Newnes Circuit Calculations Pocket Book

7 Capacitors

7.1 Introduction

The capacitor shown in Figure 7.1 consists of two metal plates

separated by an insulator. It can store electricity, with a negative

charge on one plate and a positive charge on the other. The

insulator is referred to as a dielectric. Some common dielectrics are

air, paper, mica, bakelite, glass, rubber and porcelain. The quantity

symbol for capacitance is C, and the unit symbol is the farad, F.

Multiple plate capacitors also exist. The most common is the

variable capacitor used for tuning radio receivers. The behaviour of

capacitors in d.c. and a.c. circuits is dealt with in Chapters 9 and 11

respectively.

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