Template:Base quantities and count
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Base quantity Symbol for quantity Symbol for dimension Name of SI unit Symbol for SI unit [*] 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 amount of substance *,§ nX = NX·NA-1 N mole mol count *,$ NX X counting unit x unit entity *,$ UX U counting unit x charge *,€ QX = NX·zX·e I·T coulomb C = A·s luminous intensity Iv J candela cd
- [*] »SI base units, except for the canonical 'counting-unit' [x]. The following footnotes are canonical comments.
- * For the quantities n, N, U, and Q, the entity-type X of the unit-entity U has to be specified in the text and indicated by a subscript: nO2; Nce; QX.
- § Amount nX is a counting quantity, converting the counting-unit [x] into moles [mol] using the Avogadro constant, NA.
- $ Count NX equals the number of unit-entities UX. 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)). A unit-entity UX is not a count (UX is not a number of UX). NX has the dimension X of a count and UX has the dimension U of a unit entity, and both quantities have the same 'counting unit' [x].
- € Charge is a derived SI quantity, included here for comparison. Charge is a counting quantity, converting the counting unit [x] into coulombs [C] using the elementary charge, e, or converting moles [mol] into coulombs [C] using the Faraday constant, F. zX is the charge number of entity X, which is a constant for any defined entity X. QX = nX·zX·F