Type of Capacitor and Leakage Current

Types of Capacitors

Capacitors like resistors can be listed under two general headings fixed and variable. The symbol for the fixed capacitor appears in , Note that the curve side is normally connected to ground or to the point of lower dc potential. The symbol for variable capacitors appears.


Fixed Capacitors Fixed-type capacitors come in all shapes and sizes.
 However,

    In general for the same type of construction and dielectric the larger the required capacitance , the larger the physical size of the capacitor.

In the 10000microferad electrolytic capacitor is significantly larger than the 1microferad capacitor. However it is certainly not 10000 times larger. For the polyester film type of the microfarad capacitor is significantly larger than 0.01 microfarad capacitor but again it is not 220 times larger. The 22microfarad tantalum capacitor is about 6 times larger than the 1.5microfarad even though the capacitance level is about 15 times higher.It is particular interesting to note that due to the difference in dielectric and construction the 22 microfarad polyester-film capacitor. The relatively larger than  10000 microfarad electrolytic capacitor is normally used for high power application, such as in power supplies and high output speaker systems.

 In general the most common fixed capacitors are the electrolytic film polyester foil ceramic , mica , dipped and oil.

   Electrolytic Capacitor 

The electrolytic capacitors in are usually easy to identify by there shape and the fact  that the usually  have a polarity marking on the body. Few capacitors have a polarity marking but those that do must be connected to ground or to the point of lower potential. The markings often used to denote the positive terminal or place include +, square and dell. In general electrolytic capacitor.

The size of the roll of aluminum foil the overall size of the electrolytic capacitor is greater than most .

Film, polyester, foil, polypropylene or teflon capacitor use a rolling or stacking process to increase the surface area, as shown the resulting shape can be either round or rectangular with radial axial leads.

       Mica Capacitor

Mica capacitors use a mica dielectric that can be monolithic or stacked. The relatively small size of monolithic mica chip capacitors is demonstrated with their placement shown. A variety of high voltage mica paper capacitors are displayed. Mica capacitors typically range in value from 2pF to several micro-farads with working voltages up to 20 kv.

         Dipped Capacitor

Dipped capacitors are made by dipping the dielectric into a conductor in a molten state to from a thin , conductive sheet on the dielectric. Due to the presence of an electrolytic in the manufacturing process dipped tantalum capacitors require a polarity marking to ensure that that the positive plate always at a higher potential than the negative plate as shown. They typically range in value from 0.1 microfarad to 680 microfarad, but with lower working voltage ranging from 6v to 50v.


          Ceramic Capacitor

Ceramic capacitors use a ceramic dielectric as shown to utilize the excellent epsilon values and high working voltage associated with a number of ceramic materials.Ceramic capacitors typically range in value form 10 pF to 0.047microfaraad with high working voltage that can reach as high as 10 kv.

            Most Oil Capacitor 

Most oil capacitors such as appearing are used for in dust-rial application such as welding , high  voltage power supplies surge protection and power factor correction.They can provide capacitance levels extending from 0.001 microfarad all the way up to 10000 microfarad with working voltage 150kv.


             Variable Capacitor

Variable capacitors all the parameters can be changed to some degree to create a variable capacitor.
For example in the capacitance of the variable air capacitors is changed by turning the shaft at the end of the unit.By turning the shaft you control the amount of common area between the plates. The less common area there is the less capacitance. We have a much smaller air trimmer capacitor.

          Ceramic Trimmer Capacitor

Ceramic trimmer capacitor permits varying the capacitance by changing the common area as above or by applying pressure to the ceramic plate to reduce the distance between the plates.