用电功量热法测定水的比热容（Determination of specific heat of water by electric work calorimetry）.doc

用电功量热法测定水的比热容（Determination of specific heat of water by electric work calorimetry） Determination of specific heat of water by electric work calorimetry I. objective requirements 1. proficiency in calorimeter; 2. to measure the specific heat of water by means of electric calorimetry, so as to deepen the understanding of the first law of thermodynamics; 3. master a heat sink correction method - correct the final temperature. Two. Principle 1. determine the specific heat of water by electrothermal method In this experiment, the specific heat of water is measured by electric energy calorimetry, which is based on the Joule heating effect. If the voltage at the two ends of the heating wire is, and the current is passed, the electric field force does work in time: (19.1) All of this work is converted to heat, which increases the temperature of a water holding calorimeter system, which absorbs heat: (19.2) Which is the quality of water; the heat capacity of the calorimeter system (including the inner cylinder, the heating wire, the glass sleeve, the agitator, and the thermometer, the part of the submerged water, etc.). If there is no heat loss during energization, i.e.: (19.3) When both do not change with time, the integral of the formula (19.3) is made, and the temperature, time and temperature are the same: (19.4) If it is known, the specific heat of the effluent can be obtained by formula (19.4). Indeed, as in experiment 18, a series of specific heat capacity and a mass that are not easily weighed in the experiment can be calculated, but the theoretical calculations tend to deviate greatly from the actual process. This is because long time by shaking the stirrer will make it have more chances to contact with the external environment, and keep it away from the heat transfer to the external environment, may be several times on their own temperature to heat; heat the glass casing and a thermometer, also because the experimenter selected the amount of water. And the system