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Capacitors Operation and Construction

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Capacitors Operation and Construction

A capacitor is a passive two-terminal electrical component that stores potential energy in an electric field. The effect of a capacitor is known as capacitance. While some capacitance exists between any two electrical conductors in proximity in a circuit, a capacitor is a component designed to add capacitance to a circuit. The capacitor was originally known as a condenser.

The physical form and construction of practical capacitors vary widely and many capacitor types are in common use. Most capacitors contain at least two electrical conductors often in the form of metallic plates or surfaces separated by a dielectric medium. A conductor may be a foil, thin film, sintered bead of metal, or an electrolyte. The nonconducting dielectric acts to increase the capacitor's charge capacity. Materials commonly used as dielectrics include glass, ceramic, plastic film, paper, mica, and oxide layers. Capacitors are widely used as parts of electrical circuits in many common electrical devices. Unlike a resistor, an ideal capacitor does not dissipate energy.

When two conductors experience a potential difference, for example, when a capacitor is attached across a battery, an electric field develops across the dielectric, causing a net positive charge to collect on one plate and net negative charge to collect on the other plate. No current actually flows through the dielectric, however, there is a flow of charge through the source circuit. If the condition is maintained sufficiently long, the current through the source circuit ceases. However, if a time-varying voltage is applied across the leads of the capacitor, the source experiences an ongoing current due to the charging and discharging cycles of the capacitor.

CAPACITORS - Department of Defense 1964 - PIN 39987 - DEFINES ELECTROSTATIC FIELD AND DIELECTRIC. DESCRIBES AIR, PAPER, OIL, ELECTROLYTIC, AND CERAMIC TYPE CAPACITORS AS TO THEIR CONSTRUCTION AND GENERAL USAGE. THE UNIT FOR MEASURING CAPACITORS, THE "FARAD", IS STATED AND EXAMPLES OF COMPUTING CAPACITANCE ARE GIVEN. THE FACTORS OF DIELECTRIC, PLATE AREA, AND DISTANCE BETWEEN PLATES WHICH AFFECT THE VALUE OF CAPACITANCE ARE PRESENTED, AND THE NARRATOR DISCUSSES THEIR EFFECTS ON CAPACITANCE. DEFINES VOLTAGE RATING AND EXPLAINS THE FACTORS WHICH AFFECT THE VOLTAGE RATINGS OF CAPACITORS.



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