Investigate_the_Variation_of_the_Resistance_of_a_Thermistor_with_Different_Temperatures

Physical Science Unit Title: The scientific Method for Investigation BZX 831 Assignment 1 Investigate the variation of the resistance of a thermistor with different temperatures Aim: For this experiment I am going to investigate the variation of the resistance of a thermistor with different temperatures. The resistance will be tested at approximately every 5 degrees, with a range from 80 c down to 25 c, and these results will be recorded. After recording the results, the experiment will be repeated at a total of three times, so we can get an average that should be correct and accurate. Theory: I predict that when the temperature of the thermistor is increased the resistance will decrease. Equipment: Thermistors T4 Thermometer C5 Multimeter (M4 – resistance) Multimeter (M3 – temperature) Kettle Beakers (1. hot water 2. cold water 3. empty) Ice Method: First I set the multimeter to KΩ , unit for resistance. Next I will fill the beaker with boiling water from the kettle. Then place the thermometer into the beaker, to check the temperature. If the temperature is around 85 c then I will place the thermistore into the beaker. Before placing the thermistor into the beaker, I will take a reading of the room temperature and its resistance. Once the thermistor is placed I will start to take the readings from the thermometer for temperature and the multimeter for the resistance. I will take the reading every time when the temperature drops by 5c. To speed up the experiment I will use cold water to drop the temperature quickly because it's very time consuming when you let the temperature to drop by itself. Another thing I have to take in account is that when I add cold water I have to thoroughly make sure the water is stirred to keep water at the same temperature, otherwise the water around the thermistor will be at a different temperature, to that around the thermometer. I will end the experiment by taking the last reading of 25 c and I will do this experiment three times. Then from the three results I will find the average. To get an accurate reading on the thermometer which is going to be used, the depth of water must be at least 6cm, therefore I need at least 6cm of water in my beaker to avoid inaccurate thermometer readings. To make sure the experiment is as safe as possible we need take a few safety precautions. Wearing safety goggles until all practical work and clearing up is finished. Making sure that nothing is on the floor is also very important in case of an emergency. Results: Room temperature was at and the resistance was Temperature (T)/C | Resistance (R)/ | Ln ( T) | Ln (R) | Absolute Temp Ta=T+273.15 | Reciprocal Temp (1/Ta) | 1 | 2 | 3 | AV | 1 | 2 | 3 | AV | | | | | 80 | 79 | 79 | 79.3 | 38 | 39 | 39 | 38.7 | 4.37 | 3.66 | 352.45 | 1/352.45 | 75 | 75 | 75 | 75 | 40 | 41 | 42 | 41 | 4.32 | 3.71 | 348.15 | 1/348.15 | 70 | 69 | 70 | 69.7 | 45 | 46 | 48 | 46.3 | 4.24 | 3.84 | 342.85 | 1/342.85 | 65 | 65 | 65 | 65 | 55 | 56 | 57 | 56 | 4.17 | 4.03 | 338.15 | 1/338.15 | 60 | 60 | 61 | 60.3 | 65 | 66 | 66 | 65.7 | 4.1 | 4.19 | 333.45 | 1/333.45 | 55 | 55 | 55 | 55 | 77 | 77 | 78 | 77.3 | 4.01 | 4.35 | 328.15 | 1/328.15 | 50 | 50 | 50 | 50 | 93 | 93 | 94 | 93.3 | 3.91 | 4.54 | 323.15 | 1/323.15 | 45 | 45 | 46 | 45.3 | 112 | 112 | 113 | 112.3 | 3.81 | 4.72 | 318.45 | 1/318.45 | 40 | 40 | 41 | 40.3 | 135 | 136 | 137 | 136 | 3.7 | 4.91 | 313.45 | 1/313.45 | 35 | 35 | 35 | 35 | 168 | 169 | 170 | 169 | 3.56 | 5.13 | 308.15 | 1/308.15 | 30 | 30 | 30 | 30 | 205 | 206 | 207 | 206 | 3.4 | 5.33 | 303.15 | 1/303.15 | 25 | 25 | 25 | 25 | 259 | 260 | 263 | 260.7 | 3.22 | 5.56 | 298.15 | 1/298.15 | Temperature of ice water Temp | | | | | | 12 | 465 | | | | | 6 | 603 | | | | | 4 | 662 | | | | | 3 | 708 | | | | | 2 | 755 | | | | | 0 | 880 | 903 | 922 | 928 | 930 | Temperature of boiling/hot water Temp | | 98 | 22.5 | 98 | 22.6 | 98 | 22.5 | 98 | 22.6 | 98 | 22.6 | 98 | 22.5 | Dependent and independent variables The in dependent variable is the variable that is 'independent' – it doesn't depend on anything else. Independent bariables are factors that can affect the final outcomes of the experiment. We are also capable in changing these variables in order to produce the conditions required for the experiment and it's also called the input variable. Dependent variable are the outcomes of the experiment which can not change, but instead are affected by the independent variables and it's the 'result' or output variable from our experiment. In the case of our experiment, we chose to vary the temperature, and see what happened to the resistance, so the temperature is the independent variable, and the resistance was the dependent variable. Evaluation: In my experiment, the thermistor was quite good which gave accurate results. Date size limits the precision with which a measurement can be made. Taking an average over repeated measurements can improve the final result, as long as the conditions can be kept the same. Systematic error is very hard to detect, because detecting it means making another, even better, measurement. Systematic errors include zero error, and error due to disturbing influences, for example temperature. I think the thermistor could have been better by having a high resolution, appropriate output for a given input, rapid response time, small unsystematic fluctuations in results, and a small systematic error. Soemtimes it is necessary to reduce the sensitivity so that the measuring instrument can deal with larger changes of input. Analysis: From the graph I can see that as the temperature increases the resistance decreaces. My prediction says that the resistance will decrease with an increase of temperature I can now verify that with the help of my results and graph. Conclusion As you can see from the results, as expected the resistance produced by the thermistor decreases drastically as the temperature increases. This is because the seminonductor material of the thermistor becomes more conductive as the temperature increases. In conclusion, I think the results and the graph supported my prediction. Assignmet 3 Calibration is the set of operations that establish, under specified conditions, the relationship between the values of quantities indicated by a measuring instrument and the corresponding values realised by standards.