Construction and Types:
The capacitor consists of two conducting plates that are separated by an insulating medium known as the dielectric. The capacitance is dependent upon the surface area of the plates, the distance between the dielectric medium and the dielectric constant of the object. The greater the area of the plates, the closer they are together and greater the value of the dielectric constant the greater is the value of capacitance. High capacitance capacitors are now available in small size. This has been achieved employing a number of techniques like having several sets of plates, placing the plates very close to one another, having a thin layer of dielectric placed between them and developing special insulating dielectric materials.
The capacitance of a capacitor is also affected by the shape or structure of the capacitors. The capacitors are available in different shapes like radial lead type which are rectangular or cubical or axial lead type which are tubular or cylindrical.
The variable type of capacitors can vary the capacitance by changing the distance between the plates or the effective area of the capacitor.
The polarized type of capacitors should be connected as per their polarity or else the capacitor can be damaged due to incorrect connection.
The low value capacitors are non-polarized and can be connected in any manner. They are not damaged by heat when soldering, except for the polystyrene type of capacitor. They have high voltage ratings of at least 50V, usually 250V or so
Many small value capacitors have their value printed but without a multiplier, so you need to use experience to work out what the multiplier should be!
· 0.1 means 0.1µF = 100nF.
Sometimes the multiplier is used in place of the decimal point:
For example - 4n7 means 4.7nF.
The various types of capacitors are given below:
1. Fixed capacitors
· Film Capacitors like glass capacitor, mica capacitors, silver mica capacitor, ceramic capacitor, paper capacitor, metalized paper capacitor, polyester capacitor, polystyrene capacitor, metalized polyester capacitor, polycarbonate capacitor, polypropylene capacitors, Teflon capacitors, porcelain capacitor.
· Electrolyte Capacitors like aluminum electrolyte, tantalum electrolyte, aluminum-tantalum electrolyte
2. Variable capacitors