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Electrical Engineering: Know It All by Dan Bensky, Walt Kester, Tim Williams, John Bird, Clive Maxfield

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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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