1.1 CapacitorsA capacitor is a device contained in an electrical circuit, which stores an electrical charge. They are commonly used in computers, televisions and all electronic circuits such as car ignition circuits and some power tools. They play an important role in electronic circuits, so without capacitors, electronic circuits will be limited. Capacitors do not have the ability to conduct an electrical charge like other circuit components do, but can store electrical charge, making them very useful and unique from other devices. If the capacitors were to conduct electrical charge, no charge would be stored, because the two oppositely charged plates will fail to separate and will then attract each other. Capacitors that begin to conduct in a circuit are defective and must be removed because they do not store any charge (John. 1989). 1.1.1 Practical Capacitors Practical capacitors are designed using two metal plates that are closely bonded but not touching. The two metal plates are oppositely charged, one is positively charged (+Q) and the other is negatively charged (-Q). The total charge on the capacitor is actually just Q because charge Q flows through a circuit when the capacitor is disconnected. Preventing the two charged metal plates from meeting and neutralizing each other is due to the use of an insulating material that keeps them separated from each other. Examples of such capacitors are: a) Metal foil capacitors consist of two lengths of metal foil separated by sheets or films of plastic insulating material wound tightly into a cylinder and encapsulated for protection. The lengths of the foil are each connected to one end of the plate which is oppositely charged and the wiring...... middle of paper ...... rial plays an important role with different functions to operate the well capacitor (Ramasamy. 2005).a) Electrodes: are thin sheets of 6 mm in length made of self-annealed pure aluminum foil. Two electrodes are used in each single-phase capacitor. One electrode is positively charged, while the other is negatively charged.b) Dielectric material: Insulating material used to separate the electrodes, for example polypropylene.c) A Housing, dielectric fluid and bushing: Container in which the electrodes made of aluminum and the dielectric material are placed and where insulation is ensured. Dielectric fluid is used to fill the housing. The housing is sealed and the electrodes are terminated with a porcelain socket when high voltage capacitors are used. d) Discharge resistors: these are connected to the electrodes to discharge the capacitor when disconnected from the source..