Newnes Circuit Calculations Pocket Book

2 Resistors

2.1 Introduction

Metals offer very little resistance to the flow of current. Copper is a

good example and is referred to as a conductor. Other materials

such as quartz, polythene and procelain offer very high resistance to

the flow of current and are called insulators.

Intermediate between conductors and insulators are semi-

conductors, the most important being silicon and germanium used

in the manufacture of transistors. Materials made into rods, films

and wire form electronic components which are called resistors.

2.2 Units

The unit of resistance, R, is the ohm, which has the symbol O

(Greek letter omega). The main units are: