SI units
SI units (Système International d'Unités) The international system of units of measurement which evolved over a number of years from the m.k.s. system (based on the metre, kilogram, and second) and was finally adopted in 1960 by the 11th Conférence Générale des Poids et Mesures. The system is widely used in trade and is recommended for all scientific work. There are seven basic units: metre (m, length); kilogram (kg, mass); second (s, time); ampere (A, electric current); kelvin (K, thermodynamic temperature); candela (cd, luminous intensity); and mole (mol, amount of substance). There are also two supplementary units: radian (rad, plane angle); and steradian (sr, solid angle). From these, a further 18 units are derived: hertz (Hz, frequency); joule (J, energy); newton (N, force); watt (W, power); pascal (Pa, pressure); coulomb (C, electric charge); volt (V, electric potential); ohm (Ω, electric resistance); siemens (S, electric conductance); farad (F, electric capacitance); weber (Wb, magnetic flux); tesla (T, magnetic induction); lumen (lm, luminous flux); lux (lx, illuminance); gray (Gy, absorbed radiation dose); becquerel (Bq, radioactivity); and sievert (Sv, radiation dose equivalent). See Derived SI units.
Quantity | Name of unit | Symbol | Equivalent | Reciprocal |
|---|---|---|---|---|
length | metre | m | 3.281 feet | 1 ft = 0.3048 m |
mass | kilogram | kg | 2.2 pounds | 1 lb = 0.454 kg |
time | second | s | ||
ampere | A | |||
thermodynamic temperature | kelvin | K | 1°C = 1.8°F | 1°C = 1 K |
luminous intensity | candela | cd | ||
amount of substance | mole | mol |
Quantity | Unit | Symbol |
|---|---|---|
plane angle | radian | rad |
solid angle | steradian | sr |
More From encyclopedia.com
NEARBY TERMS
SI units