Chapter 1
An Introduction to Electric Circuits
John Bird
1.1 SI Units
The system of units used in engineering and science is the Système International d’Unités (International system of units), usually abbreviated to SI units, and is based on the metric system. This was introduced in 1960 and is now adopted by the majority of countries as the official system of measurement.
The basic units in the SI system are listed with their symbols, in Table 1.1.
Table 1.1
Basic SI units
| Quantity | Unit |
| length | meter, m |
| mass | kilogram, kg |
| time | second, s |
| electric current | ampere, A |
| thermodynamic temperature | kelvin, K |
| luminous intensity | candela, cd |
| amount of substance | mole, mol |
Derived SI units use combinations of basic units and there are many of them. ...
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