TABLE OF CONTENTS Mike Tooley
Darren Ashby
Robert Pease
This chapter has been designed to provide you with the background knowledge required to help you understand the concepts introduced in the later chapters. If you have studied electrical science, electrical principles, or electronics then you will already be familiar with many of these concepts. If, on the other hand, you are returning to study or are a newcomer to electronics or electrical technology this chapter will help you get up to speed.
You will already know that the units that we now use to describe such things as length, mass and time are standardized within the International System of Units (SI). This SI system is based upon the seven fundamental units (see Table 1.1).
| Quantity | Unit | Abbreviation |
|---|---|---|
| Current | ampere | A |
| Length | meter | m |
| Luminous intensity | candela | cd |
| Mass | kilogram | kg |
| Temperature | Kelvin | K |
| Time | second | s |
| Matter | mol | mol |
All other units are derived from these seven fundamental units. These derived units generally have their own names and those commonly encountered in electrical circuits are summarized in Table 1.2, together with the corresponding physical quantities.
| Quantity | Derived unit | Abbreviation | Equivalent (in terms of fundamental units) |
|---|---|---|---|
| Capacitance | farad | F | A s V ?1 |
| Charge | coulomb | C | A s |
| Energy | joule | J | N m |
| Force | newton | N | kg m s ?1 |
| Frequency | hertz | Hz | s ?1 |
| Illuminance | lux | lx | lm m ?2 |
| Inductance | henry | H | V... |
