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  2. Heat transfer physics - Wikipedia

    en.wikipedia.org/wiki/Heat_transfer_physics

    The macroscopic energy equation for infinitesimal volume used in heat transfer analysis is [6] = +, ˙, where q is heat flux vector, −ρc p (∂T/∂t) is temporal change of internal energy (ρ is density, c p is specific heat capacity at constant pressure, T is temperature and t is time), and ˙ is the energy conversion to and from thermal ...

  3. Thermodynamic system - Wikipedia

    en.wikipedia.org/wiki/Thermodynamic_system

    The system is delimited by walls or boundaries, either actual or notional, across which conserved (such as matter and energy) or unconserved (such as entropy) quantities can pass into and out of the system. The space outside the thermodynamic system is known as the surroundings, a reservoir, or the environment. The properties of the walls ...

  4. First law of thermodynamics - Wikipedia

    en.wikipedia.org/wiki/First_law_of_thermodynamics

    In general, matter in diffusive motion carries with it some internal energy, and some microscopic potential energy changes accompany the motion. An open system is not adiabatically enclosed. There are some cases in which a process for an open system can, for particular purposes, be considered as if it were for a closed system.

  5. Interstellar medium - Wikipedia

    en.wikipedia.org/wiki/Interstellar_medium

    This process yields 4.48 eV of energy distributed over the rotational and vibrational modes, kinetic energy of the H 2 molecule, as well as heating the dust grain. This kinetic energy, as well as the energy transferred from de-excitation of the hydrogen molecule through collisions, heats the gas.

  6. Cosmological phase transition - Wikipedia

    en.wikipedia.org/wiki/Cosmological_phase_transition

    A cosmological phase transition is an overall change in the state of matter across the whole universe. The success of the Big Bang model led researchers to conjecture possible cosmological phase transitions taking place in the very early universe, at a time when it was much hotter and denser than today.

  7. Vacuum energy - Wikipedia

    en.wikipedia.org/wiki/Vacuum_energy

    Vacuum energy has a number of consequences. In 1948, Dutch physicists Hendrik B. G. Casimir and Dirk Polder predicted the existence of a tiny attractive force between closely placed metal plates due to resonances in the vacuum energy in the space between them. This is now known as the Casimir effect and has since been extensively experimentally ...

  8. Energy–momentum relation - Wikipedia

    en.wikipedia.org/wiki/Energy–momentum_relation

    The energy and momentum of an object measured in two inertial frames in energy–momentum space – the yellow frame measures E and p while the blue frame measures E ′ and p ′. The green arrow is the four-momentum P of an object with length proportional to its rest mass m 0.

  9. Second law of thermodynamics - Wikipedia

    en.wikipedia.org/wiki/Second_law_of_thermodynamics

    The energy and entropy of unpolarized blackbody thermal radiation, is calculated using the spectral energy and entropy radiance expressions derived by Max Planck [63] using equilibrium statistical mechanics, = ⁡ (), = ((+) ⁡ (+) ⁡ ()) where c is the speed of light, k is the Boltzmann constant, h is the Planck constant, ν is frequency ...