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SCIENCE COURSEWORK: RESISTANCE OF WIRE EXPERIMENT
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Risk Assessment To keep the experiment safe I shall keep electrical conductors away from the plug sockets. I will take care not to hurt myself or anybody else with the crocodile clips. I will also not turn the power socket on full so as that the wire does not burn or set fire to any surrounding objects or burn anybody. Preliminary work Firstly I assembled the apparatus as shown in the diagram below. For the wire I used 34 standard wire gauge wire. I then took measurements placed the two wire ends marked with an X...
Voltmeter reading by the Ammeter reading, giving me the resistance. This experiment would then be repeated three times so as to determine any anomalous results.

Diagram of apparatus for alternative experiment

I predict that the readings on the Voltmeter and Ammeter would be higher but when divided and the resistance worked out that the resistance would be very similar to that of the results worked out in my main experiment. This would be a useful experiment to carry out alongside my other to support my theory and satisfy my aim.

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INTRODUCTION: In this coursework... INTRODUCTION: In this coursework investigation, I will be doing a series of experiments to see how changing the length of a piece of wire affects the resistance of the wire. PREDICTION & BACKGROUND THEORY: I predict that as the length of wire becomes longer, the resistance will become gradually bigger. A piece of wire is made up of several hundred atoms. An electrical flow is able to run through the wire, these are e- electrons. As the current increases the velocity of the e- electrons increases which increases the amount of collisions between the electrons and the atoms. This, in turn, creates a higher resistance. We know that if the current increases, the resistance does too. There are three factors which can affect the resistance of a wire, these are the length of the wire, the material it is made of and the area of the wire. The structure of the wire is show below, it is similar to a lattice structure with atoms in rows, packed quite closely together. = Atoms = Electrons As we can see from the diagram, the electrons will have to work harder to make their way through the piece of wire. PRELIMINARY WORK: To make sure I have done my research and preparation work correctly, I will do a preliminary experiment. This is like a "test run" to make sure I don't run into any major problems. Should a problem become apparent, I will be able to change it before I start to record my results of the experiment for real. I will record my results, however, to see if they look correct and in the right range. METHOD: a Set up apparatus in the following way b Set up wire in the appropriate way. i.e. choose correct length and put crocodile clips either side of chosen length c Ensure ammeter is set to "0". d Switch on power supply e Record results f Switch off power supply g Alter length of wire h Repeat steps "b" to "g" for remaining length of wire SAFETY PROCEDURES: a Switch off power supply between readings b Ensure wires are connected t power supply correctly c Ensure wires are safe "“ i.e. not bare or broken ACCURACY PROCEDURES: a Measure a certain length of wire in more than one place to see if you get a similar reading. b Always start experiment with Ammeter at "0" c Switch of power supply to allow wire to go cool for all readings PROCEDURE FOR FAIRNESS: a Use same equipment for all experiments i. Ammeter ii. Volt Meter iii. Wire b Allow wire to go cold before taking next reading. Temperature could cause changes. RESULTS: Length in CM Voltage Average Resistance V1 V2 V3 In W 5 0.5 0.2 0.1 0.3 3 10 0.7 0.3 0.2 0.4 4 15 0.9 0.4 0.3 0.5 5 20 1.1 0.5 0.4 0.6 6 25 1.2 0.6 0.5 0.9 9 30 1.4 0.7 0.6 1.2 12 35 1.5 0.8 0.7 1.0 10 40 1.6 1.0 0.8 1.1 11 45 1.7 1.1 0.9 1.2 12 50 1.8 1.2 1.0 1.3 13 Current = 0.1amp Wire = Nickel Chrome ANALYSIS AND EVALUATION From the graph overleaf, we can deduce that our prediction was correct. As the length of the wire increases, the resistance does too. We have noticed that two points don not follow this trend. This could be due to a flaw in the experiment, such as "we left the power on too long and caused overheating" or "we simply took a mis-reading". However, this does not happen for the majority of the readings so we have an adequate set of results to draw this conclusion. The results could be changed if we did things differently a second time around: - Changed current - Used different wire - Left the power on for longer Our prediction has been proved correct. As the length of wire increases the resistance gets bigger. They are proportional to each other in this case.   

INTRODUCTION: In this coursework investigation, I will be doing a series of experiments to see how changing the length of a piece of wire affects the resistance of the wire. PREDICTION & BACKGROUND THEORY: I predict that as the length of wire becomes longer, the resistance...

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Aim:- We will investigate... Aim:- We will investigate the length of a wire in a series circuit, and if it will affect its resistance. Prediction:- Resistance is the force of which opposes the flow of an electric current around a circuit so that energy is required to push the charged particles around the circuit. I predict the resistance will vary with the length. I also predict the longer the wire the less current will flow which increases the resistance. This is because electric current is the movement of electrons through a conductor, so when resistance is high, conductivity is low. Therefore, the electrons will have to push their way through a shorter path of atoms in the wire, reducing their resistance. Whereas, if the length was longer, then the number of atoms in the wire increase. Electrons are negatively charged particles, and protons are positively charged atoms. Electrons move around, but protons don't move, they stay in the same place. Current is a flow of electrons, and is measured in amperes A. When a current flows through a resistance, energy is given off as heat. I think the thicker and shorter the wire, the lower the resistance. I think this because, for example, if you had a road with cars parked to the side and only one car at a time can pass the cars parked on the side of the road as the road is so narrow that allows two cars to go at a time, but as it seems that there are cars parked, that only one car can move past the parked cars; in this case it will be slower for the cars to pass, because the road is long and narrow. Whereas, if the road was wider thinker and shorter it would be quicker. DIAGRAM OF THE THICKNESS AND LENGTH Planning:- Before I do start my investigation I will need to set up my circuit. I will need a variable resistor connected to a power supply, an ammeter and a voltmeter voltmeter parallel to the nichrome wire. I will move the knob on the variable resistor into five different positions for each one length e.g:- 10cm, 20cm, 30cm "¦"¦.. I will get five different readings for each length, and I will be doing five different lengths, which makes twenty-five readings all together, on the voltmeter and ammeter. I will calculate the resistance with this equation:- V = R x I OR Potential difference volts, V = Current amps, A x Resistanceohm, This is how my circuit will look like when I've finished setting it up:- DIAGRAM OF CIRCUIT I will link all the components together with the wire connected to the circuit with crocodile clips at the length of 10cm. I will use to measure the voltage using a voltmeter and recording the results on a table. I will also need to measure the current using an ammeter and recording the results for them too. When I have the results I require, I will use the calculator and divide the voltage by the current to get the resistance. I know that I will need to turn off and on the power supply every time I investigate another length of the wire. This is because the wire intends to warm up and this may have an effect on my other readings and also the wire can snap in half by melting. To keep my investigation fair, I will keep the voltage on the power supply the same, the type of wire and the thickness, and also do the investigation in the same surrounding temperature. Analysing:- I have calculated the resistance of each length on the nichrome wire. I have used these results of values to plot a graph of resistance against length. Length goes along the bottom axis because it is the dependent variable. Its value depends on the length of the wire chosen The points on my graph are a little scattered, none of the points touch the line of best fit, but they are quite close together.. On my graph of the length against gradient, I have rejected one point. I would of rejected two, but I have noticed that the 10cm point was very high, I was going to also reject the 40cm point too, but I was more curious on the 10cm. my table of results suggests that the voltage reading for one point in the 10cm trial was very high compared to the other results of 20cm, 30cm, 40cm and 50cm. but I reckon that I must of miss read the meters whilst investigating. I have noted my working out on the graph of current against voltage. On my graph of current against voltage, there is an anomalies point which I have circled. It is the 10cm point of 0.90V and 0.18A which I must have rejected on the graph of length against gradient. So this is the reason of my rejection on the graph of length against gradient. You can see that this one point has affected the gradient. And as I mentioned that I must of miss read the meters.   

Aim:- We will investigate the length of a wire in a series circuit, and if it will affect its resistance. Prediction:- Resistance is the force of which opposes the flow of an electric current around a circuit so that energy is required to push the charged...

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A trolley is positioned the... A trolley is positioned the top of a ramp, the summit being Xcm from the ground. It is then released, rolling all the way down the ramp which is a set length, then comes in to contact with the ground and travels a distance of 2 meters before it passes a line. Once the trolley cleared the ramp we began timing, then once it reached the 2 meter waypoint we stopped the timer, by doing this we are able to determine the speed of the trolley. Based on existing scientific knowledge, I know that this experiment depends on a certain type of energy being converted into another type. When the trolley is raised to the top of the ramp, it gains a certain amount of gravitational potential energy. This is then converted into kinetic energy as the trolley moves down the ramp and reaches the ground. To see what factors may affect the way the experiment turns out, it may be useful to look at the formula for potential energy. P.E = MxHxG where m=mass, h=height and g=gravity Obviously, the more potential energy the trolley has got, the faster it will move down the ramp. So, theoretically, the only factors that can affect this experiment are the height and the mass. The gravity could be altered although we would have to travel to other planets which is far out of the schools budget, therefore the gravity will always stay constant: 1G. I will be investigating, by varying the height the summit of the ramp is raised off the ground. I will measure if the average speed increases or decreases. There will always be smaller forces that could slightly affect the result, such as friction between the ramp and the trolley's wheels, and air resistance. There is no way I can control any of these factors, but they shouldn't affect the results so much as to give completely anomalous readings for each experiment seeing as they remain a constant throughout the experiment. Planning When planning my experiment, I will need to take into consideration the following points: "¢ Safety "¢ Fair testing "¢ How many results I will take "¢ What range of variables I will experiment with "¢ Equipment Safety With this straightforward experiment there is not much that needs to be taken into consideration. No harmful substances are being used, neither are flames, solvents, or atomic-reactors. Although at the end of the 2 meter run way some sort of barrier will need to be placed to prevent the trolley from continuing its course and therefore thwart potential harm to any unsuspecting pedestrian. Fair Testing As with all scientific experiments, only one variable must be altered at one time. All the rest must remain constant to ensure good stable results. By using present knowledge, I know that the following factors can affect the outcome and must be controlled: Height of ramp. The height is the factor which I will be changing. This is included in the formula for potential energy. the height of the ramp should affect the speed of the trolley in some way. I will be changing this variable to do the test, it is my only variable. Mass of trolley. The mass is also included in the formula for potential energy and so could affect the speed of the trolley one way or the other. The mass will be kept the same throughout the experiment because we will be using the same trolley for all of them. Gravity. The gravity is the last portion of the formula for potential energy, which will affect the outcome if it is increased or decreased. The way to maintain this factor is to simply stay on the same planet and not to move the experiment area by to great a range gravity at equator less due to centrifugal force created by earths spin. Friction. As I mentioned that the only factors that should affect the outcome of the experiment would be mass, height and gravity. They make up the formula for the potential energy. But other factors may use some of this energy when it is being converted into kinetic energy as the trolley moves down the ramp. The friction between the wheels of the trolley and the surface of the ramp can consume some of the energy, also the friction between the axels and fixings, and the point at which the trolley makes contact with the ground will also cause friction. This can slow down the trolley, but only very slightly. To maintain the same friction for all the results we should use the same ramp throughout the experiment, and will not apply anything to the ramp or the wheels of the trolley. Air resistance. This is also a form of friction. There is very little we can do to control this factor, and its effects would be so insignificant it may not matter. Basically, we just need to make sure we have the same trolley and ensure that the surface area is constant. With these points in mind it is essential that we must keep the same trolley, use the same ramp and keep the mass constant. We will also have to keep the length of the runway the same. Ranges and amounts To make this investigation successful, we must choose a suitable range and amount of readings to record in order to come up with a useful set of results that are easy to plot a graph with and that make sense. For example, it would be pointless to experiment with heights ranging from 1cm to10cm because the trolley would not even reach the 2 meter waypoint. Instead a more sensible range, let's say from 10cm to 80cm, would be appropriate and should yield better results. We could take readings every 5cm, and take a minimum of three readings on each height to work out an average this makes sure that the end result more accurate. Therefore we will use the following variations in height the only variable we are experimenting with is height and it is the only value to be varied, everything else remains constant. 10cm 15cm 20cm 25cm 30cm 35cm 40cm 45cm 50cm 55cm 60cm 65cm 70cm 75cm 80cm Equipment To perform the experiment we will need the following equipment. Trolley "“ To roll down the ramp Ramp "“ For the trolley to roll down Meter Stick "“ To measure out 2 meter run way Chalk or some sort of marker pen "“ To mark the start and finish lines Stop Watch "“ To time the trolley Barrier "“ To stop the once it has reached the end of the runway Big metal thing with clamps on "“To hold one end of the ramp up and keep it stable From this experiment I expect to find out what factors affect the speed of a body when no manual force is applied to them i.e. pushing them. This experiment is being conducted to prove the potential and kinetic energy formulae which, once completed, can be used to calculate exactly the results of any situation using these theories. In fact, before recording the results I could use the formula to estimate what the outcome would be. Method The following is the method to the practical. it gives a step by step description of how we preformed the experiment. 1. Set up equipment ramp held up by metal clamp thing and measure 2 meters from the ramp marking off the 2 meter point and positioning the barrier. 2. Ensure the height of the ramp is the determined test height using the meter stick. 3. Position trolley at the top of the ramp 4. Release the trolley 5. Start the timer as the trolley makes contact with the floor 6. Stop the clock when the trolley reaches the finish line 7. Record the time taken for the trolley to reach the finish, next to the relevant height, in a table We will then record the results and proceed to raise the ramp another 10cm and continue the experiment, once we have attained a full set of results we will proceed to repeat the test another 2 times to give us the 3 tests needed to give a fair test. Prediction As I mentioned in the Introduction, the experiment is based on the potential energy at the top of the ramp being converted into kinetic energy at the bottom. I then deduced the following formulas by using my current scientific knowledge and attaining information from the internet. Potential Energy at the top = Kinetic Energy at the bottom Potential energy = work done Potential energy = weight x height lifted Weight in N = mass x 10 therefore: Gravitational P.E = Mass g height joules kg N/kg m I also found out some formulas to determine Kinetic Energy: K.E = ½ x mass x velocity squared K.E = ½mv2 Knowing this we can write: P.E = K.E Therefore mgh = ½mv2 The formula can be simplified by cancelling out the 2 m's and moving the ½ to the left side of the formula changing the x10 to x20, therefore we now have: 20h = v2 SQRT 20h = v SQRT = square root This formula will give us the average velocity for the trolley going down a ramp of h metres high. Once we have found this we can actually use the equation for average speed to find out how long it will take the trolley to reach the finish line and actually produce a theoretical result prior to conducting the experiment. Therefore this shows that the higher the ramp is raised, the higher the velocity of the trolley will be resulting in a quicker time to reach the finish line. I can also predict from this formula, that the shape of the graph v against h. As h increases, by 5cm each time seeing as this is how much we will increase our actually height by v will increase too, but not in proportion. This is due to the square root in the formula that we have to use to find v. The higher the height goes, the less gap there will be between the velocity of the present reading and the previous heights velocity reading. The graph should produce a curve. Therefore I can predict that the Increase in height of ramp = Increase in velocity of trolley. Results Height cm Time seconds 10 2.00 15 1.40 20 1.00 25 0.93 30 0.90 35 0.81 40 0.79 45 0.78 50 0.77 55 0.75 60 0.79 65 0.81 70 0.82 75 0.85 80 0.87 Height cm Time seconds 10 2.00 15 1.38 20 1.01 25 0.94 30 0.89 35 0.80 40 0.78 45 0.76 50 0.75 55 0.75 60 0.76 65 0.79 70 0.80 75 0.83 80 0.85 Height cm Time seconds 10 2.04 15 1.30 20 1.05 25 0.95 30 0.90 35 0.78 40 0.77 45 0.76 50 0.72 55 0.75 60 0.80 65 0.83 70 0.85 75 0.85 80 0.88 Average results i have also added a velocity column to the table I did not do this for the other ones because it would have taken too much time because we would be averaging the velocity values as well as the time values which would be easier to work out by getting the velocity from the averaged time values, and would not be needed because either way we get the average velocity, but this way is less time consuming. Height cm Time seconds Velocity M/S 10 2.01333 0.99338 15 1.36 1.47059 20 1.02 1.96078 25 0.94 2.12766 30 0.89666 2.23051 35 0.79666 2.51048 40 0.78 2.56410 45 0.76666 2.60872 50 0.74666 2.67861 55 0.75 2.66666 60 0.78333 2.55320 65 0.81 2.46914 70 0.82333 2.42916 75 0.84333 2.37155 80 0.86666 2.30787 From these results I have made a graph to show the curve of h against v Conclusion The graph has a few fluctuations but there were problems when the trolley hit the ground because it would lose some of its speed there, and the amount lost there was out of our control and not usually regular, so we tried to get the results as close as we could without better equipment. The curve in the graph is due to the increase in friction at where the trolley is hitting the ground, and along the ramp and ground which at some speeds slows the object down to a lower speed than objects dropped than lower heights; this is mainly due to the friction caused by the impact with the ground. I originally said that I could predict the outcome using the formula, but I never took in to account the friction caused when the trolley hit the ground, the formula would most probably predict the first few results seeing as they are not as greatly affected by friction as the rest. My prediction was proved correct as the graphs clearly show that the speed does indeed increase when the ramp is raised higher. This is due to the fact that more potential energy is given to the trolley as it is raised higher and height is part of the formula that makes up P.E: P.E = mgh P.E = mass x gravity x height So the higher an object is the more gravitational potential energy it gains. When it falls, its potential energy is converted into kinetic energy and since energy can neither be created or destroyed, only converted; it will move at a faster speed. So, to sum up, as you lift an object to a height the object gains gravitational potential energy. The higher you lift the object, the more energy you are using which is chemical energy to power your muscles and therefore the more potential energy the object is gaining. Potential energy is converted into kinetic energy completely so the object when released will move at a faster rate depending on how high it is lifted. The height does affect the speed at which a trolley travels down a ramp. The experiments went very well and ran efficiently, thanks to the plan we had drawn out beforehand. Although we had very limited time and were not able to produce any other results using different methods. Although the results did have quite a few inconstancies, this was due to many factors, firstly the impact point of the trolley hitting the ground, and secondly the timing was done by a human, and therefore is not completely accurate. I also tried some tests above 80cm to see what would happen, this eventually resulted in the destruction of the trolley, but the results did prove that the speed did decrease as it got higher due to the landing, and eventually at 100cm the trolley was unable to reach the end of the runway. These results I decided were not needed because they just prove that friction gets greater as the object increases in speed which I have already shown. If I were to do this experiment again, I would experiment with different surfaces of ramp, and better equipment, for example we could use 2 light gates for timing, one would be positioned at the start of the run and one at the end to completely automate the timing part f our experiment and help reduce error, also the computer would record the results for us and save time typing or writing them down. We could have also created some sort of curve at the bottom to prevent the extra friction caused as the trolley hits the ground, or possibly used a longer ramp and conduct the timing while the cart goes along the ramp therefore eliminating the landing stage completely also we could have made sure that the ramp was now leaning to a side which would encourage the cart to move to the left or right and lose time by travelling a longer distance. We could have also tried varying the mass of the cart, although the mass of an object does not affect the rate at which it falls as proven by the famous experiment done by Galileo which states that the mass of an object does not affect the rate at which it falls, and he proved this by dropping 2 balls of different weight off a tower and they both hit the ground at the same time. Although there may possibly be some variation in the speed due to friction because the greater weight would put more pressure on the wheels and put more pressure on the ramp therefore causing more friction, and also more friction at the point where the trolley hits the ground too. I will now test the formula and see how close our results were to the expected results. I will use the average table without the time because we will not need the time, only the speed seeing as the formula I am using does not calculate time. Height cm Velocity M/S 10 0.99338 15 1.47059 20 1.96078 25 2.12766 30 2.23051 35 2.51048 40 2.56410 45 2.60872 50 2.67861 55 2.66666 60 2.55320 65 2.46914 70 2.42916 75 2.37155 80 2.30787 Therefore the square root of 20x10 should give 0.99338 The actual answer is 14.14213 There is a significant difference, although I have not taken in to account the 2 meter distance and the friction it will cause and also the friction of the landing and the trip along the ramp, possibly if I do some more calculation we can work out how much energy the friction consumes. Predicted Velocity Height cm Velocity M/S 10 14.14214 15 17.32051 20 20 25 22.36068 30 24.49491 35 26.45751 40 28.28427 This would have been about the speed of the trolley as it reaches the bottom of the ramp, there is a significant loss of speed at the impact point and as the car moves along the ground, which is not as smooth as the ramp and also causes greater friction. If I combine the tables I should be able to see how much energy is lost to friction. Height cm Velocity M/S Calc. Velocity M/S Velocity lost due to friction 10 0.99338 14.14214 13.14876 15 1.47059 17.32051 15.84992 20 1.96078 20 18.03922 25 2.12766 22.36068 20.23302 30 2.23051 24.49491 22.25981 35 2.51048 26.45751 23.94703 40 2.56410 28.28427 25.72017 This shows that a lot of energy is lost to friction, if we would have improved the experiment by using a light gate and performing the experiment on the actual ramp itself we could have eliminated a lot of this friction, but not all of it because that would be virtually impossible, this experiment also shows me that friction has a much stronger effect on material than I had originally expected. If the results had been more accurate we could have worked out a formula for the amount of energy lost through friction, but our results would need to be very accurate to calculate this and we have run out of time and do not have the sufficient materials to do this.   

A trolley is positioned the top of a ramp, the summit being Xcm from the ground. It is then released, rolling all the way down the ramp which is a set length, then comes in to contact with the ground and travels a distance of 2 meters before it...

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