Resistance coursework Essay

My Investigation: I choose to do a nichrome wire because during my preliminary work nichrome shows more resistance compared to nickel and copper wire. This is because the electrons collide with the material of the nichrome wire. Measurements: The things I will have to measure are: the volts and amps and on each interval I take to take readings. I will have to take 5 reading of each volts and amps, so I can work out the resistance, and then I will have 5 resistance readings, from this I will work out an average resistance. Also I will be measuring the wire from 100cm down to 10cm. Diagram: This is how I will set up my circuit: There are particular factors that we have to keep the same in order not to alter the correct results.   Do not alter the positions of the devices during the experiment.   Make sure the total length of wire is exactly 1m.   Record the current and voltage accurately, using the correct units. Always place the crocodile clips on the right measurement.   Before you start the experiment, test the devices being used. If any are faulty, change them.   Leave the power pack set at the same voltage for the whole of the experiment. The surrounding room temperature must be kept, otherwise the particles in the wire will move faster (if the temperature increases). Therefore, this will have an effect on the resistance.   The wire along the metre ruler must be straight and exactly 1m long. Bends in the wire may affect the resistance. The reading of the voltage should be taken promptly after the circuit is connected. This because as soon as a current is put through the wire, it will get hotter. I want to test the nichrome wire when heat is affecting it the least. Safety: This experiment is not too dangerous but it could be if not handled with caution and care. Make sure that the electricity is off at the plug socket when connecting and altering the circuit.   Be careful of any sharp edges on the crocodile clips or on the wire cutters or on the wire once cut. If you cut your self make sure you wash the wound and see a medical nurse if needed. If a fire breaks out switch off the power and use a near by fire extinguisher that is not H2O (because of the electricity) to safely stop the fire.   Make sure the coils in the resistance wire don’t touch and short circuit because this will ruin the experiment and may heat up the wire and catch fire. Do not set the power pack voltage to more than 2V. This is a safety hazard.   If you smell burning, promptly switch off the power pack from the mains.   Make sure that when the power pack is switched on, the near by taps are switched off. If there is any water spilt near by the sockets or surrounding areas, wipe it before you start the experiment.   Make sure the power pack cable or the conducting wires aren’t frayed. Reliability and Accuracy: Reliability: I can rely on my results because I have taken 5 different readings and then taken an average. This is so if one of my results goes wrong then I have four other ones to compare it with so I know if a result is abnormal. I am using an Ammeter to get an accurate current reading and not relying on the approximate readings on the power packs variable controls. Accuracy: I will coil the wire so that there are no short circuits in the wire. I will do this by spacing out the coils and checking it regularly throughout the experiment. This is because if the wire does short-circuit then you will be measuring the resistance of the length of that short-circuited piece of wire and not the whole length of wire. I will also take the reading on the voltmeter as soon as possible so the heat does not affect the resistance. Obtaining My Evidence: During the investigation, I changed the length of the wire by 10cm to see if it affects the resistance and the amount of current I was going to use. Initially I had decided to use 2 amps but I changed it to 1 amp because I felt by using a low current I may not get a very good reading voltage and resistance. The Analysis: Explanation of results- As the length of wire increased, the current decreased. As the length of constantan wire increased, so did voltage. Resistance increased as the length of wire did. The longer the length of the wire, the higher the resistance because of the amps. The current flowing the p. d. across it providing the temperature is constant. V=Ii R or I=V/R or R=V/I From the graph which I have produces I conclude that the higher the length of the wire the higher the resistance. The thin wire in 1 amp tends to resist the movement of electrons init. We say that the wire has a certain resistance to the current. The greater the resistance the more voltage is needed to push the current through the wire. The resistance is calculated by Resistance-P. d across the wire/Current through the wire (1) I conclude that as the length of a wire doubles, the resistance also doubles (provided the thickness of the wire is kept constant0. I also conclude that as the cross-sectional area of the wire doubles; the resistance halves (provided the length of the wire stays constant. I conclude this because my graph shows that resistance is inversely proportional to 1 (thickness2) so the theories behind these conclusions are: As the length doubles the resistance doubles. Resistance is caused by electrons bumping into ions. If the length of the wire doubles, the electrons bump into the ions twice as much so the resistance will double. In my investigation I found out that as the length of the wire increased the resistance and voltage increased as well. The only thing that decreased was the current. I think this because the resistance and the voltage has no longer a distance to travel so more volts/amps are needed where as the current has a shorter distance to travel each time so as the same amount of amps are being used they are building up more. From the graph that I have done, I have found a pattern. This pattern draws me to a conclusion that the higher the length of the wire the higher the resistance. I had also stated this in my prediction, in the earlier stages of my experiment, so this means that my prediction was correct. The thin wire I (amps) a lamp tends to resist the movement of electrons in it we say that the wire has a certain amount of resistance to the current. The greater the resistance the more voltage is needed to push a current through the wire. The Ohms law calculates the resistance of a wire by: Resistance (R) = potential difference across the wire (V) Current through the wire (I) There is a resistance in a wire because the electrons bump in to each other in the nichrome wire. So the high resistance is because of the high length of the wire and because of the electrons bumping in the wire. My predictions match my results because I predicted that resistance would increase as the length of the wire increased and that is what happened. I worked it out by using my head. I started to think about this experiment then I thought that the current would have a longer distance as the length increased and that would make the resistance longer. I also found out that the resistance of one amp carries a current of one amp if there is a potential difference of one volt across it. Judging from my results, I can safely say that the majority of my prediction was right. The resistance did change in proportion to the length of wire. This is because as the length of wire increased, the electrons that made up the current had to travel through more of the fixed particles in the wire causing more collisions and therefore, a higher resistance. A thinner wire also means more resistance. Resistance is known to be inversely proportional to the cross- sectional area (diameter). I. e. if the diameter is increased, the resistance decreases. A wider wire means less chance of the free electrons having collisions into atoms and losing energy. Another point of my prediction was that as the length of wire doubles so does the resistance. This proved to be true. I can show this in my graph. The straight line indicates it. I can also see these in my results. E. g. 30cm=0. 95? and 40cm=1. 124 ?. The theories behind these conclusions are: As the length of the wire doubles, the resistance also two folds. Resistance is caused by electrons bumping in to ions. If the length of the wire doubles, the electrons bump into the ions twice as much so the resistance will double. I also want to state the fact that as the length of a wire doubles the resistance also doubles, however providing the thickness of the wire is kept constant. I conclude that, as the cross sectional area of the wire doubles the resistance halves providing the length of the wire stays constant. Evaluating my Evidence: I believe I carried out my investigation very well. I used all the equipment I was supposed to. I set the experiment correctly. Most of my results are accurate. I managed to get reading off both the volt meter and ammeter for each length five times and I used the correct safety precautions. I believe most of my results are accurate. Not all of the readings are correct as at the end the wire got very warm and gave faulty readings. After studying my results, I realise there is one anomalous result. It occurs in the voltage on the sixth voltage. It looks as if the volt meter had some interruptions such as the heat of the wire or the heat of the surrounding area. However this did not affect my predictions as I predicted the longer the wire the higher the resistance and this is what had happened but it had less resistance for that particular one than I had expected. It did not alter the increasing pattern in resistance. I believed that my investigation and the results are mainly accurate because my investigation was carried out very well. I believe that if I had to use my results as evidence I think they show that the longer the nichrome wire the more resistance and the shorter the less. I assume this because my graph shows at 10cm of nichrome wire there is 0. 592(ohms) and at 100cm of nichrome wire there is 2. 386(ohms) there is a difference of 1. 794(ohms) which proves longer the wire the more resistance. I can prove that my experiment was successful because of the graph I drew. It showed length of wire against resistance. If I had to further improve my investigation I would carry it out again and I would do it with a much longer piece of wire at a higher current. If I had to do this experiment again I will probably measure the wire every 5cm’s instead of 10cm’s to make sure it’s accurate and use a more accurate volt meter to get the best and accurate results. . I could also investigate how the diameter of a wire affects the resistance. An extra investigation I can carry out or perform to receive more proof and evidence would be to investigate and look into is the thickness of a wire and evaluate or match up with the length of the wire. Also I could examine if the specific metal materials or properties makes a change in the resistance. 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.