The paper proposes an important demonstration experiment that can be used at secondary schools in physics. The described experiment helps students learn the main concepts of the topic 'saturated vapor', namely, evaporation, condensation, dynamic equilibrium, saturation vapor, partial pressure, and the dependence of saturated vapor pressure on temperature.
The article proposes a new research object for a general physics course-the vapour Cartesian diver, designed to study the properties of saturated water vapour. Physics education puts great importance on the study of the saturated vapour state, as it is related to many fundamental laws and theories. For example, the temperature dependence of the saturated water vapour pressure allows the teacher to demonstrate the Le Chatelier's principle: increasing the temperature of a system in a dynamic equilibrium favours the endothermic change. That means that increasing the temperature increases the amount of vapour present, and so increases the saturated vapour pressure. The experimental setup proposed in this paper can be used as an example of an auto-oscillatory system, based on the properties of saturated vapour. The article describes a mathematical model of physical processes that occur in the experiment, and proposes a numerical solution method for the acquired system of equations. It shows that the results of numerical simulation coincide with the self-oscillation parameters from the real experiment. The proposed installation can also be considered as a model of a thermal engine.
The article describes research work that can help students observe and experimentally research the effects caused by the emission component of the filament current in fluorescent lamps’ cathodes. When analysing the work of electronic devices—multi-purpose lamps that use thermionic emission—research usually focuses on the current caused by the movement of electrons affected by the electric field between the cathode and the anode, and the cathode’s filament current is considered to be associated only with the movement of electrons through the metal conductor. However, the electric field’s potential drops along the cathode, which gives rise to the emission component of the filament current by the transfer of the emitted electrons along the cathode. The most convenient research object for this effect is a fluorescent lamp with a direct-filament cathode, where the emission component of the filament current manifests itself in the glow of the near-cathode space. The practical implications of the work lie in clarifying the algorithm for determining the lamp’s cathode temperature by its resistance.
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