Capacitors
A capacitor stores electrical energy when charged by a DC source. It can pass alternating currents (AC), but blocks direct currents, called transient currents.
Capacitors, How are they made?
There are many different types of capacitors used in electronic. Each type is made from different materials and with different methods. Capacitors are also made to handle different amounts of electrical pressure or voltage. Each capacitor is marked to show the maximum voltage that it can withstand without breaking down.
The metal foil capacitor
Perhaps the most common form of capacitor is constructed by tightly winding two foil metal plates that are separated by sheets of paper or plastic. By picking the correct insulating material the value of capacitance can be increased greatly.
Dielectric constant, What is it?
The Dielectric in a capacitor is the material that can withstand electrical pressure without appreciable conduction. When a voltage is applied to a capacitor, energy in the form of an electric charge is held by the dielectric. In the rubber would stretch out and hold the water back. The energy was stored in the rubber. When the plunge is released the rubber would release this energy and push the plunger back toward its original position.
The variable capacitor
To make a variable capacitor, one set of stationary aluminum plates are mounted to a frame with a small space between each plate. Another set of plates are mounted to a movable shaft and designed to fit into the space of the fixed plates without touching them. The insulator or dielectric in this type of variable capacitor is air.
Capacitors, How is it calculated?
The amount of charge a capacitor can hold is measured in Farads. In practice, one farad is a very large amount of capacitance, making the most common term used micro-farad or one millionth of farad. There are three factors that determine the capacitance that exist between two conductive plates