{"id":16435,"date":"2018-01-09T16:40:58","date_gmt":"2018-01-09T16:40:58","guid":{"rendered":"http:\/\/sitepourvtc.com\/?page_id=16435"},"modified":"2022-11-05T12:04:29","modified_gmt":"2022-11-05T12:04:29","slug":"what-is-temperature-physics","status":"publish","type":"page","link":"https:\/\/sitepourvtc.com\/nuclear-engineering\/thermodynamics\/thermodynamic-properties\/what-is-temperature-physics\/","title":{"rendered":"What is Temperature – Physics"},"content":{"rendered":"
In physics<\/strong> and everyday life,<\/strong> a temperature<\/strong> is an objective comparative measurement of hot or cold<\/strong> based on our sense of touch. \u00a0A body that usually feels hot has a higher temperature than a similar body that feels cold. But this definition is not a simple matter. For example, a metal rod feels colder than a plastic rod at room temperature simply because metals are generally better at conducting heat away from the skin, as are plastics.<\/div><\/div>\n

Simply hotness<\/strong> may be represented abstractly,<\/strong> and therefore it is necessary to have an objective way of measuring temperature. It is one of the basic thermodynamic properties.<\/p>\n

Thermal Equilibrium<\/h2>\n
\"Zeroth<\/a>
Zeroth law of thermodynamics: If two systems are both in thermal equilibrium with a third, then they are in thermal equilibrium with each other.<\/figcaption><\/figure>\n

A particularly important concept is thermodynamic equilibrium<\/strong>. In general, when two objects are brought into thermal contact<\/strong>, heat will flow<\/strong> between them until<\/strong> they come into equilibrium<\/strong> with each other. \u00a0When a temperature difference<\/strong> does exist, heat flows spontaneously from the warmer system to the colder system<\/strong>. Heat transfer occurs by conduction<\/strong> or by thermal radiation<\/strong>. When the flow of heat stops<\/strong>, they are said to be at the same temperature<\/strong>. They are then said to be in thermal equilibrium<\/strong>.<\/p>\n

For example, you leave a thermometer<\/strong> in a cup of coffee. As the two objects interact, the thermometer becomes hotter, and the coffee cools off a little until they come into thermal equilibrium<\/strong>. Two objects are defined to be in thermal equilibrium if, when placed in thermal contact, no net energy flows<\/strong> from one to the other, and their temperatures don\u2019t change<\/strong>. We may postulate:<\/p>\n

When the two objects are in thermal equilibrium, their temperatures are equal. <\/em><\/strong><\/p>\n

This is a subject of a law that is called the \u201czeroth law of thermodynamics\u201d.<\/p>\n

<\/span>Zeroth Law of Thermodynamics<\/div>
\n
\"Zeroth<\/a>
Zeroth law of thermodynamics: If two systems are both in thermal equilibrium with a third, then they are in thermal equilibrium with each other.<\/figcaption><\/figure>\n

We can discover an important property of thermal equilibrium<\/strong> by considering three systems<\/strong>. A, B, and C are initially\u00a0not in thermal equilibrium<\/strong>. We separate systems A and B with an adiabatic wall (ideal insulating material), but we let system C interact with systems A and B. We wait until thermal equilibrium<\/strong> is reached; then, A and B are in thermal equilibrium with C. But are they in thermal equilibrium with each other?<\/p>\n

According to many experiments<\/strong>, there will be no net energy flow<\/strong> between A<\/strong> and B<\/strong>. This is experimental evidence<\/strong> of the following statement:<\/p>\n

If two systems are both in thermal equilibrium with a third, then they are in thermal equilibrium with each other. \u00a0<\/em><\/strong><\/p>\n

This statement is known as the zeroth law of thermodynamics<\/strong>. It has this unusual name because it was not until after the great first and second laws of thermodynamics were worked out that scientists realized that this obvious postulate needed to be stated first.<\/p>\n

This law provides a definition<\/strong> and method<\/strong> of defining temperatures<\/strong>, perhaps the most important intensive property<\/a><\/strong> of a system when dealing with thermal energy conversion problems. Temperature is a system property that determines whether the system will be in thermal equilibrium with other systems. When two systems are in thermal equilibrium, their temperatures are, by definition, equal, and no net thermal energy will be exchanged between them. Thus the importance of the zeroth law is that it allows a useful definition of temperature.<\/div><\/div><\/div>

<\/div>Temperature<\/strong> is a very important characteristics of matter. Many properties<\/strong> of matter change with temperature<\/strong>. The length of a metal rod, steam pressure<\/a> in a boiler, the ability of a wire to conduct an electric current, and the color of a very hot glowing object. All these depend on temperature<\/strong>.<\/p>\n

For example, most materials expand when their temperature is increased. This property is very important in all of science and engineering, even in nuclear engineering<\/a>. The thermodynamic efficiency<\/strong> of power plants changes with inlet steam temperature or even with the outside temperature. At higher temperatures, solids such as steel glow orange or even white, depending on temperature. The white light from an ordinary incandescent lightbulb comes from an extremely hot tungsten wire. It can be seen temperature is one of the fundamental characteristics that describe matter and influences matter behavior.<\/p>\n

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Kinetic Temperature<\/h2>\n

The kinetic theory<\/strong>\u00a0of gases provides a microscopic explanation of temperature. It is based on the fact that during an elastic collision<\/a> between a molecule with high kinetic energy and one with low kinetic energy, part of the energy will transfer to the molecule of lower kinetic energy. Temperature<\/strong> is therefore related to the kinetic energies<\/strong> of the molecules of a material. Since this relationship is fairly complex, it will be discussed later.[\/su_spoiler][\/su_accordion]\n

Temperature Scales<\/h2>\n

\"Temperature<\/a>When using a thermometer, we need to mark a scale on the tube wall with numbers. We have to define a temperature scale<\/strong>. A temperature scale<\/em><\/strong> is a way to measure temperature relative to a starting point<\/strong> (0 or zero) and a unit of measurement<\/strong>.<\/p>\n

These numbers are arbitrary, and historically many different schemes have been used. For example, this was done by defining some physical occurrences at given temperatures\u2014such as the freezing<\/strong> and boiling points of water<\/a>\u00a0<\/strong>\u2014 and defining them as 0 and 100, respectively.<\/p>\n

Some several scales and units exist for measuring temperature. The most common are:<\/p>\n