SI stands for the ‘Système lnternational (SI) D’Unités’, which translates from the French as the ‘International System of Units’ Represent a set of fundamental base units, derived units and prefixes used throughout the world: Based on metric units with the...

Unit Second Metre Mole Ampere Candela Kilogram Kelvin Unit Symbol s m mol A cd kg K Base Measure Time Length Amount of Substance Electric Current Luminous Intensity Mass Temperature MEMORY TIP Can be remembered by the acronym ‘SMMACKK’ S econd M etre M ole...

Unit Second Unit Symbol s Base Measure Time Physical Constant Hyperfine transition frequency of caesium (ΔνCs) Definition The time taken by 9,192,631,770 oscillations of the light emitted by a caesium-133...

Unit Kilogram Unit Symbol kg Base Measure Mass Physical Constant Plancks Constant (h) - relationship between a photons energy and frequency Definition Defined by taking Plancks constant (h) to be a fixed numerical value of 6.62607015×10−34...