Electronics >> Capacitors

Capacitor is an electronic component that in its basic form is constructed from two parallel conductive materials, separated by a dielectric (insulating) material. They are used in a circuit to store electrical charge. [Formula] [Capacitor symbols]

By connecting a capacitor to a DC voltage source we create a potential difference across the conductive plates of the capacitor. One plate of the component will be positively charged in relation to the other.


The capacitor's charging process is achieved by electrons moving through the voltage source and through the connecting leads to the conductive plate. This process will continue until the voltage across the leads of the capacitor is equal to the voltage of the DC source of the capacitor. (There is no flow of electrons through the dielectric part of the component during the charging process.)

When disconnected from the voltage source, a capacitor retains its charge for a period of time and it functions as a temporary battery within the circuit.

The measure for a capacitor's ability to store charge is called capacitance. Designated symbol (C).

Note: The symbol for capacitance is (C), and its unit is called Farad (F). The symbol for electrical charge is (Q), and its unit is called coulomb (C).

Description of the capacitance unit (Farad):

Farad is the amount of capacitance when one coulomb of charge is stored with one volt across a capacitor's plates.

By and large the values of capacitors used in most electronic circuits are in micro Farad (µF) or Pico Farad (pF).

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Capacitors could be polarized like Electrolytic Capacitors, or non polarized like Ceramic Capacitors.

Variable capacitors are also available and they are used in any circuits that require adjustable capacitance.

(e.g. Variable capacitors are used in radio tuner circuits.)

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