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  2. Relative change - Wikipedia

    en.wikipedia.org/wiki/Relative_change

    The actual difference is not usually a good way to compare the numbers, in particular because it depends on the unit of measurement. For instance, 1 m is the same as 100 cm, but the absolute difference between 2 and 1 m is 1 while the absolute difference between 200 and 100 cm is 100, giving the impression of a larger difference. [4]

  3. Coefficient of performance - Wikipedia

    en.wikipedia.org/wiki/Coefficient_of_performance

    Measured values for actual systems will always be significantly less than these theoretical maxima. In Europe, the standard test conditions for ground source heat pump units use 308 K (35 °C; 95 °F) for and 273 K (0 °C; 32 °F) for . According to the above formula, the maximum theoretical COPs would be

  4. Energy conversion efficiency - Wikipedia

    en.wikipedia.org/wiki/Energy_conversion_efficiency

    The theoretical-maximum efficacy lowers for wavelengths at either side of 555 nm. For example, low-pressure sodium lamps produce monochromatic light at 589 nm with a luminous efficacy of 200 lm/w, which is the highest of any lamp. The theoretical-maximum efficacy at that wavelength is 525 lm/w, so the lamp has a luminous efficiency of 38.1%.

  5. Thermal efficiency - Wikipedia

    en.wikipedia.org/wiki/Thermal_efficiency

    The above efficiency formulas are based on simple idealized mathematical models of engines, with no friction and working fluids that obey simplified thermodynamic models. Real engines have many departures from ideal behavior that waste energy, reducing actual efficiencies below the theoretical values given above. Examples are: friction of ...

  6. Theoretical physics - Wikipedia

    en.wikipedia.org/wiki/Theoretical_physics

    Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and systems to rationalize, explain, and predict natural phenomena. This is in contrast to experimental physics , which uses experimental tools to probe these phenomena.

  7. Mathematical model - Wikipedia

    en.wikipedia.org/wiki/Mathematical_model

    Linear vs. nonlinear. If all the operators in a mathematical model exhibit linearity, the resulting mathematical model is defined as linear. A model is considered to be nonlinear otherwise. The definition of linearity and nonlinearity is dependent on context, and linear models may have nonlinear expressions in them.

  8. Analytical mechanics - Wikipedia

    en.wikipedia.org/wiki/Analytical_mechanics

    In theoretical physics and mathematical physics, analytical mechanics, or theoretical mechanics is a collection of closely related formulations of classical mechanics. Analytical mechanics uses scalar properties of motion representing the system as a whole—usually its kinetic energy and potential energy .

  9. Action (physics) - Wikipedia

    en.wikipedia.org/wiki/Action_(physics)

    The action is defined by an integral, and the classical equations of motion of a system can be derived by minimizing the value of that integral. The action principle provides deep insights into physics, and is an important concept in modern theoretical physics. Various action principles and related concepts are summarized below.