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Energy conversion practical

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Energy conversion practical

  1. 1. Energy Conversion PracticalIntroductionWhen energy is used to do work, it usually changes into a different form of energy. Thisexperiment is about electrical energy converting into thermal energy. An example od electricalenergy converting into thermal energy is when water is heated on an electric stove. The energyused to start the oven is electrical energy. During the process of boiling water, the electricalenergy becomes thermal energy. According to the law of conservation of energy, the initialenergy should equal final energy. In this experiment, the initial energy is electrical energy and thefinal energy is Thermal energy. Thus, the amount of electrical energy should equal the amount ofthermal energy, although this was not true in this experiment because of random errors. In thisexperiment the formula VIT was used to find electrical energy, and the formula mc(delT) to findthe thermal energy (delT = change in Temperature). The efficiency was calculated using theformula Efficiency= 100% (output)/inputThe output is the thermal energy and the input is the electrical energy. The efficiency was offbecause of random errors. The time that the water boils and the Temperature of the water are theonly variable. The mass of the water, specific heat constant, voltage and current are all constants.The primary goal of this experiment is to determine the efficiency of converting energy from anelectrical form to a thermal form. The efficiency was expected to be very close to 100%according to the law of conservation of energy.Design Research Question: What is the efficiency when electrical energy is converted into thermal energy? Independent Variable: the time the water is heated up for Dependent Variable: the temperature of the waterControlled Variables: 1. Mass of water 2. Voltage 3. Current Description: A hot plate was plugged into an outlet and had 230.0 V and 4.0 A. A beaker of water was placed on the hot plate; the mass of the water being 96.39 g. A thermometer was inside the beaker, which was held in place by a retort stand. The hot plate was turned on and the time was recorded via a continuum and processed into a computer.
  2. 2. A Picture of The Experiment
  3. 3. Raw Data Time (± 0.5 sec) Temperature (± 0.5 °C) 0.0 31.0 30.0 37.0 60.0 42.0 90.0 47.0 120.0 53.5 150.0 61.0 180.0 70.0 Processed DataEfficiency = 100% (output)/input Output = thermal heat Thermal Heat = mc(delT) delT = change in Time Input= electrical energy Electrical energy= VITEfficiency= 100% (mc(delT))/ VIT) delT/t = slope of the Temperature/ Time graph= .2101c= 4.1813 m= 96.30 g± .01 delT/ t= 0.2101 ± .0001 C I= 4.0 A±.1 V= 230.0 V±.1 T= Sample Calculation Efficiency = 100% ( delT/T){(96.30) (4.1813)}/ (230.0) (4.0) Efficiency = 100%(.2010) {(96.30) (4.1813)}/ (230.0) (4.0) Efficiency = 43.8% * the uncertainty is too small too make a difference or change the answer Conclusion In a perfect world with no errors the efficiency of the conversion of electrical to thermal energy should be 100% because the thermal energy should equal the electrical energy. Taking into account random errors the efficiency should have been in the range of 90%- 100%. The results for the efficiency were extremely inaccurate at 43.8%. A conclusion that can at least be drawn from the experiment is that although efficiency is supposed to
  4. 4. be 100%, it will almost never quite reach that number because of random errors, whichare results of an imperfect world. By evaluating the slope of the graph, one can see thatthe relationship between the change in Temperature and time is linear and that the slopeof the graph of Temperature versus time can be substituted into the derived equation ofefficiency (100% (mc(delT))/ VIT) for delT/ T. Without the slope of the Temperatureversus time graph efficiency would be very difficult to calculate.Evaluation of Random ErrorsThe experiment’s results were quite different then what they were expected to have beenor than what they should have been according to the law of the conservation of energybecause if both energies are equal the efficiency result equals 100%. The inaccuracy islargely due to random errors.1. One random error that happened in this experiment was a loss of some of the mass of water when it was heated because some of the mass was evaporating. A difference in mass would affect thermal energy and thus would affect the efficiency results. To fix this a piece of cardboard or thick material could be place over the beaker to prevent evaporation. A whole would have to be poked into the cardboard just small enough so that the thermometer could be inserted in.2. Another random error was trying to measure the change in Temperature as related to time. At first, this was tried by measuring specific times and temperatures separately but this affected the results because the starting Temperature was different each time and measurements were affected by the previous experiments, and it was hard to calculate. To fix this a continuum was used so that the temperature and time could be related in a graph and the change in Temperature divided by the time could be measured by taking the slope. This also led to better accuracy and precision.3. The last random error was when someone held the thermometer to measure the temperature of thewater, it was unstable and difficult to get an accurate reading in a short time. To fix this a the thermometer was attached to a retort stand.

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