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Quantity
Description
A quantity is the attribute of a phenomenon, body or substance that may be distinguished qualitatively and determined quantitatively. A dimensional quantity is a number (variable, parameter, or constant) connected to its dimension, which is different from 1. {Quote} The value of a quantity is generally expressed as the product of a number and a unit. The unit is simply a particular example of the quantity concerned which is used as a reference, and the number is the ratio of the value of the quantity to the unit. {end of quote: Bureau International des Poids et Mesures 2019 The International System of Units (SI), p. 127)}.
Abbreviation: Q
Reference: Gnaiger MitoFit Preprint Arch 2020.4
Base quantities and count
Quantity Symbol for quantity Q Symbol for dimension Name of abstract unit u_{Q} Symbol for unit u_{Q} [*] elementary entity ^{*,$} U_{X} U elementary unit x count ^{*,$} N_{X} = N·U_{X} X elementary unit x amount of substance ^{*,§} n_{X} = N_{X}·N_{A}^{-1} N mole mol charge ^{*,€} Q_{el} = z_{X}·e·N_{X} I·T coulomb C = A·s length l L meter m mass m M kilogram kg time t T second s electric current I I ampere A thermodynamic temperature T Θ kelvin K luminous intensity I_{v} J candela cd
- [*] SI units, except for the canonical 'elementary unit' [x]. The following footnotes are canonical comments.
- ^{*} For the elementary quantities N_{X}, n_{X}, and Q_{el}, the entity-type X of the elementary entity U_{X} has to be specified in the text and indicated by a subscript: n_{O2}; N_{ce}; Q_{el}.
- ^{$} Count N_{X} equals the number of elementary entities U_{X}. In the SI, the quantity 'count' is explicitly considered as an exception: "Each of the seven base quantities used in the SI is regarded as having its own dimension. .. All other quantities, with the exception of counts, are derived quantities" (Bureau International des Poids et Mesures 2019 The International System of Units (SI)). An elementary entity U_{X} is a material unit, it is not a count (U_{X} is not a number of U_{X}). N_{X} has the dimension X of a count and U_{X} has the dimension U of an elementary entity; both quantities have the same abstract unit, the 'elementary unit' [x].
- ^{§} Amount n_{X} is an elementary quantity, converting the elementary unit [x] into the SI base unit mole [mol] using the Avogadro constant N_{A}.
- ^{€} Charge is a derived SI quantity. Charge is an elementary quantity, converting the elementary unit [x] into coulombs [C] using the elementary charge e, or converting moles [mol] into coulombs [C] using the Faraday constant F. z_{X} is the charge number per elementary entity U_{X}, which is a constant for any defined elementary entity U_{X}. Q_{el} = z_{X}·F·n_{X}
Quantities and units
- 1.1. Quantity: "property of a phenomenon, body, or substance, where the property has a magnitude that can be expressed as a number and a reference. .. The generic concept ‘quantity’ can be divided into several levels of specific concepts". The generic concept 'length' can be divided into radius of a circle or wavelength. "A reference can be a measurement unit, a measurement procedure, a reference material, or a combination of such. .. The symbols for quantities are written in italics. .. The concept ‘quantity’ may be generically divided into, e.g. ‘physical quantity’, ‘chemical quantity’, and ‘biological quantity’, or base quantity and derived quantity."
- 1.2. Kind of quantity: "aspect common to mutually comparable quantities. .. The quantities diameter, circumference, and wavelength are generally considered to be quantities of the same kind, namely of the kind of quantity called length.
- 1.7. Quantity dimension; dimension of a quantity: "expression of the dependence of a quantity on the base quantities of a system of quantities as a product of powers of factors corresponding to the base quantities, omitting any numerical factor."
- 1.19. Quantity value; value of a quantity: "number and reference together expressing magnitude of a quantity"
References
Bioblast link | Reference | Year |
---|---|---|
Bureau International des Poids et Mesures 2019 The International System of Units (SI) | Bureau International des Poids et Mesures (2019) The International System of Units (SI). 9th edition:117-216 ISBN 978-92-822-2272-0. | 2019 |
Gnaiger MitoFit Preprint Arch 2020.4 | Gnaiger Erich (2020) Canonical reviewer's comments on: Bureau International des Poids et Mesures (2019) The International System of Units (SI) 9th ed. MitoFit Preprint Arch 2020.4 doi:10.26124/mitofit:200004. | 2020 |
MitoPedia concepts: MitoFit Quality Control System, Ergodynamics