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m/s 5: L T −5: vector Current density: J →: Electric current per unit cross-section area A/m 2: L −2 I: conserved, intensive, vector Electric dipole moment: p: Measure of the separation of equal and opposite electric charges C⋅m L T I: vector Electric displacement field: D →: Strength of the electric displacement C/m 2: L −2 T I ...
In engineering and science, dimensional analysis is the analysis of the relationships between different physical quantities by identifying their base quantities (such as length, mass, time, and electric current) and units of measurement (such as metres and grams) and tracking these dimensions as calculations or comparisons are performed.
There are seven ISQ base quantities. The symbols for them, as for other quantities, are written in italics. [1] The dimension of a physical quantity does not include magnitude or units. The conventional symbolic representation of the dimension of a base quantity is a single upper-case letter in roman (upright) sans-serif [c] type.
The derived units in the SI are formed by powers, products, or quotients of the base units and are unlimited in number. [5]: 103 [4]: 14, 16 Arrangement of the principal measurements in physics based on the mathematical manipulation of length, time, and mass
The SI has special names for 22 of these coherent derived units (for example, hertz, the SI unit of measurement of frequency), but the rest merely reflect their derivation: for example, the square metre (m 2), the SI derived unit of area; and the kilogram per cubic metre (kg/m 3 or kg⋅m −3), the SI derived unit of density.
Historical SI base units Name Symbol Measure Pre-2019 (2005) formal definition [2] Historical origin / justification Dimension symbol; metre: m length "The metre is the length of the path travelled by light in vacuum during a time interval of 1 / 299 792 458 of a second." 17th CGPM (1983, Resolution 1, CR, 97)
Usually dimension tables do not reference other dimensions via foreign keys. When this happens, the referenced dimension is called an outrigger dimension. Outrigger dimensions should be considered a data warehouse anti-pattern: it is considered a better practice to use some fact tables that relate the two dimensions. [9]
Some physicists have not recognized temperature as a base dimension since it simply expresses the energy per particle per degree of freedom which can be expressed in terms of energy (or mass, length, and time). [4] Duff argues that only dimensionless values have physical meaning and all dimensional units are human constructs. [5]