CAPACITORS

CAPACITORS

A capacitor is a 2 terminal passive component that is sometimes referred as condenser. It has the capacity to store energy in the form of electric charge that produces a potential difference across the two plates of the capacitor. The effect of capacitor that is its value is known as the capacitance of the capacitor.
The structure of capacitor consists of two parallel conducting plates which are separated from each other by the insulating material such as paper, plastic, electric gel, etc.
This insulation between the 2 plates of the capacitor is named the dielectric.

WORKING PRINCIPLE

The working principle of the capacitor is that the capacitance of a conductor increases considerably when an earthed conductor is brought near it.

WORKING
Now, when a DC voltage is applied across the capacitor, the positive charge quickly accumulates on one plate of the capacitor while a corresponding and opposite negative charge accumulates on the other plate of the capacitor. For every particle of charge that arrives at one plate a charge of an equivalent sign will depart from the negative plate.
As time goes on, positive plate will accumulate charge from the battery. After a particular time, the capacitor holds maximum amount of charge as per its capacitive value with reference to the voltage. This duration of time is called charging time.
The flow of electrons onto the plates of the capacitor is understood because the capacitors charging current which flows until the voltage across both plates is adequate to the applied voltage V cc. At this instant of your time the capacitor is claimed to be “fully charged”.
Now once we remove the battery from the capacitor, these two plates hold positive and charge for a particular time thus for that specific time, this capacitor acts as a source.
If the 2 ends of the capacitor gets shorted through a load, a current will flow through the load and every one the charge of the capacitor gets vanished. This time span is understood as discharging time of the capacitor.

STANDARD UNIT OF CAPACITANCE VALUE

· micro-farad(μF)  1 μF = 1/1,000,000 = 0.000001 = 10-6 F
· nano-farad (nF)  1 nF = 1/1,000,000,000 = 0.000000001 = 10-9 F
· pico-farad (pF)   1 pf = 1/1,000,000,000,000 = 0.000000000001 = 10-12 F

 

 

TYPE OF CAPACITORS

Generally there are four types of capacitors.
· Film capacitors: they're named for his or her dielectrics and have film coating over it.
· Mica capacitors: these capacitors uses mica like material as dielectric.
· Polarized capacitors: they need specific polarities like positive and negative.
· Electrolytic capacitors: they're the sort of capacitors that are polarized, and are ready to offer capacitance value of high range.
· Ceramic capacitors: they need ceramic dielectric and haven't any polarity.
· Special Purpose capacitors:
· Double-layer capacitors were named for the natural phenomenon of the Helmholtz double-layer
· Pseudo capacitors were named for his or her ability to store electric energy electro-chemically with reversible farad charge transfer.
· Hybrid capacitors combine double-layer and pseudo capacitors to extend power density.
· Silver mica, glass, silicon, air-gap and vacuum capacitors are names for this capacitor..

APPLICATIONS

· Decoupling capacitors
· Power supply filtering
· Energy storage and supply
· Signal filtering
· Tuning (in radio system)
· Oscillators