Base quantities




Base quantities are those quantities which are distinct in nature and in some cases have historically not been defined in terms of other quantities. Base quantities are those quantities on the basis of which other quantities can be expressed. The seven base quantities of the International System of Quantities (ISQ) and their corresponding SI units and dimensions are listed in the following table. Other conventions may have a different number of base units (e.g. the CGS and MKS systems of units).

International System of Quantities base quantities
Quantity SI unit Dimension
symbol
Name(s) (Common) symbol(s) Name Symbol
Length, width, height, depth, distance a, b, c, d, h, l, r, s, w, x, y, z metre m L
Time t, τ second s T
Mass m kilogram kg M
Absolute temperature T, θ kelvin K Θ
Amount of substance n mole mol N
Electric current i, I ampere A I
Luminous intensity Iv candela cd J
Plane angle α, β, γ, θ, φ, χ radian rad None
Solid angle ω, Ω steradian sr None

The last two angular units, plane angle and solid angle, are subsidiary units used in the SI, but are treated as dimensionless. The subsidiary units are used for convenience to differentiate between a truly dimensionless quantity (pure number) and an angle, which are different measurements.

Comments

Post a Comment

Popular posts from this blog

19)Revealed: What to expect on Republic Morning 2021and what not to

India Republic Day -- Republic Day 2021: In 2020it was the agitation up against the Citizenship Amendment Act (CAA). Nowthousands of farmerstypically from Punjab and Haryanahave been camping at the edges of Delhi for more than a couple of monthsdemanding the Centre repeal the three farm laws. For any second year in a rowRepublic Day celebrations inside the national capital will be kept under the shadow of strong protests against laws handed by the Centre. In 2020it was the agitation up against the Citizenship Amendment Act (CAA). This timethousands of farmerstypically from Punjab and Haryanahave been camping at the edges of Delhi for more than a couple of monthsdemanding the Centre repeal the three farm laws. This specific years Republic Day attend will also be the first major community event in pandemic times. What is new this year The case will be pared down the number of spectatorsthe size of walking contingents and other side points of interest. The spectator size have been redu...
Read more

Numbers and elementary functions

Numerical quantities, even those denoted by letters, are usually printed in roman (upright) type, though sometimes in italic. Symbols for elementary functions (circular trigonometric, hyperbolic, logarithmic etc.), changes in a quantity like Δ in Δ y or operators like d in d x , are also recommended to be printed in roman type. Examples: Real numbers, such as 1 or √ 2 , e, the base of natural logarithms, i, the imaginary unit, π for the ratio of a circle's circumference to its diameter, 3.14159265358979323846264338327950288... δ x , Δ y , d z , representing differences (finite or otherwise) in the quantities x , y and z sin α , sinh γ , log x
Read more

Subscripts and indices

Subscripts are used for two reasons, to simply attach a name to the quantity or associate it with another quantity, or represent a specific vector, matrix, or tensor component. clarification needed Name reference: The quantity has a subscripted or superscripted single letter, group of letters, or complete word, to label what concept or entity they refer to, often to distinguish it from other quantities with the same main symbol. These subscripts or superscripts tend to be written in upright roman typeface rather than italic while the main symbol representing the quantity is in italic. For instance E k or E kinetic is usually used to denote kinetic energy and E p or E potential is usually used to denote potential energy. Quantity reference: The quantity has a subscripted or superscripted single letter, group of letters, or complete word, to parameterize what measurement/s they refer to. These subscripts or superscripts tend to be written in italic rather than upright roman typefac...
Read more