In physics, heating is transfer of energy, from a hotter body to a colder one, other than by work or transfer of matter. It occurs spontaneously whenever a suitable physical pathway exists between the bodies.[1][2][3][4][5][6] The pathway can be direct, as in conduction and radiation, or indirect, as in convective circulation.[7][8][9] Heating is a dissipative process. Heat is not a state function of a system. Kinetic theory explains transfers of energy as heat as macroscopic manifestations of the motions and interactions of microscopic constituents such as molecules and photons. The quantity of energy transferred as heat is a scalar expressed in an energy unit such as the joule (J) (SI), with a sign that is customarily positive when a transfer adds to the energy of a system. It can be measured by calorimetry,[10] or determined by calculations based on other quantities, relying on the first law of thermodynamics. In calorimetry, latent heat changes a systems state without temperature change, while sensible heat changes its temperature, leaving some other state variable(s) unchanged; the terms latent and sensible are correlative. (c)
Posted on: Wed, 08 Oct 2014 06:12:03 +0000
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