When air is replaced by a dielectric medium of force constant K, the maximum force of attraction between two charges, separated by a distance :

In air the force of attraction between two charges is \\(\displaystyle F_a=\dfrac{1}{4\pi\epsilon_0} \frac{q_1q_2}{r^2}\\)In dielectric medium the force of attraction between two charges is \\(\displaystyle F_d=\dfrac{1}{4\pi K\epsilon_0} \dfrac{q_1q_2}{r^2}=\dfrac{F_a}{K}\\)Thus, force decreases K-times.

Two identical charged spheres are suspended by strings of equal lengths. The strings make an angle of \\(30^{0}\\) with each other. When suspended in a liquid of density 0.8 \\(\mathrm{g}\mathrm{c}\mathrm{m}^{-3}\\), the angle remains the same. lf density of the material of the sphere is 1.6 \\(\mathrm{g}\mathrm{c}\mathrm{m}^{-3}\\), the dielectric constant of the liquid is:

From fig,\\(tan\theta= qE/mg\\)\\(tan15^o=\dfrac{k q^2}{d^2 mg}\\)\\(tan15^o=\dfrac{k q^2}{1.6 Vgd^2 }\\) .....[\\(V\\) is the volume]...........(1)When system is suspended in liquid,\\(tan15^o=\dfrac{k q^2}{K(mg- \rho Vg)d^2 }\\) \\(tan15^o=\dfrac{k q^2}{K(1.6-0.8)Vgd^2 }\\) ......(2) from (1) and (2) we get,\\(\dfrac{k q^2}{K(1.6-0.8)Vgd^2 }\\)\\(=\dfrac{k q^2}{1.6 Vgd^2 }\\) \\(\therefore K=2=\\)Dielectric constant of liquid.

The force between two identical charges placed at a distance of \\(r\\) in vacuum is \\(F\\). Now, a slab of dielectric of constant \\(4\\) is inserted between these two charges. If the thickness of the slab is \\(\cfrac r2\\), then the force between the charges will become :

in vacuum, \\(F=\cfrac { 1 }{ 4\pi { \varepsilon }_{ 0 } } \cfrac { { q }^{ 2 } }{ { r }^{ 2 } } .....(i)\\)Suppose, force between the charges is same when charges are \\(r'\\) distance apart in dielectric.\\(F'=\cfrac { 1 }{ 4\pi { \varepsilon }_{ 0 } } \cfrac { { q }^{ 2 } }{ { kr' }^{ 2 } } .......(ii)\\)From \\((i)\\) and \\((ii)\\), \\(k{r'}^{2}={r}^{2}\\) or \\(r=\sqrt {kr'}\\)In the given situation, force between the charges would be\\(\quad F'=\cfrac { 1 }{ 4\pi { \varepsilon }_{ 0 } } \cfrac { { q }^{ 2 } }{ { \left( \cfrac { r }{ 2 } +\sqrt { 4 } \cfrac { r }{ 2 } \right) }^{ 2 } } =\cfrac { 4 }{ 9 } \cfrac { { q }^{ 2 } }{ 4\pi { \varepsilon }_{ 0 }{ r }^{ 2 } } =\cfrac { 4F }{ 9 } \\)

What are polar and non polar dielectric ,give one example each other ?Define di-electric constants.

NON POLAR DIELECTRICS:Are made of non-polar molecules.The center of mass of positive charges coincides with the center of mass of the negative charges, in the molecule.In its normal state (i.e., in the absence of any external force, esp electric field), each molecule has zero dipoles andhas a symmetric shape.POLAR DIELECTRICS:Are made of polar molecules.The center of mass of positive charges does not coincide with the center of mass of the negative charges, in the molecule.In its normal state (i.e., in the absence of any external force, esp electric field), each molecule has some intrinsic permanent dipole andhas an asymmetric shape.The dielectric constant is the ratio of the permittivity of a substance to the permittivity of free space. It is an expression of the extent to which a material concentrates electric flux, and is the electrical equivalent of relative magnetic permeability.

Define dielectric constant of a medium. What is its \\(S.I\\). unit?

The Dielectric constant (K) of the medium is the ratio of the permittivity of the substance (\varepsilon) to permittivity of the free space \\(\left( \varepsilon _ { 0 } \right) .\\)i.e \\(\mathrm { K } = \varepsilon / \varepsilon _ { 0 }\\)As Permittivity of medium and permittivity of free space both have same units(F/m ie Farad/meter) dielectric constant becomes dimensionless quantity.

Define the relative permittivity of a medium.

The amount by which the force between the charge (in presence of medium) is relatively less than that in a vacuum, is called the dielectric constant of that medium or relative permittivity (\\(\epsilon_r\\))\\(\epsilon_r=\dfrac{\text{Force between charges in air or vaccum}}{\text{Force between charges in medium}}\\)\\(\therefore\,\,\varepsilon_r=\dfrac{\varepsilon}{\varepsilon_0}\\)

Dielectric constant for a metal is:

Permittivity of metals is very high comparable to the permittivity of free space. So dielectric constant for metal is infinite.

Advanced Knowledge of Polarisation of Dielectrics

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

formula

Electric field due to a point charge placed in an infinite dielectric

E = \frac{q}{4 π ϵ _{0} r ^{2} K}

where

q

is the point charge placed inside an infinite dielectric and

r

is the distance at which the electric field is calculated.

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

Permittivity and relative permittivity

E = \frac{E _{0}}{K}

where

K

is the relative permittivity,

E

is the resultant electric field and

E_{0}

is the applied electric field.
The permittivity is

ε = ϵ_{0} K

definition

Electric polarization of matter

Polarization occurs when an electric field distorts the negative cloud of electrons around positive atomic nuclei in a direction opposite the field. By inducing the movement of electrons within an object, one side of the object is left with an excess of positive charge and the other side of the object is left with an excess of negative charge. Charge becomes separated into opposites.The polarization process always involves the use of a charged object to induce electron movement or electron rearrangement.

definition

Dielectric strength

The maximum electric field that a dielectric medium can withstand without breakdown (of its insulating property) is called its dielectric strength.
For air, it is

3 \times 1 0^{6} V / m

This puts a restriction on the value of capacitance of a given size and is the reason why capacitors are in the range of

μ F

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.

definition

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.

Advanced Knowledge of Polarisation of Dielectrics

formula

Energy in the electric field in a dielectric

formula

Electric field due to a point charge placed in an infinite dielectric

definition

Dielectric

definition

Permittivity and relative permittivity

definition

Electric polarization of matter

definition

Dielectric strength

definition

Dielectric Constant

definition

Effect of dielectric on capacitance

definition

Effect of electric field on dielectric material

definition

Properties of Dielelctrics

definition

Polar dielectric

definition

Non-polar dielectric

REVISE WITH CONCEPTS

Dielectrics-Polar and Non-polar Dielectric Molecules

Basic Knowledge of Polarisation of Dielectrics

Quick Summary With Stories

Polarisation of Dielectrics II

Introduction to Dielectrics

When air is replaced by a dielectric medium of force constant K, the maximum force of attraction between two charges, separated by a distance :

The force between two identical charges placed at a distance of $r$ in vacuum is $F$ . Now, a slab of dielectric of constant $4$ is inserted between these two charges. If the thickness of the slab is $\frac{r}{2}$ , then the force between the charges will become :

What are polar and non polar dielectric ,give one example each other ?Define di-electric constants.

Define dielectric constant of a medium. What is its $S . I$ . unit?

Define the relative permittivity of a medium.

Dielectric constant of pure water is $81$ . Its permittivity will be

The ratio of the forces between two small spheres with constant charges, in air and in a medium of dielectric constant $K$ , is

Dielectric constant for a metal is:

The dielectric constant $K$ of an insulator can be

formula

Energy in the electric field in a dielectric

formula

Electric field due to a point charge placed in an infinite dielectric

definition

Dielectric

definition

Permittivity and relative permittivity

definition

Electric polarization of matter

definition

Dielectric strength

definition

Dielectric Constant

definition

Effect of dielectric on capacitance

definition

Effect of electric field on dielectric material

definition

Properties of Dielelctrics

definition

Polar dielectric

definition

Non-polar dielectric

REVISE WITH CONCEPTS

Dielectrics-Polar and Non-polar Dielectric Molecules

Basic Knowledge of Polarisation of Dielectrics

Quick Summary With Stories

Polarisation of Dielectrics II

Introduction to Dielectrics

When air is replaced by a dielectric medium of force constant K, the maximum force of attraction between two charges, separated by a distance :

The force between two identical charges placed at a distance of r in vacuum is F. Now, a slab of dielectric of constant 4 is inserted between these two charges. If the thickness of the slab is 2r​, then the force between the charges will become :

What are polar and non polar dielectric ,give one example each other ?Define di-electric constants.

Define dielectric constant of a medium. What is its S.I. unit?

Define the relative permittivity of a medium.

Dielectric constant of pure water is 81. Its permittivity will be

The ratio of the forces between two small spheres with constant charges, in air and in a medium of dielectric constant K, is

Dielectric constant for a metal is:

The dielectric constant K of an insulator can be

The force between two identical charges placed at a distance of $r$ in vacuum is $F$ . Now, a slab of dielectric of constant $4$ is inserted between these two charges. If the thickness of the slab is $\frac{r}{2}$ , then the force between the charges will become :

Define dielectric constant of a medium. What is its $S . I$ . unit?

Dielectric constant of pure water is $81$ . Its permittivity will be

The ratio of the forces between two small spheres with constant charges, in air and in a medium of dielectric constant $K$ , is

The dielectric constant $K$ of an insulator can be