ABSTRACT
At the end of this chapter you should be able to:
• appreciate some applications of capacitors
• describe an
• define electric field
• define capacitance
• describe a capacitor symbol
• perform simple
andQ = It • define electric flux
• define permittivity, r and ε
• perform simple = V
D and
D
E =ε0εr
• understand that for a = ε0εrA(n− 1) d
• perform calculations involving capacitors connected in parallel and in series
• define dielectric strength and state its unit
• state that the energy stored in a capacitor is given byW = 12 CV2 joules • describe practical types of capacitor
• understand the precautions needed when discharging capacitors
A capacitor is an electrical device that is used to store electrical energy. Next to the resistor, the capacitor is the most commonly encountered component in electrical circuits. Capacitors are used extensively in electrical and electronic circuits. For example, capacitors are used to smooth rectified a.c. outputs, they are used in telecommunication equipment – such as radio receivers – for tuning to the required frequency, they are used in time delay circuits, in electrical filters, in oscillator circuits and in magnetic resonance imaging (MRI) in medical body scanners, to name but a few practical applications. Some typical small capacitors are shown in Figure 8.1.
