Prof. Dr. Thorsten Jungmann (last updated 2025-08-17)
The International System of Units (‘Système international d’unités’, SI) is the foundation of all physical measurements and is therefore also indispensable for electrical engineering. It defines seven base units.
The following base quantities are used directly in this script:
The remaining three base quantities do not appear explicitly in the formulas in this script, but they play an indirect role:
Further quantities can be derived from the base units. For example, voltage is formed as a derived unit from the base units kilogram, metre, second and ampere.
Thanks to this uniform system, the SI system enables clear definitions, international comparability and precise calculations in all areas of electrical engineering. The SI prefixes also serve this purpose.