01 Thermodynamics

Pagina 1

L.D.D Advanced Building Physics - Thermodynamics 1 - PHYSICAL QUANTITIES AND MEASUREMENT Quality of an object ---> quasi-serial order (qualitative order)---> number assigned to the quasi-serial order ---> quantitative order
In the description of a physical phenomenon, only the terms that can be operationally defined must be used. These are called physical quantities. [Physics textbooks]
Each physical quantity is defined by the set of operations that are needed to obtain its measurement. Each entity that can not be operationally defined is an object that should not have a place within physical theories. [Percy Bridgman - manifesto of 'The logic of modern Physics']
The majority of physical quantities are defined by the set of operations (practical of theoretical) that are needed to obtain its measurement. [Moderate attitude - assumed in this course] --> Carnap: A theoretical term is significant if exists a statement s containing t such that from s and the remaining complex of the theory it's possible to derive an observational statement that couldn't be derived without s. (e.g. entropy ---> energy flows from higher to lower temperature) Quantitative description of reality --> measuring process - Choice of fundamental quantities - Choice of unit of measurement - Construction of samples of adopted units
We call 'measure of a quantity' the ratio n between the value of the quantity G and that of a quantity homogeneous to the one to be measured, UG, that we choose as measurement unit. To be adopted, a measurement unit has to meet the following requirements: - Precision - Accessibility - Reproducibility - Invariability (--> sth need to use atomic samples for this requirement) Note: - Accuracy: capability of an instrument to indicate the true value of measured quantity…