Example Weatherglass

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The weather glass provides a context for didactically valuable experimentation and discussion. There are many reasons for this. It provides a rich context for elaboration of the ideal gas law, in a way that makes the formulae and diagrams more meaningful for basic physics courses. It has survived more than a millennium and it is still commercially available. It was used by the Arab people well before they came to Spain in the 8th century. Hence, it allows for historical links across many centuries. It can trigger interest and motivation in teachers and students because of the widespread attention to weather forecasting and climate change. It is an emblematic experiment of the low-cost laboratory approach, which can be constructed readily with everyday, easily obtained materials. It is appropriate for classroom exercise and homework, a collaborative student activity or a project in a teacher preparation program. Experimenting with a weather glass and discussing the underlying physics concepts and laws gives opportunities to overcome some difficulties that learners may encounter in understanding both the role and meaning of the ideal gas law and hydrostatic pressure in a liquid. In particular, this experiment is an opportunity to discuss the relevance of two quantities: external pressure and temperature, and thereafter the difficulty to formulate conclusions in case one of these quantities is not kept constant. This paper also discusses some approximations, based on specific measurements of this apparatus, The approximations are useful in exploring the influence of the pressure difference on the level difference between the liquid in the vessel and in the tube (body and spout of the weather glass). Our analysis also addresses errors in measurements and their consequences.

Title	Author	Type	Modified
Weatherglass	Christian Ucke	File	2011-01-28 19:01