The international system (SI) unit represent a rationalised selection of the MKS system of units which has been universally used by scientists for many years. Once the three basic MKS units – metre, kilogram and second – are defined, we can derive all additional units that we might need in mechanics from these base units.
By defining one additional base unit – the ampere – we can derive all the units required for electrical measurement. In order to relate electrical measurements to mechanical measurements, the ampere is defined in terms of the electromagnetic force between two current carrying electric conductors.
