Capacitors
CapacitorsCapacitors
A device for storing an electrical charge is called a capacitor or electrical condenser. Capacitors in their simplest form consist of two metal plates, which are separated by a nonconducting layer called the dielectric. As one plate gets charged with a direct- current such as a positive charge, the other plate will be charged with the opposite sign such as a negative charge. The larger the capacitor, the more electrically charge it can absorb. Capacitors are limited to the amount of electrical charge, but they function well as conductors in alternating- current circuits. One example of this is called the Leyden jar, which has the two plates that are coated with a metal- foil on both sides. The coated plates sit in a glass jar, which then acts as a dielectric.
Capacitors are produced in a wide variety of forms. Each form has a different purpose, but they all seem to do the same thing. Capacitors are generally classified according to the kind of dielectric used in them. The capacitance of a capacitor is measured in farads. A farad retains one coulomb of charge with one-volt difference of potential. Capacitors that use vacuum, air, or other gases are used in applications where values of capacitance required do not have to be large, but the energy loss in the dielectric must be very small. Some applications for these capacitors are in radio- frequency circuits and low- frequency measuring circuits where great precision is required. Another type of capacitor uses castor or mineral oil for the dielectric. Oil insulated...
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