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  2. Conservation of energy - Wikipedia

    en.wikipedia.org/wiki/Conservation_of_energy

    This is an accepted version of this page This is the latest accepted revision, reviewed on 4 December 2024. Law of physics and chemistry This article is about the law of conservation of energy in physics. For sustainable energy resources, see Energy conservation. Part of a series on Continuum mechanics J = − D d φ d x {\displaystyle J=-D{\frac {d\varphi }{dx}}} Fick's laws of diffusion Laws ...

  3. First law of thermodynamics - Wikipedia

    en.wikipedia.org/wiki/First_law_of_thermodynamics

    The first law of thermodynamics for closed systems was originally induced from empirically observed evidence, including calorimetric evidence. It is nowadays, however, taken to provide the definition of heat via the law of conservation of energy and the definition of work in terms of changes in the external parameters of a system.

  4. Conserved current - Wikipedia

    en.wikipedia.org/wiki/Conserved_current

    The continuity equation for the conserved current is a statement of a conservation law. Examples of canonical conjugate quantities are: Time and energy - the continuous translational symmetry of time implies the conservation of energy; Space and momentum - the continuous translational symmetry of space implies the conservation of momentum

  5. Laws of thermodynamics - Wikipedia

    en.wikipedia.org/wiki/Laws_of_thermodynamics

    The first law of thermodynamics states that, when energy passes into or out of a system (as work, heat, or matter), the system's internal energy changes in accordance with the law of conservation of energy. The second law of thermodynamics states that in a natural thermodynamic process, the sum of the entropies of the interacting thermodynamic ...

  6. Continuity equation - Wikipedia

    en.wikipedia.org/wiki/Continuity_equation

    In electromagnetic theory, the continuity equation is an empirical law expressing (local) charge conservation. Mathematically it is an automatic consequence of Maxwell's equations, although charge conservation is more fundamental than Maxwell's equations.

  7. Conservation law - Wikipedia

    en.wikipedia.org/wiki/Conservation_law

    A local conservation law is usually expressed mathematically as a continuity equation, a partial differential equation which gives a relation between the amount of the quantity and the "transport" of that quantity. It states that the amount of the conserved quantity at a point or within a volume can only change by the amount of the quantity ...

  8. Charge conservation - Wikipedia

    en.wikipedia.org/wiki/Charge_conservation

    Mathematically, we can state the law of charge conservation as a continuity equation: = ˙ ˙ (). where / is the electric charge accumulation rate in a specific volume at time t, ˙ is the amount of charge flowing into the volume and ˙ is the amount of charge flowing out of the volume; both amounts are regarded as generic functions of time.

  9. Poynting's theorem - Wikipedia

    en.wikipedia.org/wiki/Poynting's_theorem

    In electrodynamics, Poynting's theorem is a statement of conservation of energy for electromagnetic fields developed by British physicist John Henry Poynting. [1] It states that in a given volume, the stored energy changes at a rate given by the work done on the charges within the volume, minus the rate at which energy leaves the volume.