The branch of physics that deals with the relationships between heat and other forms of energy. Four basic laws have been established. The first law is an example of the principle of conservation of energy. Thus, warm air outside can transfer its energy to a cold room, but transferring energy out of a cold room to the air outside requires extra energy as with an air conditioner. Since there can be no physical system with lower entropy, all entropy is thus defined to have a positive value.
Isobaric Process A process is said to be isobaric if the pressure of the system remains constant during each step of the process. The heat transferred to the system does work but also changes the internal energy of the system.
Isochoric or iso-volumetric Process A process is said to be Isochoric or iso-volumetric when the volume is held constant. In any Isochoric process, the work done by the system is always zero. For any two dimensional system, the heat energy transferred to that system is absorbed by it as its internal energy. The other name of this process is isometric process.
Example — When we heat any empty container, the air inside gains internal energy which can be felt due to increase in pressure and temperature. A given mass of water, however, can absorb nearly five times as much heat as an equal mass of aluminum. The specific heat of a gas is more complex and depends on whether it is measured at constant pressure or constant volume.
The unit for k is watts W per meter m per kelvin K. This property makes these materials useful for automobile radiators and cooling fins for computer chips because they can carry away heat quickly and exchange it with the environment.
Other materials are useful because they are extremely poor conductors of heat; this property is referred to as thermal resistance, or R -value, which describes the rate at which heat is transmitted through the material. These materials, such as rock wool, goose down and Styrofoam, are used for insulation in exterior building walls, winter coats and thermal coffee mugs. Newton's statement of the law translates from the original Latin as, "the excess of the degrees of the heat This results in an exponential decay in the temperature difference.
For example, if a warm object is placed in a cold bath, within a certain length of time, the difference in their temperatures will decrease by half. Then in that same length of time, the remaining difference will again decrease by half. This repeated halving of the temperature difference will continue at equal time intervals until it becomes too small to measure.
Heat can be transferred from one body to another or between a body and the environment by three different means: conduction, convection and radiation. Conduction is the transfer of energy through a solid material. Conduction between bodies occurs when they are in direct contact, and molecules transfer their energy across the interface. Convection is the transfer of heat to or from a fluid medium. Molecules in a gas or liquid in contact with a solid body transmit or absorb heat to or from that body and then move away, allowing other molecules to move into place and repeat the process.
Efficiency can be improved by increasing the surface area to be heated or cooled, as with a radiator, and by forcing the fluid to move over the surface, as with a fan.
Radiation is the emission of electromagnetic EM energy , particularly infrared photons that carry heat energy. All matter emits and absorbs some EM radiation, the net amount of which determines whether this causes a loss or gain in heat. The cycle exploits the relationships among pressure, volume and temperature of gasses and how an input of energy can change form and do work outside the system.
Compressing a gas increases its temperature so it becomes hotter than its environment. The definition for a thermodynamic process is the energy-infused transformation of a thermodynamic system whereby it moves from an introductory state to a final one.
An isobaric process. Takes place at a constant pressure. An isentropic process. Takes place at a constant entropy amount of environmental disorder. An isenthalpic process. Takes place at a constant enthalpy amount of internal heat. An adiabatic process. Takes place with a constant loss or gain of heat. Open Main Menu. Browse Courses My Classes. Sign In Subscribe Course Catalog. What is Thermodynamics? Because heat means energy in transit and dynamics is associated with movement; thermodynamics studies the movement of energy and how energy creates movement.
Thermodynamics and Heat: History. Eventually, in , J. Joule published the definitive paper which confirmed the idea that heat was a form of energy. After a series of experiments conducted by Joule, et. In thermodynamics, there are four laws. Broad based in their applications, they can be beneficial to all types of systems so long as the functioning element has to do with the balance of energy and transference of matter.
Far ranging examples of these applications include, at the turn of the 20 th century, Einstein 's theory on spontaneous emission as well as the current research that is being conducted on the thermodynamics of black holes.
The Zeroth Law of Thermodynamics.
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