Electrical engineering - Basics Page 25

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4.2 Capacitors as electric components

Capacitors store electric charges. Many different types of capacitors exist. However, they all have the same basic structure: They consist of two electric conductors with an insulator (the dielectric) between them.
In the four diagrams below the function of a capacitor is described:

Diagram 27: Uncharged capacitor

The capacitor plates are electrically neutral. On each capacitor plate the same number of positive and negative charges exists.
Diagram 28: Charging process

For a short period of time a current is flowing over the supply lines. The positive pole is extracting electrons from the capacitor plate 1 whereas the negative pole is pressing additional electrons on the capacitor plate 2. The capacitor voltage is increasing.
Diagram 29: Charged capacitor

In charged state the capacitor voltage is just as high as the voltage of the voltage source. No more current is flowing anymore. In this state the capacitor functions like an insulator. However, it is storing the charges.
Diagram 30: Discharging process

If the voltage source is being removed and if afterwards one connects the two capacitor plates with a resistor the stored charges are compensating themselves. The capacitor charge sinks down to zero.


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