Essay On Capacitors

1.1 Capacitors
A capacitor is a device contained by an electric circuit, which stores electric charge. They are commonly used in computers, televisions and all electronic circuits such as car ignition circuits and some electric power tools. They play a significant role in electronic circuits, such that without capacitors the will be a limitation of electronic circuits. Capacitors do not have the ability to conduct electric charge like other components of the circuit do, but can store the electric charge and that makes it very useful and unique from other devices. If the capacitors were to conduct the electric charge no charge would be stored, as the two oppositely charged plates will fail to keep separate and then attract each other. Capacitors which start to conduct in a circuit have a fault and must be removed as they will not store any charge (John. 1989).
1.1.1 Practical capacitors
Practical capacitors are designed using two metal plates held closely together but not touching each other. The two metal plates are oppositely charged, one is positively charged (+Q) and the other is negatively charged (-Q). The total charge of the capacitor is effectively just Q because charge Q flows round a circuit when the capacitor is disconnected. The prevention of the two metal charged plates from meeting and neutralising each other is due to the use of insulating material which keep them separate from each other. Examples of such capacitors are:
a) Metal foil capacitors consist of two lengths of metal foils separated by sheets or films plastic insulating material rolled up tightly into a cylinder and encapsulated for protection. The lengths of the foil are each connected to one end of the plate which are oppositely charged and the wiring ...

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...rial play an important role with different functions to make the capacitor to operate well (Ramasamy. 2005).
a) Electrodes: Are thin sheets of 6mm in length of pure-self annealed aluminium foil. Two electrodes are used in every single-phase capacitor. One electrode is positively charged, while the other is negatively charged.
b) Dielectric material: Insulating material used to separate the electrodes e.g Polypropylene.
c) A Case, dielectric fluid and bushing: Container in which the aluminium electrodes and dielectric material are placed and where insulation is provided. The dielectric fluid is used to fill the case. The case is sealed and the electrodes are terminated through porcelain bushing, when capacitors with high voltage are used.
d) Discharge resistors: They are connected to the electrodes to discharge the capacitor when it is disconnected from the source.