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  2. Atomic units - Wikipedia

    en.wikipedia.org/wiki/Atomic_units

    A set of base units in the atomic system as in one proposal are the electron rest mass, the magnitude of the electronic charge, the Planck constant, and the permittivity. [6] [9] In the atomic units system, each of these takes the value 1; the corresponding values in the International System of Units [10]: 132 are given in the table.

  3. Natural units - Wikipedia

    en.wikipedia.org/wiki/Natural_units

    In physics, natural unit systems are measurement systems for which selected physical constants have been set to 1 through nondimensionalization of physical units.For example, the speed of light c may be set to 1, and it may then be omitted, equating mass and energy directly E = m rather than using c as a conversion factor in the typical mass–energy equivalence equation E = mc 2.

  4. International System of Units - Wikipedia

    en.wikipedia.org/wiki/International_System_of_Units

    The systems formalised the concept of a collection of related units called a coherent system of units. In a coherent system, base units combine to define derived units without extra factors. [4]: 2 For example, using metre per second is coherent in a system that uses metre for length and second for time, but kilometre per hour is not coherent.

  5. System of units of measurement - Wikipedia

    en.wikipedia.org/wiki/System_of_units_of_measurement

    Planck units is system of geometrized units in which the reduced Planck constant is included in the list of defining constants. It is based on only properties of free space rather than of any object or particle. Stoney units is a system of geometrized units in which the Coulomb constant and the elementary charge are included.

  6. Quantities, Units and Symbols in Physical Chemistry

    en.wikipedia.org/wiki/Quantities,_Units_and...

    Quantities, Units and Symbols in Physical Chemistry, also known as the Green Book, is a compilation of terms and symbols widely used in the field of physical chemistry. It also includes a table of physical constants , tables listing the properties of elementary particles , chemical elements , and nuclides , and information about conversion ...

  7. Historical definitions of the SI base units - Wikipedia

    en.wikipedia.org/wiki/Historical_definitions_of...

    The Celsius scale: the Kelvin scale uses the degree Celsius for its unit increment, but is a thermodynamic scale (0 K is absolute zero). Θ mole: mol amount of substance "1. The mole is the amount of substance of a system which contains as many elementary entities as there are atoms in 0.012 kilogram of carbon 12; its symbol is 'mol'. 2.

  8. Base unit of measurement - Wikipedia

    en.wikipedia.org/wiki/Base_unit_of_measurement

    A base unit of measurement (also referred to as a base unit or fundamental unit) is a unit of measurement adopted for a base quantity. A base quantity is one of a conventionally chosen subset of physical quantities , where no quantity in the subset can be expressed in terms of the others.

  9. Systems theory - Wikipedia

    en.wikipedia.org/wiki/Systems_theory

    Systems theory is the transdisciplinary [1] study of systems, i.e. cohesive groups of interrelated, interdependent components that can be natural or artificial.Every system has causal boundaries, is influenced by its context, defined by its structure, function and role, and expressed through its relations with other systems.