Dielectric in a capacitor #4

Dielectric in a capacitor increase the potential energy of the capacitor. This happens due to polarization of the dielectric material. The polarized dielectric helps the capacitor to store more charge and therefore increase the electric field value across the capacitor plates. High electric field means more voltage and more voltage across plates increases the stored potential energy.
Dielectric material have dielectric strength that determines the factor by which the capacitors energy can be increased. Dielectric constant is a number that is used as a measure of this strength. Higher dielectric strength means more energy storage on capacitor. E.g water dielectric constant is 78.2 while that of mylar is 3.1. Then if dielectric constant of water is 78.2 but still it is not used as a dielectric. The reason for this is that the dielectric constant of water changes with motion of the water. In other words, the capacitance of the capacitor will constantly vary with motion of water. Thus even though dielectric constant of water is 78.2, it is a bad dielectric medium

00:22 How is a capacitor made?
00:59 How do dielectrics improve capacitor performance?
02:53 What happens when you put a dielectric between capacitor plates?
04:55 What is a dielectric constant?
05:52 Dielectric constants for various materials
06:20 How charge is induced in dielectric
09:27 What is permittivity of a dielectric
10:55 How does polarization of dielectric happen?
12:50 Visual representation - what happens when a dielectric is put between capacitor plates
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Dielectrics in a capacitors (Summary)
In simple terms, dielectric is the insulating material that separates two metallic plates of a capacitor. When electric field is applied to the capacitor plates, the dielectric gets polarized. This in turn helps in increasing the surface charge on the capacitor plates. Any increase in charge results in increasing the potential energy of the capacitor.

Transcript
In this lesson we will cover - what are dielectrics, what is dielectric constant, what is polarization of dielectric material and finally a visually representation of how introduction of dielectric changes the electric field, voltage and energy of a capacitor.

So, capacitors used in various applications have 2 long strips of metal foil separated by a plastic sheet that could be made of manganese or mylar or some other material….and then this combination is rolled up to a compact unit that can provide the required capacitance and energy

Now… the question that should come to your mind is why do we need to insert a plastic strip… that we call a dielectric, between the two metal foils. Well there are 3 benefits of doing this-
One, it is almost impossible to have two metal foils or plates separated by a thin layer of air since they would tend to collapse or come in contact with each other and we do not want that to happen. So this plastic layer neatly separates the two metallic plates.

Two, when you have air between the metal plates… there is a limit to which the capacitor can be charged or potential difference created and therefore a limit to which charge can be loaded and energy stored. Now the limit is on account of the build up of charge and therefore the electric field between the plates that when it reaches a certain value, it breaks down the air and tends to ionizes it. Now if the air gets ionized, it would permit movement of electrons directly through the space between the plates and that is something we do not want to happen

But, when you put a dielectric between the plates, the material can tolerate the strong electric field and does not ionize or more technically speaking, avoid an electric breakdown to a larger extent. As a result, you can charge up the capacitor a lot more and therefore have more energy packed into it. But then you got to remember that every capacitor with a dielectric still has a limit to which it can be subjected to a voltage or potential difference between the plates beyond which it will burn up … and you can actually see this limit printed on a capacitor

The third reason is that the capacitance of a capacitor with given dimensions goes up when you put a dielectric between the plates compared to vacuum.

#dielectric_constant #capacitors #IITJEEpreparations #jeestrategies #JEEMain2021 #jeemains2021 #AP_Physics

[TheScienceCube]

00:22​ How is a capacitor made?
00:59​ How do dielectrics improve capacitor performance?
02:53​ What happens when you put a dielectric between capacitor plates?
04:55​ What is a dielectric constant?
05:52​ Dielectric constants for various materials
06:20​ How charge is induced in dielectric
09:27​ What is permittivity of a dielectric
10:55​ How does polarization of dielectric happen?
12:50​ Visual representation - what happens when a dielectric is put between capacitor plates

[TheScienceCube]

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