Electrical and Electronic Principles and Technology

The system of units used in engineering and science is the Système Internationale d’Unités (International sys- tem 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 below with their symbols:

The unit of electric potential is the volt (V), where one volt is one joule per coulomb. One volt is defined as the difference in potential between two points in a con- ductor which, when carrying a current of one ampere, dissipates a power of one watt, i.e.

The unit of electric resistance is the ohm(), where one ohm is one volt per ampere. It is defined as the resistance between two points in a conductor when a constant electric potential of one volt applied at the two points produces a current flow of one ampere in the conductor. Thus,