Dielectric And Its Effects

formula

Energy in the electric field in a dielectric

U = \frac{1}{2} C V^{2} = \frac{1}{2} \frac{K ϵ _{0} A}{d} V^{2}

where

K

is the dielectric constant

definition

Dielectric

Dielectrics are non-conducting substances which are the insulating materials and are bad conductor of electric current.
Mica, Plastics, Glass, Porcelain and Various Metal Oxides and even dry air is also example of dielectric.

definition

Dielectric constant

The ratio of permittivity of a medium to the permittivity of free space is known as the dielectric constant or relative permittivity of the medium. It is denoted by

ε_{r}

K

K = \frac{ε}{ε _{o}}

Note:

K \geq 1

where

K = 1

for free space

definition

Dielectric Constant

n parallel plate capacitor, when dielectric slab is placed between the two plates then the ratio of the applied electric field strength to the strength of the reduced value of electric field capacitor is called dielectric constant that is:

K = \frac{E _{o}}{E}

K = Dielectric constant

E_{o} = D i e l e l c t r i c

E = Net Field

definition

Effect of dielectric on capacitance

The larger the dielectric constant, the more charge can be stored. Completely filling the space between capacitor plates with a dielectric increases the capacitance by a factor of the dielectric constant
C = KC'
Where C= New capacitance after introduction of dielectric
C' = Capacitance with no dielectric between the plates.

definition

Effect of electric field on dielectric material

Dielectric are non-conducting substances and have negligible number of charge carriers.
When a conductor is placed in an external electric field, free charges move such that the net field inside the conductor is zero. This is not possible in a dielectric.
In a dielectric, the electric field induces dipole moment by reorienting the molecules of the dielectric. This causes an electric field opposing the external electric field. Hence, the electric field inside a dielectric is smaller than the original electric field.

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Properties of Dielelctrics

1. Dielectrics does not have any free charges.
2. When an electric field is applied there is small displacement of bound charges creating small electric dipoles within the dielectric. This phenomenon is called Polarization.
3. The electric field inside and outside a dielectric gets modified due to presence of dipoles.
4. Dielectrics can store energy.

definition

Polar dielectric

If in any dielectric substance the centre of positive charge and centre of negative charge of each molecule do not coincide, then such type of dielectric material is called polar dielectric.
Ex : water and HCl

definition

Non-polar dielectric

If in a substance the centre of positive charge and centre of negative charge of each molecule coincide with each other, because of symmetry of molecules, then these substances are called non-polar dielectric substances.
Ex:

N_{2}, O_{2}, H_{2}

etc.

formula

Energy in the electric field in a dielectric

definition

Dielectric

definition

Dielectric constant

definition

Dielectric Constant

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Effect of dielectric on capacitance

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Effect of electric field on dielectric material

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Properties of Dielelctrics

definition

Polar dielectric

definition

Non-polar dielectric

Quick Summary With Stories

Introduction to Dielectrics

Polarisation of Dielectrics - Basic

Polarisation of Dielectrics II