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A capacitor is a two-terminal electrical device. It can store energy in the form of an electric field, which generates a potential difference, i.e, the static voltage across its plates. It is way too similar to a small rechargeable battery. Numerous dissimilar capacitors are available, from very tiny capacitor beads used with the resonance circuits to huge power factor correction capacitors. However, they all function similarly as all of them store the charge.
Capacitors comprise two or more parallel conductive metal plates in their basic form. These plates are not linked, and they don’t even touch each other. However, it is separated electrically, either through the air or through a decent insulating material like waxed paper, ceramic, mica, some type of liquid or plastic, as used with the electrolytic capacitors. Usually, the insulating layer amid capacitor plates is known as the dielectric.
The capacitance of a capacitor
The capacitance is referred to as the chemical property of a capacitor. It also measures a capacitor’s ability to store the electric charge in its two plates with farad as the capacitance unit. The name ‘farad’ has been derived from physicist Michael Faraday’s surname.
The capacitance can be defined as a capacitor that comes with the capacitance of 1 farad when a charge of 1 coulomb is stored on the plates through 1-volt voltage. Moreover, capacitance C is always positive in the value, and the negative units are absent. However, the farad is a way too big a unit of measurement for use on its own. Therefore, the sub-multiples of farad are usually used like nano-farads, micro-farads, and picofarads.
Standard units of capacitance
The capacitance of a parallel plate capacitor
The parallel plate capacitor’s capacitance is proportional to the area A in metres, and inversely proportional with the distance or separation d, ie, the dielectric thickness provided in metres amid these two conductive plates.
Moreover, the general equation for the parallel plate capacitor’s capacitance is known as
C = ε(A/d).
Here, ε shows the utter permittivity of the dielectric material being utilised. Furthermore, the dielectric constant εo is also called the permittivity of free space, comprising the constant 8.854 x 10-12 farads/metre value.
To make the mathematics a bit easier, this free space’s dielectric constant εo can also be written as 1/(4π x 9×109), and it may also comprise the units of pF, ie, picofarads/metre as the constant that gives 8.85 for the value of free space.
Moreover, the outcome as the capacitance value will be in picofarads and not in farads. Usually, a capacitor’s conductive plates are separated by some type of insulating material or a gel despite a perfect vacuum. While calculating the capacitance of a capacitor, the permittivity of air can be considered, especially of the dry air, as being the same value as a vacuum as they are way too close.
A capacitor’s voltage rating
Every capacitor has a maximum voltage rating. While selecting a capacitor, consideration should be given to the voltage amount to be applied across the capacitor. Moreover, the utmost amount of voltage applicable to the capacitor without causing any damage to its dielectric substance is usually provided in the datasheet as WV or working voltage – also known as WV DC, ie, DC working voltage.
Furthermore, if the voltage increases too much while being applied across the capacitor, then the dielectric will break down as well as the arcing will take place amid the capacitor plates resulting in a short-circuit. Notably, the working voltage of the capacitor depends on the kind of dielectric material used and its thickness.
Uses and applications of capacitors
We can use the capacitors in various ways, such as circuits, blocking ACs, etc. This capability of the capacitor to block the ACs, lets the capacitor be used for smoothing the output voltages of power supplies. The capacitor can also be used to supply power to remove the unwanted spikes from the signals, or else that would tend to result in damage or false triggering of the digital components or the semiconductors.
Conclusion
A capacitor is a two-terminal electrical device. It is a type of device that possesses the ability to store energy in the form of an electric field. Moreover, it consists of two electrical conductors separated by a distance. A capacitor has two basic functions – charging as well as discharging. It works in both AC as well as DC circuits.
