Physics Coursework Essay Example for Free

Physics Coursework Essay This systematic method was followed in the experiment to ensure accuracy and precision. Firstly fill a Pyrex beaker with 250 ml of water after washing the beaker. Construct the circuit as shown in figures 5 and 6 securing the thermistor with crocodile clips. I will use a mild abrasive paper to clean metal oxides from the connections to ensure there is not sufficient oxide build up to affect results. It is essential to make sure the thermistor is positioned centrally near to the thermometer suspended from the retort stand. The voltmeter should be set to measure voltage between 0-2V, which should give a sufficient scale. The stirrer speed should then to be set to ensure sufficient stirring but does not create a whirlpool effect. Then turn the hot plate on and begin taking temperature and voltage measurements at every 2i C. It is necessary to ensure that the experiment is conducted in a controlled manner and the thermometer is read with the users eyes looking directly at the reading in a level plane thus preventing parallax errors. The readings should be taken from 20-80 i C and recorded. After this random readings should be taken to find the temperature according to the calibration curve and then the actual temperature should be found using the thermometer and the readings compared. Results Table: Temperature i C Potential Difference/ V Run 1 Potential Difference /Random Measurements I heated the water using the normal apparatus in the standard way. Using Calibration curve 2 (reasoning explained later) I was able to use the voltage read out to work out the temperature of the water. At: Potential Difference /V Calculated Temperature From Calibration / i C Actual Temperature /Analysis: I have achieved all of the following results using the equipment stated. The two calibration curves have the general logarithmic properties as generally expected when using this set up. Firstly, I feel it necessary why I have discounted one calibration curve. Firstly I have not ignored the results from run 1, they are perfectly reasonable and fair. The only reason to have a slight reservation about the first set of the results came about when inspecting the equipment after the first experiment. It came to my attention that around the battery a rust/ acid layer had formed on the connections of the battery pack. This was then swapped for an identical battery and pack to produce the results for run 2. Run 2 gave similar results but there were far less anomalous points on the graph and nearly all points fell on the line. I believe the slight corrosion on the battery may have produced these slightly anomalous points on run 1. Also a major reason for choosing run 2 as the calibration curve is that on the random measurements the predicted temperature fell within i 2. 0i C, which I considered a good result. The gradient on both graphs are fairly balanced in that moving on down the curve the gradient did not decrease rapidly unlike the typical calibration curve described in Figure 4. This will be discussed in the overall evaluation of the sensor. Evaluation: The experiment has thoroughly tested the sensor and has proved that it is capable of doing the job what it is intended to do but some improvements need to be made. The gradient of the calibration curve is such that even at the upper limits of the sensor it has a relatively good resolution in that it can distinguish between temperatures like it did at the lower limits of the sensor. The thermistors published response time is 1. 2 seconds. It did respond very quickly to temperature change however, this fast change may not be needed in such a large volume of water that will not change temperature very quickly at all. In a hot water tank also there would not be a stirrer like in my experiment (which I felt it necessary to use to calibrate the thermistor) and thermal equilibrium would not be reached and therefore if the sensor were to be used in a hot water tank it would be necessary to consider the best position for the sensor. Alternatively a number of thermistors could be positioned all over the tank and the average temperature taken. Run 1 was not a failure, it simply showed systematic drift. The same trend was shown as in Run 2 however; the curve was closer to the X- axis. To conclude this project, I believe I have fulfilled my aim and have designed a sensor to measure the temperature inside a domestic hot water tank. The sensor may have to be re-engineered slightly to cope with the un-uniform heating inside the tank as described above. I also believe that for the sensor to work a battery would not be suitable as a power source. The battery would loose energy over time and for this sensor to work it is calibrated on the assumption that the batterys energy is not lost over time. Therefore giving a false temperature reading meaning that the sensor is rendered useless. It would be more suitable to use an adaptor from the mains converting the alternating current to direct current and also stepping down the voltage. In the lab I used a battery however, simply to test the sensor and this experiment has proves successful and shown that the thermistor could show the user the temperature of hot water inside a tank with sufficient resolution between 20-80i C. Instrumentation Coursework David Burgess 12 RJF Page 1 of 9 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.