When learning about new physical processes, our goal is to reach a certain level of process mechanism knowledge, which enables us to make result predictions of the physical process in question. In most processes that are dealt with at the primary school physics level, the physical quantities are considered uniquely and unambiguously, where the predictions of the forthcoming state are much easier. This means that regardless of the knowledge and recognition of the previous state of the system, the future quantity values can be predicted with great certainty. In certain cases the system behaves in a way, where with a single quantity value two different values of the dependable quantity are possible. An example of such connection is hysteresis. When treating the systems with hysteresis the prediction without knowledge of previous or inner states results impossible. Hysteresis is defined as a physical phenomenon where a certain quantity depends on a momentary value and the previous value of another quantity.
Such links can be detected in the fields like biology, chemistry, economics, psychology, etc. The hysteresis in physics is researched to great extent in electromagnetism, it can also be observed in many physical areas, such as phase transitions.
The case of sodium acetate, which serves as the filling in heating bags shows that the prediction of the state with a defined temperature proves typically infeasible without prior knowledge of the history of the state. With certain temperature it can occur in a solid or liquid form.
The observation of hysteresis from the case above is suitable for experimental work in primary school classes.
The thesis deals with phenomena where hysteresis can be observed, namely with magnetisation of the core in the coil, water sub-cooling, temperature of phase transitions with the gelling agent agar, elastic stretching, differences connected to the base regarding the location of the moving vehicle, display of the corresponding gear in the gear box while driving a car, and with triggering the phase change with sodium acetate in a heating bag.
The above experiments are described in this thesis and their physical background is presented. The experiments are evaluated and assessed according to their suitability for primary school presentations.
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