Chapter - 1 : DiElectrics
Q-1: What Is Dielectrics? Explain.
Ans: Defination:
A Dielectric is an Electrical Insulator that can be Polarized by an Applied Electric Field.
⦁ At Certain Potential Difference,Materials Such As Glass,Rubber,Wood etc. Provides Electric Insulation between Two Condutors.
⦁ Under Certain Circumstance(situation or condition),They Are Used For Storing Electrical Charge.
⦁ Dielectrics Materials Are Non-Conducting Materials because all electron are tightly bound with the Nucleus of an Atom.
⦁ The Dielectrics are Non-metallic materials of High Specific Resitance & have Negative Temperature Co-efficient of Resistance.
Q-2: Polarization Of Dielectric.
Ans: Definition:
Polarization Of Dielectric is Used To Describe The Behaviour of a Material When An External Electric field is applied on it.
Explanation:
Figure:
Thus Polarization is defined as the process of inducing Dipoles In Dielectric Material by an External Electric Field.
The DiElectrics Are Classified Into Two Categories:
1. Polar Dielectric
2. Non-Polar Dielectric
1. Polar Dielectric:
A Dielectric material in which there is a permanent Dipole Exists in Absence of external field is called Polar Dielectric.
ex: H2O,HCl & CO.
2. Non-Polar Dielectric:
A Dielectric material in which there is No permanent Dipole Exists in Absence of external field is called Non-Polar Dielectric.
ex: H2,N2,O2,CO2 etc.
Relative Permittivity: It Is Defined As The Ratio Of "Permittivity Of The Medium (ε)" To The "Permittivity of Free Space(ε0).
i.e., εr= ε/ε0
Electric Field (E): The Field or Space around a Charge Particle where its Force can be experienced by any other Charged particle is called the Electric Field.
Electric Flux(Ï•): The Number Of Line Of Force That Pass Through A Surface Placed In The Vector Field.
Electric Flux Density(D): Flux Passing Per Unit Area Is Called Electric Flux Density.
Polarization Vector (P): It Is Defined As The Induced Dipole Moment Per Unit Volume Of Dielectric Material.
Q-3: Clausius Mossotti Equation.
Ans:
Q-4: Types Of Dielectric Materials.
Ans: There Are Three Types Of Dielectric Materials:
1: Solid
2: Liquid
3: Gaseous
⦁ Mica is An Inorganic Mineral Material.
⦁ It Is Crystalline in Nature.
⦁ It is Rigid,Tough & Strong.
⦁ It has high Dielectric Strength & Low Dielectric Loss.
2: Glass:
⦁ Glass is An Inorganic Material.
⦁ Glass is Brittle & Hard.
⦁ It Has Good Mechanical Strength & Low Dielectric Loss.
⦁ It Is Used As A Dielectric in Capacitors.
3: Asbestos:
⦁ It is Naturally Occuring mineral material.
⦁ It is Fibrous In Nature.
⦁ It generally Consists Of Magnesiums Silicate.
1: Mineral Insulating Oils:
⦁ These Oils Are Obtained From Crude Petroleum by Distillation.
⦁ It is Stable,biodegradable,High viscosity,inactive oil.
⦁ It is Used In Transformers And Capacitors.
⦁ It is used for insulation and cooling transformers.
2: Synthetic Instulating oils:
⦁ Synthetic Oils are very much resistance to oxidation and to fire hazards.
⦁ It is Used As a Coolants and insulators in high voltage.
3: Miscellaneous Insulating oils:
⦁ Vaseline,vegetable oils and silicons liquids belong to this category.
⦁ It is used in High Voltage Transformers.
⦁ It has High Viscosity and Dielectric Constant.
1: Air:
⦁ Air Is a Dielectric Material.
⦁ The Dielectric Loss Is Zero.
⦁ It is used as a dielectric in Condenser(Air Condenser).
2: Nitrogen:
⦁ It is a gaseous Dielectric.
⦁ It is Chemically Invert.
⦁ It Prevent From Oxidation.
3: Sulphur Hexafluoride:
⦁ It is formed by burnig of sulphur in fluorine atmosphere.
⦁ It has superior cooling properties.
⦁ It is used in Transformer,electric switch,van de graff generator etc.
Q-5: Properties Of A Good Dielectric Material.
Ans:
1. It Should have High Resistivity To Reduce leakage current.
2. It Should have high dielectric strength.
3. It Should have high Mechanical strength.
4. It Should have high Fire Resistance.
5. It Should have high chemical inertness.
6. It Should have high thermal conductivity.
7. It Should have low dielectric loss.
8. It Should have low thermal expansion.
Ans: Defination:
A Dielectric is an Electrical Insulator that can be Polarized by an Applied Electric Field.
⦁ At Certain Potential Difference,Materials Such As Glass,Rubber,Wood etc. Provides Electric Insulation between Two Condutors.
⦁ Under Certain Circumstance(situation or condition),They Are Used For Storing Electrical Charge.
⦁ Dielectrics Materials Are Non-Conducting Materials because all electron are tightly bound with the Nucleus of an Atom.
⦁ The Dielectrics are Non-metallic materials of High Specific Resitance & have Negative Temperature Co-efficient of Resistance.
Q-2: Polarization Of Dielectric.
Ans: Definition:
Polarization Of Dielectric is Used To Describe The Behaviour of a Material When An External Electric field is applied on it.
Explanation:
- When An External Field Is Applied,it causes the electron cloud to move away.
- Thus,the centroids of the positive and negative charges now no longer coincide and as a result an Electric Dipole is Induced in an Atom.
- Thus, The Atoms are said to be Polarized.
Figure:
Thus Polarization is defined as the process of inducing Dipoles In Dielectric Material by an External Electric Field.
The DiElectrics Are Classified Into Two Categories:
1. Polar Dielectric
2. Non-Polar Dielectric
1. Polar Dielectric:
A Dielectric material in which there is a permanent Dipole Exists in Absence of external field is called Polar Dielectric.
ex: H2O,HCl & CO.
2. Non-Polar Dielectric:
A Dielectric material in which there is No permanent Dipole Exists in Absence of external field is called Non-Polar Dielectric.
ex: H2,N2,O2,CO2 etc.
Some Basic Definations:
Relative Permittivity: It Is Defined As The Ratio Of "Permittivity Of The Medium (ε)" To The "Permittivity of Free Space(ε0).
i.e., εr= ε/ε0
Electric Field (E): The Field or Space around a Charge Particle where its Force can be experienced by any other Charged particle is called the Electric Field.
Electric Flux(Ï•): The Number Of Line Of Force That Pass Through A Surface Placed In The Vector Field.
Electric Flux Density(D): Flux Passing Per Unit Area Is Called Electric Flux Density.
Polarization Vector (P): It Is Defined As The Induced Dipole Moment Per Unit Volume Of Dielectric Material.
Q-3: Clausius Mossotti Equation.
Ans:
Q-4: Types Of Dielectric Materials.
Ans: There Are Three Types Of Dielectric Materials:
1: Solid
2: Liquid
3: Gaseous
Solid Dielectric:
1: Mica:⦁ Mica is An Inorganic Mineral Material.
⦁ It Is Crystalline in Nature.
⦁ It is Rigid,Tough & Strong.
⦁ It has high Dielectric Strength & Low Dielectric Loss.
2: Glass:
⦁ Glass is An Inorganic Material.
⦁ Glass is Brittle & Hard.
⦁ It Has Good Mechanical Strength & Low Dielectric Loss.
⦁ It Is Used As A Dielectric in Capacitors.
3: Asbestos:
⦁ It is Naturally Occuring mineral material.
⦁ It is Fibrous In Nature.
⦁ It generally Consists Of Magnesiums Silicate.
Liquid Dielectric:
1: Mineral Insulating Oils:
⦁ These Oils Are Obtained From Crude Petroleum by Distillation.
⦁ It is Stable,biodegradable,High viscosity,inactive oil.
⦁ It is Used In Transformers And Capacitors.
⦁ It is used for insulation and cooling transformers.
2: Synthetic Instulating oils:
⦁ Synthetic Oils are very much resistance to oxidation and to fire hazards.
⦁ It is Used As a Coolants and insulators in high voltage.
3: Miscellaneous Insulating oils:
⦁ Vaseline,vegetable oils and silicons liquids belong to this category.
⦁ It is used in High Voltage Transformers.
⦁ It has High Viscosity and Dielectric Constant.
3: Gaseous Dielectric:
⦁ Air Is a Dielectric Material.
⦁ The Dielectric Loss Is Zero.
⦁ It is used as a dielectric in Condenser(Air Condenser).
2: Nitrogen:
⦁ It is a gaseous Dielectric.
⦁ It is Chemically Invert.
⦁ It Prevent From Oxidation.
3: Sulphur Hexafluoride:
⦁ It is formed by burnig of sulphur in fluorine atmosphere.
⦁ It has superior cooling properties.
⦁ It is used in Transformer,electric switch,van de graff generator etc.
Q-5: Properties Of A Good Dielectric Material.
Ans:
1. It Should have High Resistivity To Reduce leakage current.
2. It Should have high dielectric strength.
3. It Should have high Mechanical strength.
4. It Should have high Fire Resistance.
5. It Should have high chemical inertness.
6. It Should have high thermal conductivity.
7. It Should have low dielectric loss.
8. It Should have low thermal expansion.
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