Entropy is a scientific concept as well as a measurable physical property that is most commonly associated with a state of disorder, randomness, or uncertainty. The term and the concept are used in diverse fields, from classical thermodynamics, where it was first recognized, to the microscopic description of nature in statistical physics, and to the principles of information theory. It has found far-ranging applications in chemistry and physics, in biological systems and their relation to life, in cosmology, economics, sociology, weather science, climate change, and information systems including the transmission of information in telecommunication.
In thermodynamics and engineering, a heat engine is a system that converts heat to mechanical energy, which can then be used to do mechanical work. It does this by bringing a working substance from a higher state temperature to a lower state temperature. A heat source generates thermal energy that brings the working substance to the higher temperature state. The working substance generates work in the working body of the engine while transferring heat to the colder sink until it reaches a lower temperature state. During this process some of the thermal energy is converted into work by exploiting the properties of the working substance. The working substance can be any system with a non-zero heat capacity, but it usually is a gas or liquid. During this process, some heat is normally lost to the surroundings and is not converted to work. Also, some energy is unusable because of friction and drag.
The process by which heat is transferred from the hotter end to the colder end of object is known as conduction.
The second law of thermodynamics is a physical law of thermodynamics about heat and loss in its conversion. It can be stated in various ways, the simplest being:
Not all heat energy can be converted into work in a cyclic process.
Heat capacity or thermal capacity is a physical property of matter, defined as the amount of heat to be supplied to an object to produce a unit change in its temperature. The SI unit of heat capacity is joule per kelvin (J/K).
Carnot's theorem, developed in 1824 by Nicolas Léonard Sadi Carnot, also called Carnot's rule, is a principle that specifies limits on the maximum efficiency that any heat engine can obtain.
The coefficient of performance or COP of a heat pump, refrigerator or air conditioning system is a ratio of useful heating or cooling provided to work (energy) required. Higher COPs equate to higher efficiency, lower energy (power) consumption and thus lower operating costs. The COP usually exceeds 1, especially in heat pumps, because, instead of just converting work to heat, it pumps additional heat from a heat source to where the heat is required. Most air conditioners have a COP of 2.3 to 3.5. Less work is required to move heat than for conversion into heat, and because of this, heat pumps, air conditioners and refrigeration systems can have a coefficient of performance greater than one. However, this does not mean that they are more than 100% efficient, in other words, no heat engine can have a thermal efficiency of 100% or greater. For complete systems, COP calculations should include energy consumption of all power consuming auxiliaries. The COP is highly dependent on operating conditions, especially absolute temperature and relative temperature between sink and system, and is often graphed or averaged against expected conditions. Performance of absorption refrigerator chillers is typically much lower, as they are not heat pumps relying on compression, but instead rely on chemical reactions driven by heat.
In motorsports, the pole position is the position at the front at the start of a racing event. This position may be inside or outside of the front row, depending on where the racing line is on the particular circuit, but it will always be ahead of the other vehicle(s) on the front row. This position is typically given to the vehicle and driver with the best qualifying time in the trials before the race. This number-one qualifying driver is referred to as the pole-sitter.
Thermodynamic heat pump cycles or refrigeration cycles are the conceptual and mathematical models for heat pump, air conditioning and refrigeration systems. A heat pump is a mechanical system that allows for the transmission of heat from one location at a lower temperature to another location at a higher temperature. Thus a heat pump may be thought of as a "heater" if the objective is to warm the heat sink, or a "refrigerator" or “cooler” if the objective is to cool the heat source. In either case, the operating principles are similar. Heat is moved from a cold place to a warm place.
In thermodynamics, heat is energy in transfer to or from a thermodynamic system, by mechanisms other than thermodynamic work or transfer of matter.
Temperature is a physical quantity that expresses hot and cold or a measure of the average kinetic energy of the atoms or molecules in the system. It is the manifestation of thermal energy, present in all matter, which is the source of the occurrence of heat, the flow of energy from a hotter body in contact with a colder body.
At the 8th National Games of the People's Republic of China, the athletics events were held in Shanghai in October 1997.
The men's 100 metres event at the 2013 Summer Universiade was held on 7–8 July.
The men's 100 metres at the 2013 Asian Athletics Championships was held at the Shree Shiv Chhatrapati Sports Complex on 3 and 4 July.
The men's 100 metres at the 2013 World Championships in Athletics was held at the Luzhniki Stadium on 10 and 11 August.
The men's 200 metres at the 2013 World Championships in Athletics was held at the Luzhniki Stadium on 16 and 17 August.
The men's 110 metres hurdles at the 2013 World Championships in Athletics was held at the Luzhniki Stadium on 11 and 12 August.
The women's 100 metres hurdles at the 2013 World Championships in Athletics was held at the Luzhniki Stadium on 12–15 August.
The women's 100 metres at the 2013 World Championships in Athletics was held at the Luzhniki Stadium on 11–12 August and was won by Shelly-Ann Fraser-Pryce.
The women's 200 metres at the 2013 World Championships in Athletics was held at the Luzhniki Stadium on 15–16 August.
