A dielectric is an insulator that separates the two plates or sheets of the conductor on the capacitor. Isolators are materials that cannot conduct the electric current, for example, plastic, glass, paper, or wood. The dielectric function is to increase the capacitance so that the capacitor can store more electric charge and the electric potential energy.
A capacitor can function if both conductor plates do not touch each other so that the electric charge does not move from one conductor to another. Likewise, so that the electric charge does not move from the conductor to the air, the space between the two conductors must be a vacuum. In the topic about the parallel plate, the capacitor has been discussed the capacitance of parallel plate capacitors which are separated by a vacuum. The capacitance of the capacitor in a vacuum has limitations so that to enlarge the capacitance, placed dielectric between the two plates.
The dielectric increases the capacitance because the electric potential between the two conductor plates decreases
Why is the capacitance of the capacitor increased after the dielectric is placed between the two plates or sheets? To find out the answer to this question, first, remember the lesson about the electric charge. Like electric charge repel each other, while unlike electric charge attract each other. For example, a positive charge attracts a negative charge but rejects a positive charge. Then why can negatively charge plastics attract small pieces of paper that are not electrically charged? This happens because the piece of paper experiences charge polarization.
Electrons in insulating materials such as paper cannot move freely as electrons in the conductor materials. So, when the negatively charged plastic is brought close to the piece of paper, the electrons that are bound to the atom are rejected away from the negatively charged plastic. So that there is the polarization of the negative charge and positive charge on the paper. The negative charge on paper is farther away from plastic, while the positive charge on paper has a distance closer to plastic. Then, the negative charge on the plastic pulls the positive charges on the piece of paper until the paper moves closer to the plastic.
The polarization process of charge that occurs on pieces of paper is similar to the polarization of charge that occurs in the dielectric. As shown in the figure on the left side, for example, at first, there were only two pieces of electrically charged conductors. The left plate is positively charged while the right plate is negatively charged so that the direction of the electric field is from left to right.
After the dielectric is placed between the two conductor plates, the positive charge on the left plate pulls the electrons on the nearby dielectric surface. As well as, the negative charge on the right plate repels the electrons on the nearby dielectric surface. The electrons in the dielectric, which is an insulator, are not free to move like electrons in a conductor. Therefore, electrons remain bound to the atom, but there is a polarization of negatively charged electrons and positively charged protons, as shown in the figure.
The presence of a positive charge on the right side of the dielectric atoms and a negative charge on the left side of the dielectric atoms gives rise to an electric field. Which is from right to left, which weakens the electric field generated by the electric charge on the conductor plate, which is from left to right. So, the electric field decreases not because the electrical charge on the two plates/sheets of the conductor decreases, but because the electric field appears in the dielectric in the opposite direction. If the dielectric is released, the electric field strength generated by the electrical charge on the two plates or sheets of the conductor is back to normal.
If the electric field strength generated by the electrical charge on both conductor plates is reduced, the electric potential between the two conductor plates is also reduced. Because the electric field is directly proportional to the electric potential as stated in the equation E = V / d, where E = electric field, V = electric potential and d = distance between the two plates. If before there is an electric potential to the dielectric is Vo then after the dielectric, the electric potential is reduced to V by factor K.
Mathematically, Vo = K V or V = Vo / K or K = Vo / V, where K = dielectric constant. Vo> V so that K> 1.
Kindly note that the amount of the electric charge on both plates or sheets of conductors does not change so that the amount of the final charge is equal to the amount of the initial charge (Q = Qo). The change in capacitance of the capacitor is calculated in the following way:
C = final capacitance, Co = initial capacitance, Q = final charge, Qo = initial charge, V = final potential, Vo = initial potential, K = dielectric constant
Based on the equation above, it is concluded that the initial capacitance (Co) is smaller while the final capacitance (C) is greater. Capacitance increases by a factor of K, where K is the dielectric constant. The value of the dielectric constant of each insulating material varies. The dielectric constant (K) is the result of the ratio of the capacitance of the capacitor when using a dielectric, to the capacitance of the capacitor when not using a dielectric.
The dielectric increase capacitance because the distance between the two conductor plates decreases
Another dielectric function is to reduce the distance (d) between the two conductor plates. So that the electric field (E) and the electric voltage (V) between the two plates or sheets of conductors increase, as stated by the equation E = V / d. If the electric field and the electric voltage between the two plates or sheets increase, then the capacitance of the capacitor increases.
If the capacitor in question is parallel, the capacitance is calculated using the following formula:
Based on the two formulas above, it can be concluded that the capacitance (C) of the parallel plate capacitors can be enlarged by reducing the distance between the two plates or conductor sheets (d).
The dielectric increase capacitance because the capacitance of the capacitor increases
The dielectric is made of insulating material which, if it is in a strong electric field, will be damaged. Dielectric damage occurs when the electric field is so strong that it can move electrons off the atom, then the electrons hit electrons on other atoms so that the flow of electrons in the dielectric occurs. In other words, dielectric damage causes the dielectric which is an electric insulator to turn into an electric conductor.
To avoid damage, every dielectric made from a certain insulating material has a maximum electric field value that can be held, called dielectric strength. The dielectric strength of the insulating material is greater than the dielectric strength of the air and each insulating material has a different dielectric strength, some are small and some are large. So if a dielectric that has a large dielectric strength is used, the electric field that can be held is greater and the voltage that can be held is also greater. If the electric field and the electric voltage generated by the two plates or sheets of the conductor are greater, the greater the amount of electric charge that can be accommodated by the conductor plate. The more charge that is inside the conductor plate, the greater the capacitance of the capacitor.