capacitor working principles
capacitor working principles
The capacitor is the essential component of any circuit design. And in fact, after the resistor, it is the second most used passive component in the circuits. Now, these capacitors are available in various size, types and shapes.
Various types of capacitors
Types of Capacitors
Overview of Different Types of Capacitors

Ceramic capacitor

Electrolytic capacitor

Tantalum capacitor

Silver Mica Capacitor

Polystyrene Film Capacitor

Polyester Film Capacitor

Metallised Polyester Film Capacitor

Polycarbonate Capacitor

Polypropylene Capacitor

Glass Capacitors

SuperCap
Energy store across capacitor
The basic function of any capacitor is to store electrical energy. So, now in this article, let understand how does this capacitor work and how the energy is stored across this capacitor.
Now, capacitor consists of two conductive plates which are separated by a dielectric material. Now, this dielectric material is the insulating material and it opposes the flow of current.
So, now let understand when we apply the voltage to this capacitor then how the energy is stored across this capacitor. Now, before the application of voltage, the two conducting plates of this capacitor are electrically neutral. It means that it has the equal amount of positive as well as the negative charge.
Voltage is applied to this capacitor
But once the voltage is applied to this capacitor, then from the top plate the electrons or the negative charge is attracted towards the positive terminal of this battery. And through the negative terminal of the battery, the electrons are pushed towards the bottom plate of this capacitor. Now, because of the dielectric material between the two plates electrons which are collected at the bottom plate of this capacitor are not able to cross this barrier. And because of that, you will observe that over the period of time the electrons will get accumulated at the bottom plate of this capacitor.
So, over the period of time, the top plate will have a shortage of electrons, while the bottom plate will have excessive electrons. Or we can say that the top plate will get positively charged, while the bottom plate will get negatively charged. And because of the charged particles, the potential difference will get developed across the two plates.
Potential difference
The building of charges across the two plates will continue till the point the potential difference that is developed across the two plates is equal to the supplied voltage. because of this potential difference, the electric field will get developed across the two plates. And this developed electric field is directly proportional to the potential difference and it is inversely proportional to the distance between the two plates. So, smaller the distance between the two plates, the stronger will be the electric field. So, in this way, when we apply the voltage to the capacitor, then the charges are developed across the two plates of this capacitor and because of the development of the charge, the electric field is developed between the two plates.
Capacitor stores energy
The capacitor stores the energy in form of this electric field. Now even if we remove this voltage source, then also the charges that are developed across the two plates will remain as it is. So, unless we apply the conductive path to this capacitor, the charges that are developed across the two plates will remain as it is. So, the conductive path is connected between the two terminals of this capacitor. And load in the form of the bulb is connected to this conductive path. So, now whenever we turn on this switch at that time, the electrons from the bottom plate will get attracted towards the top plate. And in this way, the transfer of charge or flow of current through this conductive path. So, now because of the flow of current, you will see that the bulb will grow. And in this way, the current will flow through this conductive path. And this procedure will continue till both the plates will become electrically neutral. So, over the period of time, you will observe that both plates will become electrically neutral.
And there will not be any flow of electrons through this conductive path. And because of that, the bulb will again turn off. So, in this way, the charge that was developed across the capacitor has been discharged through this conductive path. And this phenomenon can be known as the discharging of the capacitor. Now, the ability of the capacitor to store the charge is known as the capacitance. And it is represented as the charge that is developed across the capacitor per unit voltage. And generally, it is denoted by the unit of Farad.
Now, this farad is a very big unit and usually, it is not used to define the capacitance. Rather very small units like mF, uF and pF are used to define the capacitance. So, now for the given capacitance if you want to store the more charge across the capacitor then you need to apply the more voltage across that capacitor. Or for the given voltage suppose if you want to store the more charge across the capacitor, then you need to select the capacitor in a such a way that it has a large capacitance. So, as you can see over here, by changing the applied voltage we change the amount of charge that is stored across the capacitor. But here we can not increase the voltage indefinitely. So, for every capacitor, you will find that the maximum voltage rating has been defined. So, the voltage that is applied across the capacitor should be less than that maximum rating.
Discharge of capacitor
So, if the applied voltage is greater than the maximum rated voltage, in that case, you will see the dielectric breakdown in the capacitor. So, now let see the factors which affect the capacitance of this capacitor.
So, there square measure 3 factors that have an effect on the capacitance of this electrical device. The first is the area of the plates. then the second issue is that the distance between the 2 plates of this electrical device. And the third issue is that the permittivity of the insulator material. And the relation between 3 may be given by this expression.
That is C is equal to So, as you can see over here, the capacitance of this capacitor is directly proportional to the area of the plate as well as the permittivity of this dielectric material. And it is inversely proportional to the distance between the plates.
So, now let see, how these factors can affect the capacitance of this capacitor. So, the first factor is the area of these plates. So, because the space of the plates will increase, the quantity of charge which will be keep across the plates will increase. And in a very manner, canwe are able to} say that the capacitance of the electrical device will increase. Now, the second factor which affects the capacitance is the distance between the two plates.
So, now as the distance between the two plates reduces, the electric field that is developed across the two plates will also increase. Because it is inversely proportional to the electric field. And as this electric field increases, the charge that can be stored across the capacitor will also increase.
Effect of die electric materials
The third issue that affects the capacitance is that the permittivity of the insulator material. Now, this permittivity can be defined as the product of absolute permittivity and the relative permittivity. Where this relative permittivity is additionally referred to as the insulator constant of the fabric. So, owing to this insulator material, the capacitance of the capacitor will increase. So, now let understand how this dielectric material affects the capacitance of the capacitor. Now, like I said before, this dielectric material is the insulating material.
So, it will not allow the flow of current. But this dielectric material has polar molecules. It means whenever there’s no field of force, in that case, these molecules are aligned randomly .But whenever the external electric field is applied, in that case, these molecules aligned themselves according to the electric field. So, at the top edge of the dielectric material, if you see, you will find the negative charges. While at the bottom end of this dielectric material you will find the positive charges. Now, these charges develop its own electric field, which opposes the electric field that is generated by the capacitor.
So, owing to this insulator material, the effective electric field of the capacitor will reduce. And in a very manner, we can say that the potential difference that is generated across the two plates will also reduce, provided the charges that are developed across the two plates are constant. So, therein case, to increase the potential we require the more amount of charge across the two plates.
So, in a way, we will say that, because of the introduction of this dielectric material, the capacitor can more amount of charge. Or canwe are able to} say that the capacitance of the electrical device will increase. So, these square measure the 3 factors that have an effect on the capacitance of this electrical device.
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