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GCSE: Electricity and Magnetism
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will be more particles within the wire to resist the movement of electrons, this is what is explained in the diagrams below: Wires ... 1. and... 2. With wire 1 being twice as long as wire 2 I believe that the electrical current passing through wire 1 will have twice as much resistance as it would be in wire 2. My belief behind this is that because the wire is twice as long there should be twice as many particles within the wire than wire number 1 therefore twice as much resistance is given.
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Because some of the energy is wasted as heat and sound. The amount of kinetic energy at the end is always less than the amount of potential energy you had to start with. This means that the ball will not bounce up as high, and therefore not have as much potential energy as it started with. Prediction: In this investigation I will investigate the percentage energy loss when a ball bounces. The variables that could affect the amount of energy lost are: * The height the ball is dropped from.
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If there is a potential difference (Voltage, V) across a conductor, a current (Amps, I) goes through it. But when you apply the same potential difference across different conductors, the currents are different. For example, if we put a potential difference of 230V across a kettle and toaster, the current in the kettle is 10A, whereas the current in the toaster is only 5A. The current is smaller in the toaster so it must have a higher resistance. Resistance is measured in ohms (?) and has this definition: "The resistance of a conductor is the ratio of potential difference applied across it, to the current passing through it" So the formula for resistance is: Resistance, R = Potential difference across the conductor, V (volts)
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The definition of voltage is the difference in electrical potential between 2 points. E.g. A terminal in a Cell. Voltage, basically you get the opposite results to current. Resistance is measured in Ohm's ? The resistance of a wire is affected by these 4 factors, the material, length, cross-sectional area and density. A resistor is a conductor designed to let a certain amount of electricity directly proportion to the current or voltage. Facts taken from textbooks and internet. Information I got of from the internet and books which states what resistance is. Ohm's law states that the amount of current flowing in a circuit made up of pure resistances is directly proportional to the electromotive force impressed on the circuit and inversely proportional to the total resistance of the circuit.
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* When we increase the temperature of a material the positive ion cores begin to vibrate more vigorously. This also makes it harder for the electrons to pass by, increasing the resistance. So resistance increases with temperature. The wire that we are using (constantan) is an alloy it shows very small changes of resistance with temperature. (Researched in Physics for today). However according to Ohms law the resistance of a metal is the same whatever current is flowing - provided the temperature doesn't change, so temperature change must be considered. * The length affects the resistance of a wire, because the electric current has further to travel along the electrons * Ohms law states that if the cross
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Prelim Work Before doing this experiment I did some preliminary work. I found a computer program called 'Focus On Science'. In this program it is possible to do a simulation of the test, to see what the results might be. In this test I used copper wire instead of nichrome wire. Although it was not entirely accurate, it helped show how I would set up the equipment and gave me some experience. According to 'Keith Johnson's Physics For You', as the length of wire increases, the resistance increases. This is fairly straight forward, as obviously if the wire is longer, the electrons will have to travel further, therefore being more exposed to ions and electrons in the wire, slowing it down.
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All of the values for current were found to be under 0A. I also found that in the main experiment, I will need to make sure that when I am investigating resistance in a short length of the wire, I need to keep the current at a low value, otherwise I will burn and melt the wire. This is because a short piece of wire has a low resistance, letting a large current flow thought it, making the wire overheat. I have decided to investigate resistance in the following lengths of wire: 3,5,15,28 - Some random numbers to see some changes in resistance in between the main lengths.
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To make this experiment be a fair experiment, I will do the following things. 1, I will put all my experimental equipments in the box, so that I can use the same equipments every time, such as battery packs and pencil lead. 2, I will do the same thing three times, and I will make sure that I finish every time I started because it would be some physical changing to the equipments if I left them there. Apparatus: For this experiment, I need a battery pack (4 batteries), a switch, and a set of wires, an ammeter, a voltmeter, 2 crocodile clips and a pencil lead.
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I think that the length of the wire will be proportional to the resistance increase. So if the length doubles the resistance should also double, because the longer the wire is the more room there is for these reactions to take place. If this is true my graph should look like this: I did a pilot test to find out which wire would be best to use out of Iron, Nichrome and constantan. During the pilot I found out that it is important not to let the wire over heat, so if I want to get fair results I will need to keep the voltage low.
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Factors The resistance of a wire depends on certain factors. Some of these variables are listed below: � Length of wire � Diameter or thickness of wire � Temperature at which wire is kept � The material of which the wire is made out of � The potential difference or voltage � Humidity � Cross sectional area � Voltage across circuit I will be investigating the diameter of a wire and how it effects the resistance. All the other factors will have to be kept constant whilst doing the experiment to ensure that the investigation is a fair test.
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We will also repeat each set of readings, and, in the event of a difference in result, we will take the average. Background Knowledge In any electrical component, there will be a resistance value, this value changes in accordance with the following variables * Length of wire * Temperature of component * Surface area of wire * Material of wire In theory, any of these variables can be investigated. However the only practical area to vary would be length as this is relatively easy to change. Whereas keeping various constant temperatures would be extremely difficult in a school laboratory situation.
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Plan I am going to do an experiment to investigate if the length of a wire effects the resistance of a circuit Safety I will have to a make sure there that I take some safety precautions before I do this experiment like the usual do not sit down while doing the experiment wear safety spectacles and a lab coat make sure the area is clear and there is no water about as we using electricity.
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I will do this about 10 times for one thickness in this case I have chosen 0.21mm. Then I will test different thicknesses for e.g.: 0.19mm, 0.32mm....etc. I will only take one reading for each thickness at a specified length for e.g.: for 0.19mm the length I will record will be 50cm, for 0.32mm 50cm as well and so on. I will use this to determine whether or not there is a relationship between area and the resistance. SAFETY I will have to consider this as I am experimenting with electricity, so: Although it is obvious I will also have to be careful when cutting the nichrome wire, making sure I don't get the pliers ends onto my fingers!
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to ke ke= 1/2 mv^2 ke= kv^2 ke x v^2 h x v^2 The equations shown above prove that kinetic energy will increase or decrease with the potential energy. But it also that once the ramp has reached its critical angle, the rule h x v will no longer work. Equipment: A ramp longer than 1.5 metres A metre ruler A stop clock A car trolley Six blocks with a height of 10cm Diagram: Trolley Stop Clock Ramp Metre ruler 6 Blocks Method: We need to find out the different times, it takes a trolley, to travel a length of 1.5 metres, from different heights.
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Flow of electrons around the circuit is called an Electric Circuit and it can be measured by using Ammeter. Electric current is measured in Amps. In a Series Circuit the current readings A , A , A are all the same proving that current does not get used up by components (the bulbs) in circuit, but flows through each one in turn. In a Parallel Circuit the current A splits up into A and A which then join up to give A where A =A +A =A .Again this proves that current does not get used up. If an Electric Current flows through a Coil of Wire a magnetic field is Formed Around The Coil creating an Electromagnet which is a magnet that can be switched on and off.
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I then recorded the corresponding voltage reading that was displayed on the digital voltmeter. I repeated this procedure using different lengths ranging from 30-100cm and adjusting the variable resistor until 0.2A was flowing through the circuit. After recording the corresponding voltage readings for each length and tabulating them I decided to repeat the whole experiment again another 2 times so that I could take the average voltmeter reading for each length. Using a micrometer screw-gauge I measured the diameter of the wire at 3 different positions along the wire and then calculated its average diameter from the 3 values.
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We see that if the area of the wire doubles, so does the number of possible routes for the current to flow down, therefore the energy is twice as spread out, so resistance might halve, i.e. Resistance 1/Area. This can be explained using the formula R = V/I. Diagram: Plan: Step1: Set up equipment as shown on diagram Step2: Draw a table to keep results as shown below Length of Wire (cm) Voltage (volts) Current (amps) Resistance (ohms) 100 90 80 70 60 50 40 30 20 10 0 Step3: Start experiment Step4: Work out the resistance using R=V/I Step5:
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electrons in the outer shell of their structure, as a result the outer electrons are able to move about freely even in a solid (shown below). Within the metal atoms there are free electrons, it is these free electrons which provide the conductivity of metals. The free electrons have to move in order to provide the current (shown below), the slower they move, the more the resistance, the faster they move, the less resistance. Therefore, if the wire is long then that means that the free electrons have to travel further, they have to dodge more metal atoms-this slows the speed of their movement, and so the resistance increases.
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We concluded firstly that voltages over 6 volts and short wire lengths (under 25cm) caused overheating, and resulted in the wire snapping. We had earlier decided that the length of wire would be the easiest factor to vary, but to get a wide range of results we would need to take measurements over a small scale, at for example 5cm gaps. Finally, after trying various types of wire we decided that a relatively thick 36 chrome nickel wire would be best, due to it's durability and resistance to breaking. Method We decided that to obtain enough, reliable results we needed to take readings from lengths of wire from 30cm to 100cm, at 5cm intervals (15 results in all).
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As the current increases, so does the temperature of the conductor, because the electrons moving through it faster. And as temperature increases so does resistance because it will make the particles in the wire vibrate faster as they are being hit faster and more often. It makes it harder for the electrons to get past the particles because they are moving more. Just like it is harder to cross a motorway than a normal road because the cars are moving faster. This only applies to metals; non-metals have the opposite affect, when they are heated resistance decreases. The Cross sectional area will affect the resistance as well because as the area increases the amount of particles increase as well and so do the amount of gaps between them.
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It is essential to use a low voltage because it means a low current that will not heat up the wires. If a high voltage is used the energy would be in form of heat which would make the experiment unfair. The investigation will be done at room temperature. The temperature cannot be investigated because it is hard to control the range of temperature needed without the correct apparatus. 2) Length of wire The larger the length of the wire, the larger the resistance.
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Resistance Electricity is conducted through a conductor, in this case wire, by means of free electrons. The number of free electrons depends on the material and more free electrons means a better conductor, and there is less resistance. For example, gold has more free electrons than iron and, as a result, it is a better conductor. The free electrons are given energy and as a result move and collide with neighbouring free electrons. This happens across the length of the wire and, in this way, electricity is conducted.
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Then to extend my research I am going to rap a second layer of fur on and a third with three layers of fur, I also will try a can with no fur to see if that makes any difference. So in total I am going to do four experiments and do them three times each to make it a fare experiment, and to see if I may have recorded an anomal result. I predict that the fur will trap air, and therefore reduce the heat lost by conduction.
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My graph should show that the length is proportional to the resistance. Plan: We will measure out some pieces of wire to 20cm, 40cm, 60cm, 80cm and 100cm. We'll then attach a crocodile clip to each end and connect it up to the circuit.
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What is Resistivity? Resistivity is a way of measuring the resistance in a material. To find the resistivity you have to find the resistance of the material in a length of 1m and cross section of 1m2. This means you can compare the resistivity of different materials to clearly see which has the highest resistance per metre of length. For this experiment I shall be using Constantan wire which has a resistivity of 4.9 x 10-7 ?m Variables * Temperature, resistance increases with higher temperatures.
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