looking at our experiment results. The resistance stays constant as long as the component does not change its physical condition i. e. The wire does not get hot. George ohm was the first scientist to investigate this theory. The resistance is measured in Ohms Resistance at a constant temperature is proportional to potential difference. The relative size of the voltage and resistance decides how bit the current will be. By increasing the voltage more current will flow but by increasing the resistance the current is less. This is shown in our results. Our results agree with the theory. 100cm of wire = little current but a lot of P. D = lots of resistance 10cm of wire = lots of current but little P. D = little resistance This shows the longer the piece of wire the more resistance Wires of different material have different resistance: Copper wire I Steel wire V The graph shows above that cooper wire has a low resistance and is a good conductor. Steel has a higher resistance and a lower conductivity. Both wires have the same potential difference (voltage) across them. Wire A. I Wire B Wire C V As you can see above different wires have different resistance. Evaluation There were a few problems that occurred in our experiment such as the flickering of the ammeter and voltmeter, which caused us to have to take more than one result. On both graphs there was an anomaly on 60 cm. There may be some other reason for this. Both graphs are very similar and follow a very similar line. Graph A shows quite a straight line with only one anomaly where as graph B show a straight line with one major anomaly which stand out considerable from the rest. On 60cm the potential difference increased on both sets of results. The temperature of the wire was not taken to see whether it had increased in temperature during the experiment. It does not show increased resistance on the second table, which was taken straight after the first experiment, which could have affected it. By taking the temperature of the wire on the same resistance for a period of time we could see how long it takes for the temperature to increase and in turn for the resistance to increase. This could help with evaluating our results and also time the experiment to see how long the wire had current flowing through it and then if it had increased in temperature. The results are reasonably reliable because the do to an extent obey Ohms law. I think the reason for the unreliability could have been because the wire had changed its physical condition (got hotter). To further our investigation we could go on and use a longer piece of wire 2m and also use different types of wire such as steel and copper. Change the temperature of the wire because wire that is colder is a better conductor. I believe our results were reliable but need improving by the suggestions I have given above. Bibliography Hodder and Stoughton AQA GCSE Physics Class notes   CPG Revision and Practice Guide Alison Eatock GCSE Physics 30/11/03 Resistance of a wire 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.