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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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Electromagnetism experiment: Introduction: I...Electromagnetism experiment: Introduction: I start the introduction with a question: Will increasing current in an electromagnet increase the power of the electromagnet? The electromagnet we will be making is a very primitive one compared to that of the complexity of modern electromagnets found in machinery, but the way it works is almost identical. Electromagnetic technology is extremely complex and because it is an electromagnet, the higher the current, the stronger it becomes, and with this an electromagnet can become incomprehensively strong. Such an example is that used in theme park rides to stop moving parts etc. these electromagnets are in fact so strong that when uncovered, if you were to stand with a spanner in your hand 10 metres away, it would pull the spanner out of your hand along with the rest of your arm! To understand fully how an electromagnet works read on"¦ Background information: When an insulated wire is wrapped around some form of iron, nickel or cobalt core, whether it be a nail or a u-shaped core, and then attached to a power supply it creates an electromagnet capable of picking anything from the size of a paperclip right up to anything as big as a car and bigger! Obviously such a primitive electromagnet would not be able to lift a car but a more advanced one would have no problem lifting a car. When the power supply is cut off the items picked up will fall off. This is because the current creates a magnetic field and this magnetic field is lost when it is turned off. When a current channels through an electromagnet a magnetic field is produced. This field is built up in a series of concentric rings. The diagram below shows a cross-section of a wire's magnetic field. As you come further away from the wire the field weakens and spreads further apart from each ring. There are four main factors that affect the strength and size of this field: Current/voltage Number of coils Size and shape of core Material of core iron being the strongest For example: two coils wrapped around the iron core would induce twice the strength of one coil. By this I mean that each coil will have twice the strength of one coil on it's own. Below shows a single coil's magnetic field. When two are present these rings become double the size creating a considerably larger and stronger field. Magnets are formed when certain substances iron, nickel and cobalt cool. Normally when a non-magnetic substance crystallises the atoms point in random directions. Now because of the properties of the aforementioned substances their atoms point in similar directions at each end of the magnet. These are called domains. This is because of the nature of the earth's gravitational field. Each side of the magnet's atoms, point in opposite directions. Each domain is known as either the south or north pole. Each end of the magnet is where the strongest part of the magnetic field coincides. The experiment in hand is simple. A piece of wire will be wrapped around an iron nail or some form of iron-based core where each end of the wire is attached to a circuit consisting of a power source and an ammeter. Our group will be testing the power of the magnet varying the power of the current around the circuit. We will be testing the strength from 0 to 5 amps. My prediction is that when the current is increased in turn so does the strength of the electromagnet. I believe this because an electromagnet needs an electrical input in order to create a magnet, so logically if that electrical input is increased then it becomes stronger. The aim of this project is to test the power of an electromagnet when the current is increased or decreased. Preliminary experiment The initial experiment is just to test the strength by seeing how many nails are picked up at varying strength of current. We will also be testing the strength when the amount of coils are increased or decreased. Apparatus: Crocodile clip x 2 Red insulated wire x 2 Black insulated wire x 1 Ammeter U-shaped iron core 1: An electrical wire will be coiled around a soft-iron core 30 times. 2: Crocodile clips will be connected to yellow connecting wires at each end. 3: These together with the ammeter will be connected up to the power supply as shown in the circuit diagram. 4: A fixed amount of nails will be poured over the electromagnet with the power switched on 5: The power will be turned off. All of the iron filings that drop off will be weighed. I will vary only the current in this experiment. All other factors will be kept constant. I will measure the amount of iron filings at 1,2,3,4 & 5 amps. I will repeat each experiment three times for accuracy. Safety Precautions We will make sure that there is no bare insulation or any water near any electrical equipment to prevent electrical faults and dangers I might need to repeat some results that show no correlation to the other results, if they are drastically wrong. Factors Affecting The Experiment: 1:Current-This will change in one experiment. This will be kept constant by observing the ammeter and correcting any fluctuations on the D.C power pack. 2: Magnetic strength of the Soft-Iron Core. This will affect the power of the electromagnet. It will be kept constant by using the same soft-iron core. 3: The way in which the wire is coiled. If the coils are coiled towards end, then one end will be more powerful than the other, and affect the results. I will try to keep the shape of the coils uniform. 4:The way in which, the nails are shaken. The harder the magnet is shaken, then the more nails will be dropped, and the more the results will change.   

Electromagnetism experiment: Introduction: I start the introduction with a question: Will increasing current in an electromagnet increase the power of the electromagnet? The electromagnet we will be making is a very primitive one compared to that of the complexity of modern electromagnets found in machinery, but the...

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Aim: To investigate the heat... Aim: To investigate the heat loss of the insulating materials, bubble wrap, cotton wool, blanket and foil Introduction: I will carry out this investigation by measuring the temperature of hot water in beakers insulated with these materials. Naturally the insulated beaker with the warmest water will have prevented the most heat loss. To understand how materials prevent heat loss I need to look at the three ways in which heat can be transferred or lost to the surroundings. One of the ways is conduction. This is when heat energy is transported along an object from the hotter region to the cooler region. The object itself does not move. So when an object is heated, its atoms start vibrating with the heat energy. The free electrons begin to diffuse through the object and collide into other electrons transferring kinetic energy. Substances that have particles close together, like metals are good conductors. Meanwhile gases have particles that further apart so they are poor conductors. Therefore things that are made of particles that are not close together, are poor conductors but good insulators such as gases. Another way is convection, which only happens in liquids and gases. This is when heated particles start moving faster so they move further apart. The heat also makes the particle expand so they become less dense than the unheated particles. As a result of this, the heated particles rise upwards taking the extra energy with them and are replaced by colder and denser regions. A form of convection is in evaporation where the particles in a liquid keep bumping into each other. Sometimes they collide with each other with kinetic energy. During these collisions some particles receive so much energy that they can break away from the liquid. The final way in which heat can be lost is through radiation. This is the transfer of heat energy by waves. Every object sends out infra red radiation but hotter objects send out more. This is completely different to conduction and convection as it does not require particles, so the so infra-red radiation can pass through a vacuum. Also dull and black surfaces emit more heat while shiny and white surfaces emit less. However this makes black and dull surfaces better absorbers Prediction: With the kinetic theory on mind, I predict that out of the materials of foil, bubble wrap, wool and blanket the bubble wrap will be the better insulator. This is because the bubble wrap has a lot of air trapped in its pockets. Air is a very good insulator as its particles are widely spread out therefore there is a less chance of them colliding and passing energy on. This means that there will be less energy transferred to the surroundings, as the bubble wrap would prevent heat loss mainly through conduction. Furthermore the material is made from plastic which in itself is a good insulator. As the aluminium foil is shiny it will reduce heats loss through radiation by reflecting heat back in, like a flask. However since it is a metal, some heat will be lost through conduction. Naturally the blanket material would be a good insulator as its purpose is to keep people warm. This because it has lots of layers and like the wool has air trapped between it fibres. So by reducing heat loss through conduction it should be a good insulator but not as good as the bubble wrap. This is because as it is a dull and black colour some heat will be lost through radiation. The cotton wool is also material that has a lot of trapped air in between its many fibres. Even though it is a good insulator, I feel that because of the thinness of the material the bubble wrap will still be the better insulator. All these materials except the foil are lagging which are insulating materials that have tiny air pockets that trap air to prevent heat from being conducted away. Safety: Since I am dealing with very hot water there are precautions I will need to take. Firstly I will abide to the general laboratory rules i.e. tidy workspace, loose clothing tucked away, and safety goggles. When I need the water for my experiment I will my teacher to pour the hot water. Preliminary investigation: For my investigation I need to know at what intervals I should record a temperature reading and for what period of time. Here are the results of my preliminary investigation: Time Secs Temperature °C 0 84.5 30 80.5 60 77.0 90 75.5 Time Mins Temperature °C 0 84 1 80 2 74 3 72 These results show that taking the temperature readings at 30 second intervals would make the results more accurate and to do this over a 5 minute period. I will also use 80 ml of boiling water and make sure all starting temperatures are the same. Range of results: My results will fit into a table like this, TIME SECS TEMPERATURE OF WATER IN BEAKER ºC CONTROL WOOL BUBBLE FOIL BLANKET Apparatus: In my experiment I will use the following equipments: Electric Kettle "“ To boil the water 5 Beakers "“ To hold the hot water for the experiments Aluminium Foil Bubble Wrap Cotton Wool Blanket Thermometer "“ To measure the temperature Stopwatch "“ To time the experiments Elastic Bands "“ To hold the materials in place Variables: In my experiment the volume of the water for each beaker will be 80 ml. Temperature readings will be taken at 30 second intervals for 5 minutes and I will make sure all beakers have the same starting temperature. Therefore there will 10 readings after the starting temperature. This will ensure my test is fair. The only thing that will be different is the material around the beakers. Method: First of all I will wrap four of the beakers in the materials with the elastic bands. The other beaker will stay uncovered as it is the controlled experiment. After placing the thermometer into the beaker, the 80 ml of water will be poured in and the stopwatch will be started straight away. Also the starting temperature recorded. After that the temperature reading will be recorded at 30 second intervals shown by the stopwatch. This will be done for 5 minutes and repeated for all the beakers. Results: TIME SECS TEMPERATURE OF WATER IN BEAKER ºC CONTROL WOOL BUBBLE FOIL BLANKET 0 83.0 83.5 83.0 83.5 83.5 30 80.5 80.0 81.5 79.5 80.5 60 77.0 78.0 80.0 77.5 78.5 90 75.0 76.0 78.5 76.0 76.5 120 73.5 74.5 76.5 74.0 75.5 150 72.0 73.5 75.5 73.5 74.5 180 70.0 72.5 74.5 72.5 73.5 210 69.0 71.5 74.0 71.5 72.5 240 68.0 70.5 73.0 70.5 71.5 270 66.5 70.0 72.5 69.5 71.0 300 65.5 69.5 72.0 68.5 70.5 Observations: For all the materials there is a sharp drop in temperature for the first minute and after that it gradually slows down. The starting temperatures for the insulated beakers are very close but at 5 minutes they the end readings are more spread out. As you can see on the graph the bubble wrap has the most gradual curve and consequently the slowest rate of heat loss. From the starting temperature of 83.0 °C, it dropped by 12.0 °C after 5 minutes. The blanket is the second best insulator with the temperature drop of 13 °C from a starting temperature of 83.5 °C. The cotton wool lost 14.0 °C from a starting temperature of 83.5°C The aluminium foil is the worst insulator from the materials as from a starting temperature of 83.5 °C it lost 15 °C The controlled experiment the beaker with no insulation has the steepest curve and therefore the fastest heat loss. From the starting temperature of 83.0 °C, it lost 17.5 °C after 5 minutes. Conclusion My prediction was correct as the bubble wrap material was the best insulator because it prevented the most heat loss being the best insulator. The bubble wrap was the best insulator due to its ability to reduce heat loss through conduction. This can be understood by looking behind theory of conduction. Since heat is energy associated with the motions of the particles making up a substance, it is transferred by these motions, shifting from regions of temperature, where particles are more energetic to regions of lower temperature. The rate of heat flow between the two regions is relative to the temperature difference and the heat conductivity of the substance. In solids the molecules are bound and add to the conduction of heat mainly by vibrating against neighboring molecules. However a more important mechanism is the migration of free electrons. Materials such as metals have a high free-electron density therefore they are good conductors of heat while non-metals do not conduct as well. Since gases and liquids have their molecules even further apart they are generally, very poor conductors which makes them good insulators. Therefore the bubble wrap which is made up of lots of air pockets has not only less free electrons to transfer heat but it has molecules the trapped air that are quite far apart. This makes harder for heat from the boiling water in the beaker to be conducted away through the bubble wrap and to the surroundings The blanket and cotton wool were also quite good insulators as they too have a lot of air trapped between the fibres. The foil was not as good because being a metal it had more free electrons with particles being closer together, for heat to be conducted away to other regions. However, since it was quite shiny it reflected some heat back in, to the beakers, such as the effect of a flask so it prevented heat loss better than the controlled beaker. The controlled beaker naturally let out the most heat since it had no form of insulation except the fact that it the beaker was made out of glass which in itself is a fairly good insulator. Evaluation The method that I used to carry out my investigation was fairy simple to carry out. It required me to pour out 80 mls of hot water into beakers insulated with different materials. The temperature of the water was then recorded over a 5 minute period at 30 second intervals. The results of my investigation were accurate as I took my readings at eye-level to the nearest half a degree centigrade. I had no anomalous results and the accuracy can be seen on my results graph where the readings are close to the best fit curve. However I could have been even more accurate as if the time h d been available tome, I would have repeated my experiments to get an average of the results. Another way in which I could have improved my experiment was if was available to me, I would have used a data logger with temperature probe. This would have given me very accurate readings every second. I could have also used polystyrene lids to reduce heat loss by convection in the beakers. To extend by investigation I could have used different beakers like copper cans to see how the material of the beaker affects the rate of heat loss. In addition I could look at the effect of the amount of layers of material insulating the beaker as well as looking at different volumes of boiling water.   

Aim: To investigate the heat loss of the insulating materials, bubble wrap, cotton wool, blanket and foil Introduction: I will carry out this investigation by measuring the temperature of hot water in beakers insulated with these materials. Naturally the insulated beaker with the warmest water will have prevented...

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