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The distance of the light below the suspension point is equal to (8 tan 10°) m = 1.4 m (to two significant figures). $\displaystyle T= \lim_\,N = 5.8\times10^2\,N$ (to two significant figures) (ii) The ideal–gas absolute scale of temperature is defined by the relationship A thermometer can be calibrated by noting the value of some thermometric property at these fixed points and assuming that a change in temperature of 1° corresponds to 1/100 of the change in the thermometric property between the two points. (a) (i) Centigrade scales define the freezing and boiling points of water at a pressure of 1 atm as 0° and 100°, respectively. However, if you have difficulty with more than two of the Exit questions you are strongly advised to study the whole module. If you have difficulty with only one or two of the questions you should follow the guidance given in the answers and read the relevant parts of the module. If you are sure that you can meet each of these achievements, try the Subsection 5.3Exit test. Study comment Can you answer the following Fast track questions? If you answer the questions successfully you need only glance through the module before looking at the Subsection 5.1Module summary and the Subsection 5.2Achievements. If not, proceed directly to the Subsection 1.3Ready to study? section. If so, try the following Fast track questions. Study comment Having read the introduction you may feel that you are already familiar with the material covered by this module and that you do not need to study it. This section also touches briefly on the idea of a more fundamental scale of temperature based on thermodynamic principles and describes recent recommendations for the practical definition of temperature scales.
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In Section 4 both themes are brought together to show how knowledge of the properties of an ideal gas leads to an absolute scale of temperature and to an accurate method of temperature measurement. Section 3 deals with the properties of ideal gases and introduces Boyle’s law, Charles’ law, the ideal gas law and the equation of state of an ideal gas. Some basic ideas about temperature and its measurement are discussed in Section 2. At first glance these properties might seem unrelated to temperature but as you will see they are all intimately bound together, partly because an understanding of these properties requires an understanding of temperature and partly because monitoring such properties turns out to be an excellent method of measuring temperature. Examples of the macroscopic properties of a gas might be its volume, pressure or density. We will use the term macroscopic in this context to mean ‘on a scale sufficiently large that we do not need to worry about the behaviour of atoms or molecules’. The module is also concerned with the macroscopic or bulk properties of gases. In doing so we hope to provide a clear idea of its scientific meaning. What is ‘hotness’ after all? This module will examine the idea of temperature and its measurement. Most school texts describe temperature as ‘degree of hotness’ – but that is somewhat unsatisfactory. We all have an intuitive idea of what it means, yet it is a very elusive concept to try and pin down more precisely. Temperature is a word we probably hear every day of our lives: ‘The temperature must be in the nineties’ ‘Bake the cake at a temperature of 200 ☌’ etc.