Introduction to dielectrics

Capacitors have been used to store electrical energy since the late 18th century.

Benjamin Franklin was the first who used a series of capacitors for storing electrical energy.

And later we found that that the charge storing capacity of the capacitor can be increased with the help of dielectric substance.

Now, we will study the dielectric of the capacitor.

Let's see the introduction to the dielectric.

Let's consider that we have a conductor and it is placed inside the electric field.

And inside the conductor, there is a large number of the free electron which is responsible for the flow of current inside the conductor.

In presence of the electric field, all free electrons attracted towards the positive terminal and proton towards the negative terminal.

And as the direction of the electric field is from the positive terminal to the negative terminal.

Therefore all the free electron and proton will accommodate as shown in the figure,

And because of new charge distribution, there will be induced electric field generated inside the conductor.

And the redistribution of charges till the will equal to .

Hence, the net electric field on the conductor will be zero.

Next, consider an insulator molecule which does not allow the flow of current.

And in the insulator, there are no free electrons and due to this, there is no flow of current.

And when this insulator is placed inside the external electric field, then there will only some displacement of charges.

And again due to the displacement of charges, there is an induced an internal electric field . But its magnitude will be very small.

The net electric field on the insulator is given as,

So, we observe that there is a finite electric field on the insulator but its magnitude is less than .

So, the dielectric is defined as it is an insulator material that slightly displaces its charges in the presence of an external electric field in such a way to decrease the external electric field.

Next, we will study the types of dielectric material.

The dielectric is of two types as shown in the figure,

The polar dielectric is defined as if the centre of mass of the positive charge and negative charge does not coincide then it is polar dielectric.

Water is the example of polar dielectric because its centre of mass of the positive charge and negative charge does not coincide.

Further the net dipole of is shown as,

The non polar dielectric is defined as if the centre of mass of the positive charge and negative charge does coincide .

And the example for non polar dielectric is because its centre of mass of the positive charge and negative charge does coincide.

Let's conclude all the imortant points which we have studied.

Revision

The net electric field on the conductor will be zero if we placed in the external magnetic field.

Dielectric is defined as it is an insulator material that slightly displaces its charges in the presence of an external electric field in such a way to decrease the external electric field.

The dielectric is of two types as shown in the figure,

The End