In electric circuits, capacitors are used to store energy for flash lamps, to provide a tuning mechanism for radios, and to perform various other useful tasks.
This device consists of two metallic surfaces or plates separated by a dielectric.Ideally , the perfect dielectric is insulator,so that it prevents charge flow inside the capacitor.
When a voltage source is attached to a capacitor an electric field is created between the plates. This field holds the energy supplied by the source to move the charges.so
A capacitor stores energy in an electric field produced by displaced charge on the plates.Mathematically,
q= C v where the proportionality constant C is called the capacitance,defined as
C= q/v
Capacitance is measured in farads(F),named in the honour of English experimentalist Michael Faraday(1791-1867).
TYPES OF CAPACITORS:
Capacitors come in a wide variety of shapes and sizes.Particular families are categorized according to the type of dielectric material.some capacitors often consist of thin ceramic disks with metal coatings on the plat surfaces to from the plates.
Larger capacitances are achieved by rolling sheets of metal foil and flexible dielectric into a tubular shape.The dielectric is usually a plastic film such as mylar.
For,
Air variable capacitor's capacitance is 10-500 pF, voltage is 500 and RC is Infinity.
Ceramic disk capacitor's capacitance is 5 pF-50 nF, voltage is 600-1000 and RC is 1000.
Plastic film capacitor's capacitance is 1 nF-5 uF, voltage is 100-600 and RC is 100,00.
Electrolytic capacitor's capacitance is 1 uF-1 F, voltage is 6-250 and RC is 50-500.
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