| 1.2 The thermometer | |
| The definition which we have given of temperature is of little practical value as it is not possible to measure the energy of each particle to find the average value. Fortunately, bodies have observable properties which vary with the temperature. The effects of the variation of the temperature of a body on some of its characteristic magnitudes, like its length, its volume or its electrical resistance in the case of a conductor, are well known. | |
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It is this circumstance which is taken advantage of in order to make a thermometer, making the value of the magnitude used, called thermometric, coincide with the corresponding temperature. In this way, in the familiar mercury thermometer the height of the column of mercury is made to correspond to the temperature, or in the case of digital thermometers an electric circuit is used in which the electrical resistance is very sensitive to variations in temperature. |
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In the following visual we initially present three identical thermometers: one of them is set at 0ºC (the temperature at which water freezes); another thermometer is set at 100ºC (boiling point for water). The third thermometer is set at a temperature of To, from - 10ºC to 100 ºC, which can be selected by the user. Using control T we can choose the temperature of the device with a constant temperature, thermostat, into which we will put the thermometer to measure its temperature; using the corresponding control we can put the thermometer in the thermostat or not. A fourth control, H, permits us to see the height of the column of fluid when the thermometer is in the thermostat. |
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| Heat and temperature | ||
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Carlos Herrán- J.L. San Emeterio |  |
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Thermal energy, temperature, heat | |
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Defining concepts | |
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The thermometer | |
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Absolute temperatures | |
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Conclusions | |
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Specific heat. The work-heat equivalent | |
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The heating curve | |
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Specific heat | |
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The mechanical equivalent of heat | |
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Conclusions | |
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Thermal equilibrium | |
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Equilibrium temperature | |
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Equilibrium between substances in different states | |
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Conclusions | |
